Preventing Lubuntu 18.04 from leaving a user process running after the user logs out

My family’s desktop machine has Lubuntu 18.04 installed, which uses systemd and the LXDE desktop environment. Each family member has their own user account, thus the installation is a single-seat, multi-user installation. For each user’s account I set up the virus-checking scheme described in an earlier post, suitably modified to take into account the differences between Lubuntu 18.04 and Gentoo Linux running KDE. For example, the monitorDownloadsGUI script in Lubuntu 18.04 uses zenity rather than kdialog, and, as Lubuntu 18.04 uses systemd, the ClamAV daemon’s service file in Lubuntu 18.04 is /lib/systemd/system/clamav-daemon.service rather than the OpenRC init file /etc/init.d/clamd used in my Gentoo Linux installations.

The virus-checking script ~/.monitorDownloadGUI in each user’s home directory is launched automatically by LXDE at login because I created a Desktop Configuration File ~/.config/autostart/monitorDownloadsGUI.desktop in each user’s account. For example, the contents of the file in my account are as follows:

[Desktop Entry]
Type=Application
Exec=/home/fitzcarraldo/.monitorDownloadsGUI

However, I recently noticed that Lubuntu 18.04 does not terminate the monitorDownloadsGUI process when the user logs out. I do not see this behaviour on my laptops running Gentoo Linux with OpenRC and KDE, so I am not sure why this is happening in Lubuntu 18.04 with systemd and LXDE. The output of the ‘ps -ef‘ command after each of the three example steps shown below illustrates the behaviour.

Step 1. george is the only user who is logged-in.

$ ps -ef | grep bash | grep -v grep
george    1410     1  0 02:05 ?        00:00:00 /bin/bash /home/george/.monitorDownloadsGUI
george    1597  1358  0 02:05 pts/0    00:00:00 /bin/bash

Step 2. ringo uses ‘Logout’ > ‘Switch User’ to login to his account.

$ ps -ef | grep bash | grep -v grep
george    1410     1  0 02:05 ?        00:00:00 /bin/bash /home/george/.monitorDownloadsGUI
george    1597  1358  0 02:05 pts/0    00:00:00 /bin/bash
ringo     2382     1  0 02:06 ?        00:00:00 /bin/bash /home/ringo/.monitorDownloadsGUI

Step 3. ringo logs out of his account.

$ ps -ef | grep bash | grep -v grep
george    1410     1  0 02:05 ?        00:00:00 /bin/bash /home/george/.monitorDownloadsGUI
george    1597  1358  0 02:05 pts/0    00:00:00 /bin/bash
ringo     2382     1  0 02:06 ?        00:00:00 /bin/bash /home/ringo/.monitorDownloadsGUI

Notice that the process with PID 2382 is still running, even though user ringo is no longer logged in.

If a user logs out and logs in again, or if users switch between sessions using ‘Logout’ > ‘Switch User’, it is also possible for multiple instances of the script per user to be running. For example:

$ ps -ef | grep bash | grep -v grep
george    1564     1  0 11:14 ?        00:00:00 /bin/bash /home/george/.monitorDownloadsGUI
ringo     2522     1  0 11:16 ?        00:00:00 /bin/bash /home/ringo/.monitorDownloadsGUI
george    3803     1  0 11:17 ?        00:00:00 /bin/bash /home/george/.monitorDownloadsGUI
george    5997     1  0 11:19 ?        00:00:00 /bin/bash /home/george/.monitorDownloadsGUI
george    6054  5881  0 11:19 pts/0    00:00:00 /bin/bash

Notice that several instances of the script are running for user george. There should only be one instance.

In order to prevent these multiple instances, I added the shell script lines below to the existing LightDM session-cleanup-script that I had created previously to solve a different problem in the Lubuntu 18.04 installation (see an earlier blog post).

# Get rid of duplicate instances (if any) per user of the virus-checker script's process
who -u | grep -v "\." > /tmp/logged-in_users
while IFS=: read -r f1 f2 f3 f4 f5 f6 f7
# $f1 is username
# $f2 is password ('x')
# $f3 is UID
# $f4 is GID
# $f5 is UID info
# $f6 is home directory
# $f7 is command/shell
do
    match=0
    while read a b c d e f g h # Use this if this script is launched by LightDM in Lubuntu 18.04
#    while read a b c d e f g # Use this if you launch this script from a terminal in Lubuntu 18.04
    #
    # If this script is launched by a user, 'who -u' returns the following fields:
    # "john     tty7         2019-08-31 17:08 00:01        1624 (:0)"
    # If this script is launched by LightDM, 'who -u' returns the following fields:
    # "john     tty7        Aug 31 17:08 00:01        1624 (:0)"
    #
    do
        if [[ $f6 == *"/home/"* ]] && [[ $f7 == "/bin/bash" ]] && [[ $a == $f1 ]]; then
            match=1
            user=$f1
            tty=$b
        fi
    done < /tmp/logged-in_users
    if [[ $match -eq 1 ]] && [[ $(echo $tty | sed 's/[^0-9]*//g') -gt 6 ]]; then
        if [[ `ps -ef | grep bash | grep "$user" | grep monitorDownloadsGUI | awk -F' ' '{print $2}' | wc -l` -gt 1 ]]; then
            kill `ps -ef | grep bash | grep "$user" | grep monitorDownloadsGUI | awk -F' ' '{print $2}' | tail -n +2`
        fi
    elif [[ $match -ne 1 ]]; then
        if [[ $f6 == *"/home/"* ]] && [[ $f7 == "/bin/bash" ]] && [[ `ps -ef | grep bash | grep "$f1" | grep monitorDownloadsGUI | awk -F' ' '{print $2}' | wc -l` -gt 1 ]]; then
            kill `ps -ef | grep bash | grep "$f1" | grep monitorDownloadsGUI | awk -F' ' '{print $2}' | tail -n +2`
        elif [[ $f6 == *"/home/"* ]] && [[ $f7 == "/bin/bash" ]] && [[ `ps -ef | grep bash | grep "$f1" | grep monitorDownloadsGUI | awk -F' ' '{print $2}' | wc -l` -eq 1 ]]; then
            kill `ps -ef | grep bash | grep "$f1" | grep monitorDownloadsGUI | awk -F' ' '{print $2}'`
        fi
    fi
done < /etc/passwd
rm /tmp/logged-in_users

The above lines of Bash script kill additional instances of monitorDownloadGUI on a per-user basis when a user session ends. If LightDM’s session-cleanup-script does this, there will be no more than one instance of a monitorDownloadsGUI process per logged-in user, and no instances of a monitorDownloadGUI process for users who have logged out:

$ ps -ef | grep bash | grep -v grep
george    1473     1  0 12:32 ?        00:00:00 /bin/bash /home/george/.monitorDownloadsGUI
george    1693  1412  0 12:32 pts/0    00:00:00 /bin/bash

Problem solved. Well, worked around. I would like to know what causes the problem to happen in the first place. I assume it is either systemd or LXDE.

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How to stop inactive user sessions triggering Suspend to RAM in a single-seat, multi-user installation of Lubuntu 18.04

In my previous post I mentioned a problem that I had still not been able to fix in a single-seat, multi-user installation of Lubuntu 18.04: Xfce Power Manager in each user’s account can cause the installation to suspend to RAM if a user has not logged out of his/her session and another user is using a different session. Each user account in Lubuntu 18.04 has its own XfcePower Manager settings, stored in the file ~/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-power-manager.xml. If the property /xfce4-power-manager/inactivity-on-ac has a value of 15 (minutes) or higher, that session can cause the machine to suspend to RAM even if the session is not active while someone else’s session is active. The example below illustrates the effect.

Consider five users mick, christine, john, stevie and lindsey with the following settings for the number of minutes of inactivity that will trigger suspension to RAM:

mick@aspirexc600:~$ xfconf-query -c xfce4-power-manager -p /xfce4-power-manager/inactivity-on-ac
30
christine@aspirexc600:~$ xfconf-query -c xfce4-power-manager -p /xfce4-power-manager/inactivity-on-ac
25
john@aspirexc600:~$ xfconf-query -c xfce4-power-manager -p /xfce4-power-manager/inactivity-on-ac
45
stevie@aspirexc600:~$ xfconf-query -c xfce4-power-manager -p /xfce4-power-manager/inactivity-on-ac
15
lindsey@aspirexc600:~$ xfconf-query -c xfce4-power-manager -p /xfce4-power-manager/inactivity-on-ac
30

Now, suppose that john boots the machine, logs in to his account to check his e-mail, leaves the e-mail client open and goes off to grab lunch without logging out. Then stevie comes along and clicks on ‘Logout’ > ‘Switch User’ to display the LightDM greeter screen (or the greeter screen is already displayed because john‘s session has already been locked), logs in to her account and begins to use, say, LibreOffice Writer. Even though stevie is busy typing, the machine will suspend to RAM after 45 minutes of inactivity by john. This can be very annoying.

In addition to the individual users’ Xfce Power Manager configuration files in Lubuntu 18.04, I found the following Xfce Power Manager configuration files which appear to be system-wide:

/etc/xdg/xdg-Lubuntu/xfce4/xfconf/xfce-perchannel-xml/xfce4-power-manager.xml
/etc/xdg/xfce4/xfconf/xfce-perchannel-xml/xfce4-power-manager.xml

First attempt at fixing the problem

I asked all the users to configure their accounts to never cause the machine to suspend, by using the Xfce Power Manager settings GUI in their session and selecting ‘Never’. I noticed this caused each user’s /xfce4-power-manager/inactivity-on-ac property to become ‘14‘:

user $ xfconf-query -c xfce4-power-manager -p /xfce4-power-manager/inactivity-on-ac
14

Note that users must not edit their file ~/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-power-manager.xml; if they do, the settings shown in the Xfce Power Manager settings GUI will not be updated. Users must either use the Xfce Power Manager settings GUI or xfconf-query commands as explained on the askubuntu Web page ‘Change xfce4-power-manager option from terminal‘.

Then I edited the file /etc/xdg/xdg-Lubuntu/xfce4/xfconf/xfce-perchannel-xml/xfce4-power-manager.xml to make its contents the same as the previous contents of the individual users’ settings when Suspend to RAM was enabled individually):

<?xml version="1.0" encoding="UTF-8"?>

<channel name="xfce4-power-manager" version="1.0">
  <property name="xfce4-power-manager" type="empty">
    <property name="power-button-action" type="uint" value="3"/>
    <property name="show-tray-icon" type="bool" value="true"/>
    <property name="brightness-switch-restore-on-exit" type="int" value="1"/>
    <property name="brightness-switch" type="int" value="0"/>
    <property name="presentation-mode" type="bool" value="false"/>
    <property name="inactivity-on-ac" type="uint" value="30"/>
    <property name="blank-on-ac" type="int" value="10"/>
    <property name="dpms-on-ac-sleep" type="uint" value="0"/>
    <property name="dpms-on-ac-off" type="uint" value="0"/>
    <property name="brightness-on-ac" type="uint" value="9"/>
    <property name="lock-screen-suspend-hibernate" type="bool" value="true"/>
    <property name="logind-handle-lid-switch" type="bool" value="false"/>
    <property name="dpms-enabled" type="bool" value="false"/>
    <property name="general-notification" type="bool" value="true"/>
    <property name="sleep-button-action" type="uint" value="0"/>
    <property name="hibernate-button-action" type="uint" value="0"/>
  </property>
</channel>

After rebooting, leaving one or more users logged in without any activity did not cause the installation to suspend to RAM after 30 minutes of no activity in any session.

So I then edited the file /etc/xdg/xfce4/xfconf/xfce-perchannel-xml/xfce4-power-manager.xml to make its contents the same as the above. After rebooting, leaving one or more users logged in without any activity did not cause the installation to suspend to RAM after 30 minutes of no activity in any session.

I therefore assume that the above two files are ignored by Xfce Power Manager during normal operation.

Second attempt at fixing the problem

I used the procedure given in the Xfce4-power-manager FAQs to check if Xfce Power Manager in Lubuntu 18.04 uses systemd-logind to suspend the installation, and indeed it does:

TRACE[xfpm-polkit.c:366] xfpm_polkit_check_auth_intern(): Action=org.freedesktop.login1.suspend is authorized=TRUE

Therefore I edited /etc/systemd/logind.conf to add IdleAction=suspend and IdleActionSec=30min, and rebooted. However, this had no discernable effect either. Leaving one or more users logged in without any activity did not cause the installation to suspend to RAM after 30 minutes of no activity in any session.

Third attempt (successful) at fixing the problem

So, what to do?! In my previous post I explained how I had fixed the problem of not being able to suspend to RAM automatically from the LightDM greeter screen. I decided to keep the scripts from that post and add a new script sessions_sleep.sh to the root crontab. The contents of all the files and the crontab are shown below.

user $ cd /etc/lightdm/lightdm.conf.d/
user $ cat 10_lubuntu.conf 
[Seat:*]
greeter-setup-script=/etc/lightdm/lightdm.conf.d/lightdm_sleep.sh
session-setup-script=/etc/lightdm/lightdm.conf.d/lightdm_kill_sleep.sh
session-cleanup-script=/etc/lightdm/lightdm.conf.d/unmount_FREECOM_HDD.sh
user $ ls
05_lubuntu.conf  lightdm_kill_sleep.sh       sessions_sleep.sh
10_lubuntu.conf  lightdm_sleep.sh            unmount_FREECOM_HDD.sh
user $ cat lightdm_sleep.sh 
#!/bin/bash
# This forms part of the scheme to provide automatic suspension while the greeter screen is displayed
file="/tmp/unique_identifier"
(while true; do sleep 30m; systemctl suspend; done) &
echo $! > $file
user $ cat lightdm_kill_sleep.sh
#!/bin/bash
# This forms part of the scheme to provide automatic suspension while the greeter screen is displayed
file="/tmp/unique_identifier"
if [ -f "$file" ]; then
    kill `cat $file`
    rm $file
fi
user $ tail -n 11 unmount_FREECOM_HDD.sh
#----------------------------------------------------------------------------------------------------
#
# This forms part of the scheme to provide automatic suspension while the greeter screen is displayed
file="/tmp/unique_identifier"
if [ -f "$file" ]; then
    kill `cat $file`
    rm $file
fi
#
#----------------------------------------------------------------------------------------------------
exit 0

If the machine did not already have a permanently-connected external USB HDD (LABEL=”FREECOM HDD”) then it would have sufficed to specify a script named, for example, lightdm_kill_sleep2.sh instead of unmount_FREECOM_HDD.sh:

user $ cat 10_lubuntu.conf 
[Seat:*]
greeter-setup-script=/etc/lightdm/lightdm.conf.d/lightdm_sleep.sh
session-setup-script=/etc/lightdm/lightdm.conf.d/lightdm_kill_sleep.sh
session-cleanup-script=/etc/lightdm/lightdm.conf.d/lightdm_kill_sleep2.sh
user $ cat lightdm_kill_sleep2.sh
#!/bin/bash
# This forms part of the scheme to provide automatic suspension while the greeter screen is displayed
file="/tmp/unique_identifier"
if [ -f "$file" ]; then
    kill `cat $file`
    rm $file
fi
user $ sudo nano sessions_sleep.sh
user $ sudo chmod +x sessions_sleep.sh
user $ cat sessions_sleep.sh 
#!/bin/bash
while true
do
    # Only monitor idle time and suspend after specified inactivity if lightdm_sleep.sh is not taking care of those
    if [[ `ps -ef | grep bash | grep lightdm_sleep.sh | wc -l` -eq 0 ]]; then
        #-------------------------------STAGE 1: FIND OUT WHO IS THE ACTIVE USER--------------------------------------
        #
        while IFS=: read -r f1 f2 f3 f4 f5 f6 f7
        # $f1 is username
        # $f2 is password ('x')
        # $f3 is UID
        # $f4 is GID
        # $f5 is UID info
        # $f6 is home directory
        # $f7 is command/shell
        do
            if [[ $f6 == *"/home/"* ]] && [[ $f7 == "/bin/bash" ]]; then
                if `loginctl list-users | grep -ve '^$\|USER\|listed' | awk -F' ' '{print $2}' | grep -q $f1`; then
                    state=`loginctl show-user $f3 | grep State | awk -F'=' '{print $2}'`
                    if [[ $state != "active" ]]; then
                        inactive_user=$f1
                    elif [[ $state == "active" ]]; then
                        active_user=$f1
                    fi
                fi
            fi
        done < /etc/passwd
        #
        #-------------------------------STAGE 2: ASCERTAIN USER SESSIONS---------------------------------------------
        #
        # Find idle time for each X Windows session and suspend to RAM if the active user has been idle for >=30min.
        #
        who -u | grep -v "\." > /tmp/logged-in_users
        #
        while read a b c d e f g
        # $a is username
        # $b is the tty (tty1 to tty12)
        # $c is the date (yyyy-mm-dd)
        # $d is the time (hh:mm)
        # $e is the idle time (hh:mm) which does not reflect reality in this installation, for some reason
        # $f is the PID
        # $g is the display e.g. "(:1)"
        # Example: "john     tty7         2019-08-31 17:08 00:01        1624 (:0)"
        do
            if [[ $(echo $b | sed 's/[^0-9]*//g') -gt 6 ]]; then
                display=$(echo $g | sed 's/[^0-9]*//g')
                idle_millisecs=$(env DISPLAY=:$display sudo -u $a xprintidle)
                let idle_minutes=$idle_millisecs/60000
                if [[ $idle_minutes -ge 30 ]] && [[ $a == "$active_user" ]]; then
                    systemctl suspend
                fi
            fi
        done < /tmp/logged-in_users
        rm /tmp/logged-in_users
        #
        #------------------------------------------------------------------------------------------------------------
        sleep 10 # Frequency to repeat check
   fi
done

I installed the utility xprintidle via the Linux distribution’s package manager. As the name of the utility suggests, it returns the time (in milliseconds) that an X Windows session has been idle. Nice utility, by the way.

user $ sudo crontab -e
user $ sudo crontab -l | grep -v ^#
@reboot sudo /etc/lightdm/lightdm.conf.d/sessions_sleep.sh

Note that, despite its name, ‘@reboot‘ in the cron job will run the script after a cold boot as well as after a warm boot (reboot). Also note that the use of ‘sudo‘ in the root cron job is not an error; it makes the root cron job use the root user’s environment variables.

Remember that the property /xfce4-power-manager/inactivity-on-ac has to be configured to have a value of 14 (which corresponds to ‘Never’ in the Xfce Power Manager settings GUI) for every user. This should be done by each user using the Xfce Power Manager settings GUI in their own session.

Basically, the scheme works as follows: At boot, Lubuntu 18.04 launches the looping Bash script sessions_sleep.sh, which remains running but does nothing because no X Windows users are logged in. When LightDM runs the greeter-setup-script (lightdm_sleep.sh) and displays the greeter screen, sessions_sleep.sh still does nothing while lightdm_sleep.sh is running and taking care of managing suspension. When an X Windows user logs in and LightDM’s session-setup-script (lightdm_kill_sleep.sh) kills the running script lightdm_sleep.sh, the script sessions_sleep.sh then takes over monitoring users’ activity in X Windows and triggers suspension if the active user has not used his/her session for 30 minutes. If an X Windows user logs out, LightDM’s session-cleanup-script (unmount_FREECOM_HDD.sh) also kills lightdm_sleep.sh if it is running. When LightDM again runs its greeter-setup-script (lightdm_sleep.sh) and displays the greeter screen, that again inhibits sessions_sleep.sh from taking any action if no X Windows user is logged in. This all sounds convoluted, but it seems to work fine so far.

Because Xfce Power Manager is no longer used to monitor idle time and trigger suspension, ‘Presentation mode’ in Xfce Power Manager can no longer prevent the system from suspending after 30 minutes of inactivity while someone is watching a long video or playing music, for example. However this is not a problem; to temporarily inhibit suspension the user can use the method given in my earlier post ‘How to move a mouse pointer automatically in Linux to simulate user activity‘.

The Lubuntu 18.04 architecture

I suspect most Lubuntu 18.04 installations are on laptops or desktop machines with a single user, i.e. single-seat, single-user installations. In such a case, unless the user has created multiple user accounts that he/she logs into concurrently (by using ‘Switch User’, for example), the machine will never suspend unexpectedly while the user is logged in and using the session. I think the way LightDM, light-locker, systemd-logind and Xfce Power Manager have been bundled in Lubuntu 18.04 to manage suspending to RAM is a dog’s breakfast. The design apparently does not take into consideration that different people could be logged in concurrently in a single-seat installation. Try forcing people to log off so that only one person is ever logged in — it won’t happen! To be interrupted by Suspend to RAM triggered by Xfce Power Manager due to inactivity in a different session is illogical; the system should not suspend when someone is actively using the system. Therefore, in my opinion, management of suspension (and hibernation) ought to be configured and managed system-wide, not on a per-user basis, and a design should not require users to hack the installation to the extent I have described above. I was ‘scratching an itch’, but users should not have to jump through hoops to get an installation to function in a sensible manner. For all I know there may be a simpler way of achieving the functionality in Lubuntu 18.04 that I have described in this post and my previous post, but, if there is, it is not obvious. LightDM, light-locker, systemd and Xfce Power Manager are developed by different people, and functionality such as suspension and hibernation does not seem to have been considered using ‘helicopter vision’. Designing disparate applications developed separately to work together holistically is not a trivial task.

Anyway, hopefully I have fixed the problem and also ‘scratched my itch’. No more unexpected suspensions while I am using the family desktop machine!

How to make LightDM suspend to RAM automatically from the login screen and lock screen in Lubuntu 18.04

My family’s desktop machine has Lubuntu 18.04 installed, which generally works well. Each family member has their own account, therefore the installation is a single-seat, multi-user system. Lubuntu 18.04 uses LightDM for the display manager, light-locker (which uses LightDM) for the screen locker, and Xfce Power Manager for power management. Xfce Power Manager enables each user to specify for their session that the machine will suspend to RAM, and to configure the duration of inactivity in their session that will trigger suspension.

However, a couple of things about this arrangement are annoying. Firstly, if two or more users happen to be logged-in simultaneously because a family member does not bother to log out, Xfce Power Manager in an inactive session will eventually suspend the machine even when another user is actively using a different session. Secondly, if nobody is logged-in and the LightDM greeter screen is displayed, the machine will not suspend to RAM automatically after a period of inactivity. The only way to get the machine to suspend to RAM if nobody is logged-in is to click on the power indicator in the greeter’s system tray and select ‘Suspend’ from the drop-down menu.

I still have not figured out how to fix the first of the above-mentioned problems, but a Web search finally turned up a fix for the second problem: a post by Linux user boyi in Arch Linux Forums thread ‘need lightdm to suspend system‘. Below I explain how I implemented this in my family’s Lubuntu 18.04 installation. Basically, when the LightDM greeter screen is displayed LightDM runs a looping shell script (lightdm_sleep.sh) that will suspend the machine after a specified time has elapsed, and either logging in or unlocking the screen will run another shell script (lightdm_kill_sleep.sh) that kills the first script. Once a user has either logged in or unlocked the screen, Xfce Power Manager in that user’s session takes over monitoring activity.

1. Pre-existing situation
When I originally installed Lubuntu 18.04 I made sure each user used the Xfce Power Manager GUI to configure suspension to RAM. Each user’s own settings are shown below:

user $ cat ~/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-power-manager.xml
<?xml version="1.0" encoding="UTF-8"?>

<channel name="xfce4-power-manager" version="1.0">
  <property name="xfce4-power-manager" type="empty">
    <property name="power-button-action" type="uint" value="3"/>
    <property name="show-tray-icon" type="bool" value="true"/>
    <property name="brightness-switch-restore-on-exit" type="int" value="1"/>
    <property name="brightness-switch" type="int" value="0"/>
    <property name="presentation-mode" type="bool" value="false"/>
    <property name="inactivity-on-ac" type="uint" value="30"/>
    <property name="blank-on-ac" type="int" value="10"/>
    <property name="dpms-on-ac-sleep" type="uint" value="0"/>
    <property name="dpms-on-ac-off" type="uint" value="0"/>
    <property name="brightness-on-ac" type="uint" value="9"/>
    <property name="lock-screen-suspend-hibernate" type="bool" value="true"/>
    <property name="logind-handle-lid-switch" type="bool" value="false"/>
    <property name="dpms-enabled" type="bool" value="false"/>
    <property name="general-notification" type="bool" value="true"/>
    <property name="sleep-button-action" type="uint" value="3"/>
    <property name="hibernate-button-action" type="uint" value="3"/>
  </property>
</channel>

Note that each user must not edit their file ~/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-power-manager.xml directly, as the properties in the Xfce Power Manager settings GUI will not be updated if they do. Users must either use the Xfce Power Manager settings GUI or use xfconf-query commands on the command line as explained on the askubuntu Web page ‘Change xfce4-power-manager option from terminal‘.

The LightDM configuration files in /etc/lightdm/lightdm.conf.d/ were as follows:

user $ ls /etc/lightdm/lightdm.conf.d/
05_lubuntu.conf  10_lubuntu.conf  unmount_FREECOM_HDD.sh

The file 05_lubuntu.conf was installed when I installed Lubuntu 18.04. The two files 10_lubuntu.conf and unmount_FREECOM_HDD.sh were previously created by me in order to unmount a permanently-connected external USB HDD when a user logs out, to avoid an access problem when another user logs in (see an earlier blog post).

user $ cat /etc/lightdm/lightdm.conf.d/10_lubuntu.conf
[Seat:*]
session-cleanup-script=/etc/lightdm/lightdm.conf.d/unmount_FREECOM_HDD.sh

2. Modifications to enable installation to suspend when no user is logged in

2.1 Specify the scripts

user $ cd /etc/lightdm/lightdm.conf.d/
user $ sudo nano 10_lubuntu.conf
user $ cat 10_lubuntu.conf 
[Seat:*]
greeter-setup-script =/etc/lightdm/lightdm.conf.d/lightdm_sleep.sh
session-setup-script=/etc/lightdm/lightdm.conf.d/lightdm_kill_sleep.sh
session-cleanup-script=/etc/lightdm/lightdm.conf.d/unmount_FREECOM_HDD.sh

2.2 Create the two scripts

user $ sudo nano lightdm_sleep.sh
user $ sudo chmod +x lightdm_sleep.sh
user $ cat lightdm_sleep.sh 
#!/bin/sh
file="/tmp/unique_identifier"
(while true; do sleep 30m; systemctl suspend; done) &
echo $! > $file
user $ sudo nano lightdm_kill_sleep.sh
user $ sudo chmod +x lightdm_kill_sleep.sh
user $ cat lightdm_kill_sleep.sh 
#!/bin/sh
file="/tmp/unique_identifier"
if [ -f "$file" ]
then
    kill `cat $file`
    rm $file
fi

2.3 Modify the existing session cleanup script to include the lightdm_kill_sleep.sh code

user $ tail -n 11 unmount_FREECOM_HDD.sh
################################################
# Code below copied from lightdm_kill_sleep.sh
file="/tmp/unique_identifier"
if [ -f "$file" ]
then
    kill `cat $file`
    rm $file
fi
# End of code copied from lightdm_kill_sleep.sh
################################################
exit 0

Of course, specifying lightdm_kill_sleep.sh would have sufficed if the installation did not already have a session cleanup script:

user $ cat 10_lubuntu.conf
[Seat:*]
greeter-setup-script =/etc/lightdm/lightdm.conf.d/lightdm_sleep.sh
session-setup-script=/etc/lightdm/lightdm.conf.d/lightdm_kill_sleep.sh
session-cleanup-script=/etc/lightdm/lightdm.conf.d/lightdm_kill_sleep.sh

3. Summary
Thus the file situation is now as follows:

user $ ls /etc/lightdm/lightdm.conf.d/
05_lubuntu.conf  10_lubuntu.conf  lightdm_kill_sleep.sh  lightdm_sleep.sh  unmount_FREECOM_HDD.sh
  • If nobody logs in after booting the machine, the machine will suspend to RAM after 30 minutes* due to greeter-setup-script.
  • If a user logs in, session-setup-script ensures only Xfce Power Manager controls suspension to RAM while the LightDM greeter screen is not displayed.
  • If a user logs out and no other user is logged in, the machine will suspend to RAM after 30 minutes* due to greeter-setup-script.
  • If a user locks the screen, the machine will suspend to RAM after 30 minutes* due to greeter-setup-script.

*Obviously the period of inactivity to trigger suspension to RAM can be configured by changing the time specified in the lightdm_sleep.sh script.

HEIC image files in Linux

I was at an event recently where the attendees were asked to upload their camera and smartphone photos and videos to a shared Google Drive folder. Some of the uploaded photo files have a .HEIC (High Efficiency Image Container) extension, which I had not come across before. I have since learnt that these HEIC files were produced by iPhones running iOS 11, encoded using the HEIF (High Efficiency Image File) format. Apparently the HEIF format is superior to the JPEG format in a number of ways (see the links at the end of my post, especially the image examples given by Nokia), although it is subject to patents and therefore I believe there are certain constraints to coding image files in HEIC format. Anyway, I’ll leave you to read the fine print. My interest was simply because I wanted to be able to download the above-mentioned photo files and view them all in the file managers and image-viewing applications in Linux and Android on my various devices.

Now, I can browse and view the above-mentioned shared HEIC images in Google Drive in the Firefox and Chrome browsers in Linux, although an ownCloud site viewed using the same browsers displays the HEIC files as grey icons that can only be downloaded, not opened and viewed in the browser. I also found that Cirrus, the Android app for ownCloud that I use on my Galaxy Note 8 phone, cannot display HEIC photos either.

I downloaded the HEIC files to a machine running Lubuntu 18.04 and to a machine running Gentoo Linux. The file manager PCManFM in Lubuntu 18.04 displays grey icons rather than thumbnails for these HEIC files, and KDE’s Dolphin 18.08.3 file manager in Gentoo Linux displays green image icons rather than thumbnails for them. As far as Linux image viewers go, in Lubuntu 18.04 I find that GPicView 0.2.5 and Geeqie 1.4 cannot display HEIC images, and in Gentoo Linux KDE I find that GQview 2.1.5-r1, Okular 18.08.3 and Gwenview 18.08.3 cannot display HEIC images. So I set about converting all the HEIC files to JPG files. I managed to do this but needed to use a range of tools, as illustrated by a couple of examples below for Lubuntu 18.04 and Gentoo Linux. This post might seem long-winded but perhaps may be of help to Linux users coming across .HEIC files for the first time.

From the .HEIC files I had downloaded I picked one at random to try and convert to a JPG file: IMG_3706.HEIC. Its EXIF data confirms it is an HEIC file:

user $ exiftool IMG_3706.HEIC | grep "File Type"
File Type                       : HEIC
File Type Extension             : heic
user $ exiftool IMG_3706.HEIC | grep "Camera Model"
Camera Model Name               : iPhone 7 Plus

Several of the files with the .HEIC suffix that I downloaded were not real HEIC files according to their EXIF data:

user $ exiftool IMG_9474.HEIC | grep "File Type"
File Type                       : JPEG
File Type Extension             : jpg
user $ exiftool IMG_9474.HEIC | grep "Camera Model"
Camera Model Name               : iPhone 8

Those files were apparently treated as JPEG files by the tools I mention below, so I have omitted the results for those ‘false’ HEIC files.

Lubuntu 18.04

1. I installed the libheif example tools:

user $ sudo apt install libheif-examples

2. I used the heif-info command to check the file:

user $ heif-info IMG_3706.HEIC 
image: 3024x4032 (id=49), primary
  thumbnail: 240x320
  alpha channel: no
  depth channel: no

3. I tried to convert the file using the heif-convert command:

user $ heif-convert IMG_3706.HEIC IMG_3706.jpg
File contains 1 images
Written to IMG_3706.jpg

4. Apparently Imagemagick >=7.0.7-22 compiled with --with-libheif is supposed to be able to convert HEIC files to JPG. Anyway, I tried to convert the file using the current version of Imagemagick in Lubuntu 18.04 (the current package version is 8:6.9.7.4+dfsg-16ubuntu6.4):

user $ convert IMG_3706.HEIC IMG_3706a.jpg
convert-im6.q16: no decode delegate for this image format `HEIC' @ error/constitute.c/ReadImage/504.
convert-im6.q16: no images defined `IMG_3706a.jpg' @ error/convert.c/ConvertImageCommand/3258.

5. Apparently the GIMP >=2.10.2 supports HEIF by using heif-gimp-plugin. Anyway, I tried to open the file with the current version of the GIMP in Lubuntu 18.04 (the current package version is 2.8.22-1). The GIMP launches and pops-up a window with the title ‘GIMP Message’ containing the following message and an ‘OK’ button:

GIMP Message
Opening /home/fitzcarraldo/IMG_3706.HEIC’ failed: Unknown file type

6. I used the online tool ‘libheif decoder demo’ (https://strukturag.github.io/libheif/) in a browser window. This can load the file IMG_3706.HEIC (‘Browse…’ button) and convert it (‘Save image…’ button) to IMG_3706.jpeg.

Gentoo Linux with KDE 5

1. I installed the libheif example tools implicitly by re-merging Imagemagick with USE="heif", which installs libheif.

root # cat /etc/portage/package.use/imagemagick 
media-gfx/imagemagick heif
root # emerge imagemagick

2. I used the heif-info command to check the file:

user $ heif-info IMG_3706.HEIC  
image: 3024x4032 (id=49), primary
  thumbnail: 240x320
  alpha channel: no
  depth channel: no

3. I tried to convert the file using the heif-convert command:

user $ heif-convert IMG_3706.HEIC IMG_3706.jpg
File contains 1 images
Written to IMG_3706.jpg

4. I tried to convert the file using Imagemagick >=7.0.7-22 compiled with --with-libheif (Imagemagick merged with USE="heif"):

user $ convert IMG_3706.HEIC IMG_3706a.jpg
user $

So Imagemagick 7.0.8.16 in Gentoo has no trouble with the file IMG_3706.HEIC.

5. I tried to open the file with the GIMP >=2.10.2, which supports HEIF using heif-gimp-plugin (GIMP >=2.10.6-r1 with USE="heif" in the case of Gentoo Linux)

First I re-merged the GIMP with the heif USE flag:

root # cat /etc/portage/package.accept_keywords/gimp
=media-gfx/gimp-2.10.8-r1 ~amd64
# required by media-gfx/gimp-2.10.8-r1::gentoo
=media-libs/libmypaint-1.3.0 ~amd64
# required by media-gfx/gimp-2.10.8-r1::gentoo
=media-gfx/mypaint-brushes-1.3.0-r1 ~amd64
# required by media-gfx/gimp-2.10.8-r1::gentoo
=media-libs/gegl-0.4.12 ~amd64
# required by media-gfx/gimp-2.10.8-r1::gentoo
=media-libs/babl-0.1.60 ~amd64
root # cat /etc/portage/package.use/gimp
media-gfx/gimp heif
root # emerge -1vp gimp

These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild  N    ~] media-gfx/mypaint-brushes-1.3.0-r1:1.0::gentoo  2,390 KiB
[ebuild     U ~] media-libs/babl-0.1.60::gentoo [0.1.38::gentoo] USE="(-altivec)" CPU_FLAGS_X86="mmx sse sse2 sse3%* sse4_1 -f16c" 670 KiB
[ebuild  N     ] media-libs/gexiv2-0.10.8::gentoo  USE="-introspection -python -static-libs -test -vala" PYTHON_TARGETS="python2_7 python3_6 -python3_4 -python3_5" 620 KiB
[ebuild  NS   ~] media-libs/gegl-0.4.12:0.4::gentoo [0.2.0-r5:0::gentoo] USE="cairo ffmpeg introspection lcms openexr sdl svg tiff v4l -debug -jpeg2k -lensfun -libav -raw -test -umfpack -vala -webp" CPU_FLAGS_X86="mmx sse" 6,900 KiB
[ebuild  NS    ] media-libs/gegl-0.3.26:0.3::gentoo [0.2.0-r5:0::gentoo] USE="cairo ffmpeg introspection lcms openexr sdl svg tiff v4l -debug -jpeg2k -lensfun -raw -test -umfpack -vala -webp" CPU_FLAGS_X86="mmx sse" 6,378 KiB
[ebuild  N    ~] media-libs/libmypaint-1.3.0::gentoo  USE="gegl nls openmp -introspection" 428 KiB
[ebuild     U ~] media-gfx/gimp-2.10.8-r1:2::gentoo [2.8.22-r1:2::gentoo] USE="alsa heif%* mng openexr%* udev wmf -aalib (-altivec) (-aqua) -debug -doc -gnome -jpeg2k -postscript -python -smp -test -unwind% -vector-icons% -webp% -xpm (-bzip2%*) (-curl%) (-dbus%*) (-exif%*) (-jpeg%*) (-lcms%*) (-pdf%*) (-png%*) (-svg%*) (-tiff%*)" CPU_FLAGS_X86="mmx sse" PYTHON_TARGETS="python2_7" 31,206 KiB

Total: 7 packages (2 upgrades, 3 new, 2 in new slots), Size of downloads: 48,591 KiB

I then launched the GIMP and successfully opened the file IMG_3706.HEIC, and I was able to export it as IMG_3706.jpg.

6. As would be expected, the online tool ‘libheif decoder demo’ (https://strukturag.github.io/libheif/) behaves exactly the same in Gentoo Linux as it does in Lubuntu 18.04 (see earlier).

Summary

So there you have it; if the Linux file manager and/or image viewing applications you use cannot already handle HEIC files, the tools in Linux that I found may work are as follows:

  • heif-convert (from the package libheif-examples in Ubuntu/Lubuntu, or from from the package libheif in Gentoo).
  • Imagemagick (not every version).
  • The GIMP (not every version).
  • the online tool ‘libheif decoder demo’ (https://strukturag.github.io/libheif/).

I have not tried the copyright open-source code from Nokia (see link under Further Reading below), qt-heif-image-plugin and tifig (not in active development). If you have had success using another tool to convert HEIC files, please post a comment below for the benefit of other users, giving the name of the tool, the package name and version, and the Linux distribution (including release number, if not a rolling distribution).

Further reading

  1. Wikipedia – High Efficiency Image File Format
  2. Lifewire – What Are HEIF and HEIC, and Why Is Apple Using Them?
  3. Nokia – High Efficiency Image File Format (HEIF)
  4. libheif – a ISO/IEC 23008-12:2017 HEIF file format decoder and encoder
  5. askubuntu – Any app on Ubuntu to open HEIF (.heic, High Efficiency Image File Format) pictures?

How to display the times in various time zones from the LXDE Panel

I normally check the time in the time zone of family, friends and colleagues who live in various places around the World before I call or message them. In KDE Plasma on my laptop it is possible to configure the digital clock widget to display the times in a list of time zones of my choice when I hover the mouse pointer over the widget. However, my family’s PC has Lubuntu 18.04 installed, which uses LXDE, and the digital clock on the LXDE Panel does not have that ability. Therefore I installed the GUI utility gworldclock in Lubuntu 18.04:

$ sudo apt-get install gworldclock

I added it to the ‘Application Launch and Task Bar’ plugin on the LXDE Panel, and a clock icon is now displayed on the Panel.

gworldclock icon on Application Launch and Task Bar on LXDE Panel

gworldclock icon on Application Launch and Task Bar on LXDE Panel

When I click the clock icon, a window opens on the Desktop and displays the date and time at each of the World locations I configured in gworldclock (‘Options’ > ‘Add Timezone’). Excellent, and almost as convenient as the World time feature in the Digital Clock widget in KDE Plasma 5.

gworldclock window default size

gworldclock window default size

I have configured gworldclock to display a list of ten additional time zones when I click on the clock icon on the Application Launch and Task Bar on the Panel. However, the size of the pop-up gworldclock window was relatively small; only six of the eleven time zones were visible, so I had to use the window’s scroll bar in order to view some of the configured time zone entries. I therefore made some changes in LXDE in order to display a larger gworldclock window showing all eleven time zones. This is how I did it.

1. I installed wmctrl:

$ sudo apt-get install wmctrl

2. I created a hidden Bash script ~/.gworldclockfitzcarraldo.sh containing the following:

#!/bin/bash
gworldclock &
sleep 0.5s
wmctrl -F gworldclock -r gworldclock -e 0,500,300,300,340

and made it executable:

$ chmod +x ~/.gworldclockfitzcarraldo.sh

See man wmctrl for the meaning of the options in the above-mentioned Bash script.

3. I created the Desktop Configuration File ~/.local/share/applications/gworldclockfitzcarraldo.desktop containing the following:

[Desktop Entry]
Comment=See the time in other timezones
Name=gworldclock
GenericName=World Clock
Encoding=UTF-8
Comment[fr]=Voir l'heure dans d'autres fuseaux horaires
Exec=/home/fitzcarraldo/.gworldclockfitzcarraldo.sh
Terminal=false
Type=Application
Icon=gworldclock
Categories=Utility;Clock;HamRadio

4. I edited the file ~/.config/lxpanel/Lubuntu/panels/panel and added an entry for the new Desktop Configuration File to the end of list for the Application Launch and Task Bar, as shown in the following excerpt from the file:

Plugin {
  type=launchtaskbar
  Config {
    Button {
      id=pcmanfm.desktop
    }
    Button {
      id=firefox.desktop
    }
    Button {
      id=google-chrome.desktop
    }
    Button {
      id=gedit.desktop
    }
    Button {
      id=lxterminal.desktop
    }
    Button {
      id=galculator.desktop
    }
    Button {
      id=gworldclockfitzcarraldo.desktop
    }
  }
}

Then I logged out and back in again. Now, when I click on the clock icon on the Panel, the gworldclock window opens at the location and size specified by the wmctrl command in the Bash script I created.

gworldclock window resized by the Bash script

gworldclock window resized by the Bash script

Configuring Lubuntu 18.04 to enable hibernation using a swap file

In an earlier post about Lubuntu 18.04 I stated that hibernation is precluded because the Lubuntu Installer installs the OS with a swap file instead of a swap partition. In fact, even with a swap file it is possible to configure Lubuntu so that hibernation is possible. This is how I did it.

1.  This PC has 4 GiB RAM but the Lubuntu Installer had created a 2 GiB swap file named /swapfile, so I increased the size of the swap file to 4 GiB to ensure it was large enough to store the memory image:

user $ sudo swapoff -a
user $ sudo dd if=/dev/zero of=/swapfile bs=1024 count=4M
user $ sudo chmod 600 /swapfile
user $ sudo mkswap /swapfile
user $ sudo swapoff -a
user $ sudo swapon /swapfile
user $ cat /proc/meminfo | grep -i memtotal
MemTotal:        3924108 kB
user $ ls -la /swapfile
-rw------- 1 root root 4294967296 Jul 10 18:25 /swapfile

Note that you can check the status of the swap file before and after the above steps by using either of the following commands:

user $ swapon -s
user $ free -m

2.  The Lubuntu Installer had previously configured /etc/fstab for the swap file, so I left that as it is:

user $ grep swapfile /etc/fstab
/swapfile                                 none            swap    sw              0       0

3.  I checked on which device the root partition with the file /swapfile is located (sda2 in my case) and found out its UUID (ignore the PARTUUID):

user $ sudo blkid
[sudo] password for fitzcarraldo:
/dev/sda1: UUID="3602-BD57" TYPE="vfat" PARTLABEL="EFI System Partition" PARTUUID="72b3693e-b81f-7299-84fb-bf3781bef43d"
/dev/sda2: UUID="afe17116-26fa-4169-b2d9-fb6ac8afc63c" TYPE="ext4" PARTUUID="738fed17-293d-832f-c7a4-e83471fe8ca6"

4.  I found the resume_offset for the file /swapfile, which is 16746496 in my case (look for the first value in the two columns under ‘physical_offset‘):

user $ sudo filefrag -v /swapfile
Filesystem type is: ef53
File size of /swapfile is 4294967296 (1048576 blocks of 4096 bytes)
 ext:     logical_offset:        physical_offset: length:   expected: flags:
   0:        0..   30719:   16746496..  16777215:  30720:            
   1:    30720..   63487:   16809984..  16842751:  32768:   16777216:
   2:    63488..   96255:   16842752..  16875519:  32768:            
   3:    96256..  126975:   16875520..  16906239:  30720:            
   4:   126976..  129023:   16908288..  16910335:   2048:   16906240:
   5:   129024..  161791:   16912384..  16945151:  32768:   16910336:
   6:   161792..  194559:   16945152..  16977919:  32768:            
   7:   194560..  227327:   16977920..  17010687:  32768:            
   8:   227328..  249855:   17010688..  17033215:  22528:            
   9:   249856..  282623:   17035264..  17068031:  32768:   17033216:
  10:   282624..  315391:   17068032..  17100799:  32768:            
  11:   315392..  319487:   17100800..  17104895:   4096:            
  12:   319488..  321535:   17121280..  17123327:   2048:   17104896:
  13:   321536..  325631:   17129472..  17133567:   4096:   17123328:
  14:   325632..  327679:   17137664..  17139711:   2048:   17133568:
  15:   327680..  329727:   17143808..  17145855:   2048:   17139712:
  16:   329728..  331775:   17154048..  17156095:   2048:   17145856:
  17:   331776..  339967:   17162240..  17170431:   8192:   17156096:
  18:   339968..  344063:   24485888..  24489983:   4096:   17170432:
  19:   344064..  346111:   32665600..  32667647:   2048:   24489984:
  20:   346112..  348159:   32677888..  32679935:   2048:   32667648:
  21:   348160..  350207:   33261568..  33263615:   2048:   32679936:
  22:   350208..  352255:   33363968..  33366015:   2048:   33263616:
  23:   352256..  354303:   33853440..  33855487:   2048:   33366016:
  24:   354304..  356351:   34000896..  34002943:   2048:   33855488:
  25:   356352..  389119:   34027520..  34060287:  32768:   34002944:
  26:   389120..  391167:   34060288..  34062335:   2048:            
  27:   391168..  393215:   34134016..  34136063:   2048:   34062336:
  28:   393216..  395263:   34158592..  34160639:   2048:   34136064:
  29:   395264..  428031:   34189312..  34222079:  32768:   34160640:
  30:   428032..  452607:   34222080..  34246655:  24576:            
  31:   452608..  485375:   34248704..  34281471:  32768:   34246656:
  32:   485376..  518143:   34281472..  34314239:  32768:            
  33:   518144..  550911:   34314240..  34347007:  32768:            
  34:   550912..  583679:   34347008..  34379775:  32768:            
  35:   583680..  616447:   34379776..  34412543:  32768:            
  36:   616448..  643071:   34412544..  34439167:  26624:            
  37:   643072..  645119:   34445312..  34447359:   2048:   34439168:
  38:   645120..  649215:   34457600..  34461695:   4096:   34447360:
  39:   649216..  659455:   34463744..  34473983:  10240:   34461696:
  40:   659456..  688127:   34476032..  34504703:  28672:   34473984:
  41:   688128..  690175:   34506752..  34508799:   2048:   34504704:
  42:   690176..  692223:   34510848..  34512895:   2048:   34508800:
  43:   692224..  724991:   34514944..  34547711:  32768:   34512896:
  44:   724992..  757759:   34549760..  34582527:  32768:   34547712:
  45:   757760..  778239:   34582528..  34603007:  20480:            
  46:   778240..  786431:   34637824..  34646015:   8192:   34603008:
  47:   786432..  819199:   34648064..  34680831:  32768:   34646016:
  48:   819200..  843775:   34680832..  34705407:  24576:            
  49:   843776..  845823:   34707456..  34709503:   2048:   34705408:
  50:   845824..  849919:   34713600..  34717695:   4096:   34709504:
  51:   849920..  854015:   34729984..  34734079:   4096:   34717696:
  52:   854016..  886783:   34744320..  34777087:  32768:   34734080:
  53:   886784..  919551:   34777088..  34809855:  32768:            
  54:   919552..  950271:   34809856..  34840575:  30720:            
  55:   950272..  983039:   34842624..  34875391:  32768:   34840576:
  56:   983040.. 1015807:   34875392..  34908159:  32768:            
  57:  1015808.. 1048575:   34908160..  34940927:  32768:             last,eof
/swapfile: 38 extents found

Note that you can also find the resume_offset by installing the package uswsusp and using the command swap-offset on the swap file:

user $ sudo apt install uswsusp
user $ sudo swap-offset /swapfile
resume offset = 16746496

5.  I updated the file /boot/grub/grub.cfg using the information found in Steps 3 & 4 as follows:

5.1  I added ‘resume=UUID=afe17116-26fa-4169-b2d9-fb6ac8afc63c resume_offset=16746496 resumedelay=15‘ to the parameters in the variable GRUB_CMDLINE_LINUX_DEFAULT in the file /etc/default/grub (Your existing parameters could be different to mine; that is not a problem):

user $ sudo nano /etc/default/grub
#
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor acpi_osi='!Windows 2013' acpi_osi='!Windows 2012' resume=UUID=afe17116-26fa-4169-b2d9-fb6ac8afc63c resume_offset=16746496 resumedelay=15"
#

Note that the optional ‘resumedelay=15‘ specifies the delay (in seconds) to pause before attempting to read the resume files. I added this to try to allow enough time for the filesystem containing the swap file to become Read-Write.

5.2  I regenerated /boot/grub/grub.cfg by using the following command:

user $ sudo update-grub

6.  I edited the file /etc/initramfs-tools/conf.d/resume using the information found in Steps 3 & 4, and regenerated the initramfs files for the kernel images in the /boot directory:

user $ sudo nano /etc/initramfs-tools/conf.d/resume
RESUME=UUID=afe17116-26fa-4169-b2d9-fb6ac8afc63c resume_offset=16746496
# Resume from /swapfile
user $ sudo update-initramfs -u -k all

7.  I edited the Polkit rules files to permit hibernation (Create the files if they do not already exist):

7.1  For Polkit version 0.106 and higher

user $ sudo nano /etc/polkit-1/rules.d/85-suspend.rules
polkit.addRule(function(action, subject) {
    if (action.id == "org.freedesktop.login1.suspend" ||
        action.id == "org.freedesktop.login1.suspend-multiple-sessions" ||
        action.id == "org.freedesktop.login1.hibernate" ||
        action.id == "org.freedesktop.login1.hibernate-multiple-sessions")
    {
        return polkit.Result.YES;
    }
});

7.2  For Polkit versions below 0.106

user $ sudo nano /var/lib/polkit-1/localauthority/50-local.d/50-enable-suspend-on-lockscreen.pkla
[Allow hibernation and suspending with lock screen]
Identity=unix-user:*
Action=org.freedesktop.login1.suspend;org.freedesktop.login1.suspend-multiple-sessions;org.freedesktop.login1.hibernate;org.freedesktop.login1.hibernate-multiple-sessions
ResultAny=yes
ResultInactive=yes
ResultActive=yes

It does not do any harm to create both the above-mentioned rules files, whatever the version of Polkit that happens to be installed.

8.  I rebooted, logged in, launched a few GUI applications and then clicked on the Lubuntu menu icon on the Panel and selected ‘Logout’ > ‘Hibernate’, which did put the machine into hibernation. I then pressed the PC’s power push-button to resume from disk, entered my password on the lock screen and the Desktop appeared exactly as it was prior to hibernation. All good.

Getting the lock screen to work reliably when resuming from suspension in a single-seat, multi-user Lubuntu 18.04 installation

In an earlier post I described my attempt at getting the lock screen to work reliably in the single-seat, multi-user Lubuntu 17.10 installation on my family’s desktop PC. Although the modifications described in that post seemed to improve matters somewhat, users were still not always able to login from the LightDM greeter screen after resuming from Suspend to RAM in the following situation:

  1. User_A logs in to User_A’s account but does not log out after using the account.
  2. User_B clicks on ‘Logout’ > ‘Switch User’ to log in to User_B’s account but does not log out.
  3. User_A clicks on ‘Logout’ > ‘Switch User’ to get back to User_A’s account.
  4. User_A allows his/her session to timeout and suspend to RAM.
  5. User_B presses a key on the keyboard to resume from suspension, and the LightDM lock screen is displayed.
  6. User_B enters his/her password and then clicks on ‘Unlock’, but the LightDM lock screen remains on display and nobody can log in any more, although the keys on the lock screen are still clickable.

When this occurs, the only way users can access their Desktop is to click on the Power icon in the top right corner of the lock screen and select ‘Restart…’.

The Software Updater in Lubuntu 17.10 recently offered me the choice of upgrading to Lubuntu 18.04, which I accepted. The upgrade was performed and the only hitch that resulted was an incorrect initramfs, which was simple enough to fix (see my post Lubuntu 18.04 ‘Gave up waiting for suspend/resume device’). However, the above-mentioned problem of unlocking after resuming from suspension still occurred in Lubuntu 18.04. Below are the changes I made since the modifications described in my post Getting the lock screen to work properly when resuming from Suspend-to-RAM with multiple sessions in Lubuntu 17.10 (the other changes in that post remain), which seem to have cured the problem.

Change to Item 2 in my earlier post

I reverted the Exec line in /etc/xdg/autostart/light-locker.desktop back to how it was originally following installation of Lubuntu:

user $ grep Exec /etc/xdg/autostart/light-locker.desktop
Exec=light-locker

Change to Item 3 in my earlier post

I deleted the file /lib/systemd/system-sleep/hang-fix that I had previously created:

user $ sudo rm /lib/systemd/system-sleep/hang-fix

Change to Item 7 in my earlier post

The Xfce Power Manager ‘Security’ tab for each user now has ‘Lock screen when system is going for sleep’ ticked:

Light Locker

  • Automatically lock the session: Never
  • Delay locking after screensaver for: ‘1 Seconds’ is greyed out
  • ‘Lock screen when system is going for sleep’ is ticked

The full Xfce Power Manager settings for each user (see the file ~/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-power-manager.xml in each user’s home directory) are now configured as follows:

<?xml version="1.0" encoding="UTF-8"?>

<channel name="xfce4-power-manager" version="1.0">
  <property name="xfce4-power-manager" type="empty">
    <property name="power-button-action" type="empty"/>
    <property name="show-tray-icon" type="empty"/>
    <property name="brightness-switch-restore-on-exit" type="int" value="1"/>
    <property name="brightness-switch" type="int" value="0"/>
    <property name="presentation-mode" type="bool" value="false"/>
    <property name="inactivity-on-ac" type="uint" value="30"/>
    <property name="blank-on-ac" type="int" value="10"/>
    <property name="dpms-on-ac-sleep" type="uint" value="0"/>
    <property name="dpms-on-ac-off" type="uint" value="0"/>
    <property name="brightness-on-ac" type="uint" value="9"/>
    <property name="lock-screen-suspend-hibernate" type="bool" value="true"/>
    <property name="logind-handle-lid-switch" type="bool" value="false"/>
    <property name="dpms-enabled" type="bool" value="false"/>
    <property name="general-notification" type="bool" value="true"/>
  </property>
</channel>

Additional modifications

In another of my posts (Prevent Lubuntu 17.10 from leaving an external HDD mounted incorrectly for other users) I explained the modifications I made in Lubuntu 17.10 for a single-seat, multi-user installation to work properly with a permanently connected external USB HDD. However, I recently noticed the following problems resulting from those modifications:

A. The following error message in the LightDM log file /var/log/lightdm/lightdm.log:

[SeatDefaults] is now called [Seat:*], please update this configuration

So I changed the contents of the file /etc/lightdm/lightdm.conf.d/10_lubuntu.conf from:

[SeatDefaults]
session-cleanup-script=/etc/lightdm/lightdm.conf.d/unmount_FREECOM_HDD.sh

to:

[Seat:*]
session-cleanup-script=/etc/lightdm/lightdm.conf.d/unmount_FREECOM_HDD.sh

B. The following error message in the LightDM log file/var/log/lightdm/lightdm.log when the USB external HDD happened to not be mounted at the time:

DEBUG: Launching process 8569: /etc/lightdm/lightdm.conf.d/unmount_FREECOM_HDD.sh
DEBUG: Process 8569 terminated with signal 11

So I changed the contents of my Bash script /etc/lightdm/lightdm.conf.d/unmount_FREECOM_HDD.sh from:

#!/bin/bash
udisksctl unmount --block-device /dev/disk/by-uuid/C6576A087368B015

to:

#!/bin/bash
STATUS=`mount | grep $(readlink -f /dev/disk/by-uuid/C6576A087368B015 )`
if [[ ! -z $STATUS ]]; then
    udisksctl unmount --block-device /dev/disk/by-uuid/C6576A087368B015
fi
exit 0

Conclusions

It is early days, but so far the login problem for other users after resuming from suspension has not reoccurred since I made the latest changes. I am not sure if the modifications described in my post ‘Prevent Lubuntu 17.10 from leaving an external HDD mounted incorrectly for other users‘ contributed to (or caused) the login problem, or whether one or more of systemd-logind, LightDM, LightDM GTK+ Greeter, Light Locker and Xfce Power Manager are to blame (since they have to work holistically to provide the required functionality). It is frustrating not knowing the root cause of the problem, but at least my family no longer has to worry about being able to log in if a family member has not logged out and left the PC to suspend.

Lubuntu 18.04 ‘Gave up waiting for suspend/resume device’

Software Updater in Lubuntu 17.10 recently prompted me to upgrade the OS to 18.04 LTS, and I clicked on ‘Yes, Upgrade Now’. The upgrade was performed and I was able to boot the PC into 18.04, login and access the Desktop as usual. However, I noticed a new message ‘Gave up waiting for suspend/resume device‘ was displayed on TTY1.

Now, I recalled that the Lubuntu 17.10 Installer had created a swap file rather than a swap partition when I installed Lubuntu, as confirmed in the output listed below:

user $ sudo blkid
[sudo] password for fitzcarraldo: 
/dev/sda1: UUID="3602-BD57" TYPE="vfat" PARTLABEL="EFI System Partition" PARTUUID="72b3693e-b81f-7299-84fb-bf3781bef43d"
/dev/sda2: UUID="afe17116-26fa-4169-b2d9-fb6ac8afc63c" TYPE="ext4" PARTUUID="738fed17-293d-832f-c7a4-e83471fe8ca6"
user $ swapon
NAME      TYPE SIZE USED PRIO
/swapfile file   2G   0B   -2
user $ ls /swapfile 
/swapfile

The initramfs installed by upgrading to Lubuntu 18.04 expects a swap partition in order to resume from hibernation:

user $ lsinitramfs /initrd.img | grep resume
scripts/local-premount/resume
bin/resume
conf/conf.d/resume

And, when I regenerated the initramfs files for the three kernel images in the /boot directory, I could see from the terminal output that the update-initramfs tool was expecting a swap partition:

user $ sudo update-initramfs -u -k all
update-initramfs: Generating /boot/initrd.img-4.15.0-23-generic
W: initramfs-tools configuration sets RESUME=UUID=7b4cb3c5-4c17-42ae-be3c-cc35d31fe287
W: but no matching swap device is available.
update-initramfs: Generating /boot/initrd.img-4.15.0-22-generic
W: initramfs-tools configuration sets RESUME=UUID=7b4cb3c5-4c17-42ae-be3c-cc35d31fe287
W: but no matching swap device is available.
update-initramfs: Generating /boot/initrd.img-4.13.0-43-generic
W: initramfs-tools configuration sets RESUME=UUID=7b4cb3c5-4c17-42ae-be3c-cc35d31fe287
W: but no matching swap device is available.

I had a look in the file /etc/initramfs-tools/conf.d/resume and found that it had indeed been configured to expect a swap partition, although I have no idea where that UUID came from, as it was not for any of the partitions on this PC:

user $ cat /etc/initramfs-tools/conf.d/resume
RESUME=UUID=7b4cb3c5-4c17-42ae-be3c-cc35d31fe287

So I edited the contents of the configuration file to point to the swap file /swapfile instead of a non-existent partition:

user $ cat /etc/initramfs-tools/conf.d/resume
#RESUME=UUID=7b4cb3c5-4c17-42ae-be3c-cc35d31fe287
RESUME=/swapfile

Then I regenerated the initramfs files for the three kernel images currently in /boot on the PC:

user $ sudo update-initramfs -u -k all
update-initramfs: Generating /boot/initrd.img-4.15.0-23-generic
update-initramfs: Generating /boot/initrd.img-4.15.0-22-generic
update-initramfs: Generating /boot/initrd.img-4.13.0-43-generic

As you can see above, there were no longer any messages that ‘no matching swap device is available‘. And, when I rebooted the PC, the message ‘Gave up waiting for suspend/resume device‘ was no longer displayed on TTY1. All good again, although it’s a pity the Lubuntu Installer did not create a swap partition so that the installation could be put into hibernation. With a swap file, hibernation is not possible.

Update (14 July 2018): Actually, it is possible to hibernate if the installation has a swap file instead of a swap partition – see my latest post: Configuring Lubuntu 18.04 to enable hibernation using a swap file.

Getting the lock screen to work properly when resuming from Suspend-to-RAM with multiple sessions in Lubuntu 17.10

Introduction

What is it with Linux and lock screens?! There are umpteen posts on the Web by Linux users having trouble with lock screens, particularly the LightDM session locker Light Locker. Well, here is my contribution.

Lubuntu 17.10 is installed on my family’s desktop PC (single seat, multiple users). Lubuntu 17.10 uses systemd-logind, LightDM, Light Locker and Xfce Power Manager, and they do not work properly holistically in my experience. To confuse matters further, Lubuntu 17.10 also has XScreenSaver installed, which also has lock-screen capabilities.

In Lubuntu 17.10 on my family’s desktop PC, Light Locker displays the LightDM GTK+ Greeter screen when anyone wakes/resumes the PC from suspension by pressing a key on the USB keyboard, and users should then be able to log in by selecting their username from the pull-down list on the LightDM GTK+ Greeter screen and entering their password. However, if only a single user session existed when the PC suspended automatically (i.e. by timeout), upon resuming from suspension a black screen with a white padlock icon and the following message in white/grey text from light-locker would appear:

This session is locked
You’ll be redirected to the unlock
dialog automatically in a few seconds

But then nothing else happened; the above-mentioned message remained on display. I could press Ctrl+Alt+F1, login on TTY1 and enter the command ‘loginctl unlock-sessions‘ to get back to the Desktop, but that is not something the rest of my family would know how to do or be comfortable doing. In any case, I have only given sudo rights to one other member of the family.

Another problem would occur if the PC was left to suspend automatically with more than one user still logged in (i.e. more than one session). Although Light Locker would display the LightDM GTK+ Greeter screen upon resuming from suspension, and users could select their username from the pull-down list and enter their password, the LightDM GTK+ Greeter screen would remain on display and it would no longer be possible to re-enter a password (although it was still possible to select users from the pull-down list of users, and to select ‘Suspend’, ‘Restart…’ and ‘Shutdown…’ from the pull-down power menu). However, if users suspended the PC manually by selecting ‘Logout’ > ‘Lock Screen’ from the Lubuntu Menu, upon waking/resuming it was possible to enter their password on the LightDM GTK+ Greeter screen to return to their Desktop.

In this article I explain what I did to try and rectify these problems.

By the way, note that hibernation is disabled by default in Lubuntu 17.10 and you may need to make further changes if you want to enable hibernation as well. For example, does the PC have a swap partition, and is it large enough to enable hibernation? Also see the article: How to Enable Hibernate in Ubuntu 17.10 for possible help.

Modifications

The package light-locker-settings was not installed in Lubuntu 17.10. Do not install it. If it happens to be installed do not use ‘Preferences’ > ‘Light Locker Settings’, as it makes the Exec entry in the user’s light-locker.desktop file just ‘Exec=‘ or ‘Exec=light-locker‘. In fact, having installed light-locker-settings manually to check what could be configured via its GUI, I uninstalled it in order to stop anyone using it. (Under ‘Screensaver’, the Light Locker Settings GUI displays the following message: ‘Your screensaver settings are managed by Xfce Power Manager.’ and there is a button ‘Open’ to click on to launch the Xfce Power Manager settings GUI.) Presumably this was why it was not included when Lubuntu 17.10 was first installed to the HDD.

1.  I removed any light-locker.desktop files of individual users, leaving only the system-wide file:

$ sudo rm /home/*/.config/autostart/light-locker.desktop
$ sudo updatedb
$ locate light-locker.desktop
/etc/xdg/autostart/light-locker.desktop

2.  I edited the system-wide light-locker.desktop file to contain the following command to execute Light Locker:

$ grep Exec /etc/xdg/autostart/light-locker.desktop
Exec=light-locker --lock-after-screensaver=0 --no-lock-on-suspend --no-lock-on-lid --no-idle-hint

3.  I created the Bash script file /lib/systemd/system-sleep/hang-fix for systemd to run when suspending and resuming from suspension, with the permissions shown:

#!/bin/sh
case "$1" in
    pre|suspend|hibernate)
        date | tr -d '\n' >> /home/fitzcarraldo/sleep.log
        echo " going to sleep." >> /home/fitzcarraldo/sleep.log
        chvt 1
        loginctl unlock-sessions
    ;;
    post|resume|thaw)
        date | tr -d '\n' >> /home/fitzcarraldo/sleep.log
        echo " waking from sleep." >> /home/fitzcarraldo/sleep.log
        loginctl lock-sessions
        chvt 7
    ;;
    *)
        exit $NA
    ;;
esac
exit 0

$ sudo chmod 755 /lib/systemd/system-sleep/hang-fix
$ ls -la /lib/systemd/system-sleep/hang-fix
-rwxr-xr-x 1 root root 581 Apr 14 08:09 /lib/systemd/system-sleep/hang-fix

The above script is a hack to get around the problem of Light Locker resuming and apparently not knowing which session to unlock. I used the loginctl commands in this script rather than the Xfce Power Manager suspend options and Light Locker options such as ‘--late-locking‘ and ‘--lock-on-suspend‘ because I found that the Light Locker options and the Xfce Power Manager options did not fix the problem.

4.  I created two files for Polkit (to cover all Polkit versions to date) with the permissions as shown below.

4.1  The file /etc/polkit-1/rules.d/85-suspend.rules with the following contents:

polkit.addRule(function(action, subject) {
    if (action.id == "org.freedesktop.login1.suspend" ||
        action.id == "org.freedesktop.login1.suspend-multiple-sessions" ||
        action.id == "org.freedesktop.login1.hibernate" ||
        action.id == "org.freedesktop.login1.hibernate-multiple-sessions")
    {
        return polkit.Result.YES;
    }
});

If you do not have a swap partition large enough to enable hibernation, or you do not want to allow the PC to hibernate, use the following instead of the above:

polkit.addRule(function(action, subject) {
    if (action.id == "org.freedesktop.login1.suspend" ||
        action.id == "org.freedesktop.login1.suspend-multiple-sessions")
    {
        return polkit.Result.YES;
    }
});

$ sudo chmod 755 /etc/polkit-1/rules.d
$ sudo chmod 644 /etc/polkit-1/rules.d/85-suspend.rules
$ ls -la /etc/polkit-1/rules.d/85-suspend.rules
-rw-r--r-- 1 root root 359 Apr 19 22:14 /etc/polkit-1/rules.d/85-suspend.rules

4.2  The file /var/lib/polkit-1/localauthority/50-local.d/50-enable-suspend-on-lockscreen.pkla with the following contents:

[Allow suspending with lock screen]
Identity=unix-user:*
Action=org.freedesktop.login1.suspend;org.freedesktop.login1.suspend-multiple-sessions;org.freedesktop.login1.hibernate;org.freedesktop.login1.hibernate-multiple-sessions
ResultAny=yes
ResultInactive=yes
ResultActive=yes

If you do not have a swap partition large enough to enable hibernation, or you do not want to allow the PC to hibernate, use the following instead of the above:

[Allow suspending with lock screen]
Identity=unix-user:*
Action=org.freedesktop.login1.suspend;org.freedesktop.login1.suspend-multiple-sessions
ResultAny=yes
ResultInactive=yes
ResultActive=yes

$ sudo chmod 644 /var/lib/polkit-1/localauthority/50-local.d/50-enable-suspend-on-lockscreen.pkla
$ sudo ls -la /var/lib/polkit-1/localauthority/50-local.d/50-enable-suspend-on-lockscreen.pkla
-rw-r--r-- 1 root root 191 Apr 20 10:01 /var/lib/polkit-1/localauthority/50-local.d/50-enable-suspend-on-lockscreen.pkla

The above files are intended to get rid of the following error messages in a pop-up window and pop-up notification ballon, respectively, that prevent the OS from suspending automatically:

Authentication
Authentication is required for suspending
the system while other users are logged in.

Power Manager
GDBus.Error:org.freedesktop.DBus.Error.NoReply:
Method call timed out

By the way, the version of Polkit installed currently is 0.105:

$ pkaction --version
pkaction version 0.105

5.  I added all users to the users group (although I do not think this is essential):

$ sudo usermod -a -G users fitzcarraldo
$ sudo usermod -a -G users molly
$ sudo usermod -a -G users aquilino
$ sudo usermod -a -G users cholo
$ sudo usermod -a -G users paul

6.  I made sure the XScreenSaver settings for each user are as follows:

XScreenSaver (‘Preferences’ > ‘Screensaver’)

The ‘Display Modes’ tab has:

  • ‘Mode: Disable Screen Saver’

The ‘Advanced’ tab has everything unticked on it except for:

7.  I made sure the Xfce Power Manager settings for each user are as follows:

Xfce Power Manager (‘Preferences’ > ‘Power Manager’)

The ‘General’ tab has:
Buttons

  • When power button is pressed: Ask
  • When sleep button is pressed: Do nothing
  • When hibernate button is pressed: Do nothing

Appearance

  • Show notifications is ticked
  • Show system tray icon is ticked

The ‘System’ tab has:
System power saving

  • System sleep mode: Suspend
  • When inactive for 15 Minutes (You can make the number of minutes different for each user, if you want.)

The ‘Display’ tab has:
Display power management settings

  • ‘Handle display power management’ is ticked
  • Blank after: 5 Minutes
  • Put to sleep after: Never
  • Switch off after: Never

The ‘Security’ tab has:
Light Locker

  • Automatically lock the session: Never
  • Delay locking after screensaver for: ‘1 Seconds’ is greyed out
  • ‘Lock screen when system is going for sleep’ is not ticked

8.  I made sure the ‘Default Applications for LXSession’ settings for each user are as follows:

Select ‘Preferences’ > ‘Default Applications for LXSession’, click on ‘Autostart’ and untick ‘XScreenSaver’ if it is ticked. ‘Power Manager’ and ‘Screen Locker’ should already be ticked, so tick them if they are not. I left ‘PolicyKit Handler’ and ‘PolicyKit Authentication Agent’ unticked (Lubuntu 17.10 uses Polkit, the successor to PolicyKit).

9.  Although Lubuntu 17.10 does not use GNOME, I found that gsettings is installed. I did the following just in case, although I believe it is irrelevant in this particular case:

$ gsettings --version
2.54.1
$ gsettings set org.gnome.desktop.screensaver ubuntu-lock-on-suspend 'false'
$ gsettings get org.gnome.desktop.screensaver ubuntu-lock-on-suspend
false
$ gsettings set org.gnome.desktop.screensaver lock-enabled 'false'
$ gsettings get org.gnome.desktop.screensaver lock-enabled
false

Conclusion

After doing all the above, upon resuming from Suspend-to-RAM on most, but not all, occasions it is now possible to select any username on the LightDM GTK+ Greeter screen, enter that user’s password and successfully display the user’s Desktop. The LightDM GTK+ Greeter screen no longer hangs/freezes every time.

When more than one user is logged in (i.e. there is more than one session), the PC will suspend automatically if there is no user activity in a particular session during the configured timeout period for that session. Pressing a key on the USB keyboard will then wake the PC and display the LightDM GTK+ Greeter screen. The desired username can then be selected and the corresponding password entered. The following is an example of the sort of thing that can happen:

  • User fitzcarraldo (timeout configured as 30 minutes) logs in to his account at 09:00 and uses the PC until he locks his session manually (Ctrl+Alt+L) at 09:11.
  • User paul (timeout configured as 15 minutes) logs in to his account at 09:15 and uses the PC until he locks his session manually at 09:23.
  • User molly (timeout configured as 45 minutes) logs in to her account at 09:25 and uses the PC for several hours.
  • At 09:38, while user molly is using the PC, the PC automatically suspends to RAM (15 minutes after user paul stopped using his session). User molly has to wake the PC from suspension. Nothing is lost.
  • At 09:41, while user molly is using the PC, the PC automatically suspends to RAM (30 minutes after user fitzcarraldo stopped using his session). User molly has to wake the PC from suspension. Nothing is lost.

To avoid scenarios such as the above, if a user does not need the session any longer it is better to log out rather than leave the session in existence.

How to display a user’s avatar instead of the generic avatar on the LightDM GTK Greeter screen in Lubuntu 17.10

I recently installed Lubuntu 17.10 on my family’s PC (single-seat, multi-user). The default avatar was displayed for each user on the LightDM greeter screen, rather than each user’s individual avatar. I have experienced this problem in more than one Linux distribution (Gentoo, Sabayon and now Lubuntu 17.10), more than one Desktop Environment (KDE, GNOME and now LXDE), and more than one Display Manager (LightDM and SDDM), so my suspicion is that the problem lies with AccountsService rather than the DE or DM. Anyway, here is how I fixed the problem in Lubuntu 17.10. The example below is for user fitzcarraldo, and I used the same procedure for each username in the installation.

1. Create a 96×96 PNG avatar /home/fitzcarraldo/Pictures/fitzcarraldo.png

2. Edit the file /var/lib/AccountsService/users/fitzcarraldo to contain the following:

[User]
XSession=Lubuntu
SystemAccount=false
Icon=/var/lib/AccountsService/icons/fitzcarraldo	

3. Make sure that the file has 644 permissions:

$ ls -la /var/lib/AccountsService/users/fitzcarraldo
-rw-r--r-- 1 root root 85 Jan  1 02:53 /var/lib/AccountsService/users/fitzcarraldo

4. Copy the avatar to the relevant directory and make sure it has 644 permissions:

$ sudo cp /home/fitzcarraldo/Pictures/fitzcarraldo.png /var/lib/AccountsService/icons/fitzcarraldo
$ ls -la /var/lib/AccountsService/icons/fitzcarraldo
-rw-r--r-- 1 root root 14860 Jan  1 02:54 /var/lib/AccountsService/icons/fitzcarraldo

After rebooting, the desired avatar should be displayed on LightDM’s GTK Greeter screen.

Background reading

  1. KDE Bug Report No. 336994 – User Manager does not show one particular user in the list unless I login as that user
  2. Gentoo Forums – user-manager in plasma desktop not populating users
  3. Gentoo Forums – LightDM greeter username in list stuck and can’t add others