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 run KDE Dolphin, Kate and KWrite as root user

When using KDE I occasionally wish to launch KWrite or Kate as root user in order to edit system files more easily than using a TUI editor in a terminal window (either launched as root user or by using the sudoedit command). Being able to browse using Dolphin as the root user occasionally is also useful. These all used to be possible by launching the application with the kdesu command, but in 2017 KDE developer Martin Gräßlin removed this option on security grounds (see his blog post ‘Editing files as root‘). Attempting to launch e.g. Kate using the sudo command results in the following message:

$ sudo kate
Executing Kate with sudo is not possible due to unfixable security vulnerabilities.

Attempting to launch e.g. Kate using the kdesu command results in a pop-up window prompting me to enter the root user’s password, but then does not launch Kate:

$ kdesu kate
$

I am willing to accept a small risk despite the ‘unfixable security vulnerabilities’ , and a 2018 Kubuntu Forums post by KDE user Rog131 provided me with a solution. It is possible to launch Dolphin, Kate and KWrite as root from your user account by using the pkexec command. For example, to launch Dolphin you can enter:

$ pkexec env DISPLAY=$DISPLAY XAUTHORITY=$XAUTHORITY KDE_SESSION_VERSION=5 KDE_FULL_SESSION=true dolphin

Dolphin first displays an orange-coloured box with the warning message ‘Running Dolphin as root can be dangerous. Please be careful.’ and you can then browse and open root-owned directories and files.

You can also launch Kate and KWrite as root from your user account in the same way:

$ pkexec env DISPLAY=$DISPLAY XAUTHORITY=$XAUTHORITY KDE_SESSION_VERSION=5 KDE_FULL_SESSION=true kate
$ pkexec env DISPLAY=$DISPLAY XAUTHORITY=$XAUTHORITY KDE_SESSION_VERSION=5 KDE_FULL_SESSION=true kwrite

To make it easy to launch them as root user from e.g. Konsole or Yakuake you could set aliases for the three commands in your ~/.bashrc file:

$ tail -n 3 ~/.bashrc
alias dolroot="pkexec env DISPLAY=$DISPLAY XAUTHORITY=$XAUTHORITY KDE_SESSION_VERSION=5 KDE_FULL_SESSION=true dolphin"
alias kateroot="pkexec env DISPLAY=$DISPLAY XAUTHORITY=$XAUTHORITY KDE_SESSION_VERSION=5 KDE_FULL_SESSION=true kate"
alias kwriteroot="pkexec env DISPLAY=$DISPLAY XAUTHORITY=$XAUTHORITY KDE_SESSION_VERSION=5 KDE_FULL_SESSION=true kwrite"

Then all you would need to type in a terminal window would be:

$ dolroot
$ kateroot
$ kwriteroot

which are no more difficult than having to type:

$ kdesu dolphin
$ kdesu kate
$ kdesu kwrite

If an alias is used, rooted-Dolphin/Kate/KWrite can be launched from the command line but cannot be launched via KDE’s Application Launcher menu or KRunner. On the other hand, if a wrapper script is used, rooted-Dolphin/Kate?KWrite can be launched from the user’s command line and via KDE’s Application Launcher menu (and therefore via KRunner too). For example, I created three tiny Bash scripts dolroot, kateroot and kwriteroot. The scripts simply contain the aforementioned pkexec command. For example, dolroot contains:

#!/bin/bash
pkexec env DISPLAY=$DISPLAY XAUTHORITY=$XAUTHORITY KDE_SESSION_VERSION=5 KDE_FULL_SESSION=true dolphin

Don’t forget to make them executable:

$ chmod 700 dolroot
$ chmod 700 kateroot
$ chmod 700 kwriteroot
$ ls -la *root
-rwx------ 1 fitzcarraldo fitzcarraldo 115 Jul 30 15:33 dolroot
-rwx------ 1 fitzcarraldo fitzcarraldo 112 Jul 30 15:34 kateroot
-rwx------ 1 fitzcarraldo fitzcarraldo 114 Jul 30 15:34 kwriteroot	

After adding entries for dolroot, kateroot and kwriteroot to the KDE Application Launcher’s menu, you can press Alt+F2 as usual to display the KRunner launcher then enter ‘dolroot’, ‘kateroot’ or ‘kwriteroot’ (without the quotes, obviously) in the KRunner window to launch Dolphin/Kate/KWrite as root user. A window will pop-up for you to enter the root user’s password. Once you have entered the root user’s password, the application will be launched.

Thankfully KDE’s Nathaniel Graham is pragmatic:

D12795 – Re-allow running Dolphin as the root user (but still not using sudo)
D12732 – Show a warning when running as the root user

How to change the height of the Kickoff Application Launcher menu in KDE Plasma

The height of the KDE Plasma Kickoff Application Launcher menu is not user-configurable, which is odd in a Desktop Environment with a reputation for being highly user-configurable.

It turns out that the height and width of the pop-up menu are hard-coded in the ASCII file /usr/share/plasma/plasmoids/org.kde.plasma.kickoff/contents/ui/FullRepresentation.qml:

root # grep -E "Layout.minimumHeight.*units.gridUnit" /usr/share/plasma/plasmoids/org.kde.plasma.kickoff/contents/ui/FullRepresentation.qml
    Layout.minimumHeight: units.gridUnit * 34
root # grep -E "Layout.minimumWidth.*units.gridUnit" /usr/share/plasma/plasmoids/org.kde.plasma.kickoff/contents/ui/FullRepresentation.qml
    Layout.minimumWidth: units.gridUnit * 26

Now, I was a bit fed up having to scroll up and down the launcher menu to see all fourteen entries in my Favourites list, so I decided to increase the height of the menu, which I did by editing /usr/share/plasma/plasmoids/org.kde.plasma.kickoff/contents/ui/FullRepresentation.qml as root user:

root # nano /usr/share/plasma/plasmoids/org.kde.plasma.kickoff/contents/ui/FullRepresentation.qml
root # grep -E "Layout.minimumHeight.*units.gridUnit" /usr/share/plasma/plasmoids/org.kde.plasma.kickoff/contents/ui/FullRepresentation.qml
    Layout.minimumHeight: units.gridUnit * 44

The only downside to this is that the file will be overwritten when the package kde-plasma/plasma-desktop is upgraded.

The following command would allow me to make sure the file contains the height value of ’44’ that I want:

root # sed -i '/Layout.minimumHeight: units.gridUnit/ c\    Layout.minimumHeight: units.gridUnit * 44' /usr/share/plasma/plasmoids/org.kde.plasma.kickoff/contents/ui/FullRepresentation.qml

Therefore, to automate the editing of the file in my Gentoo installations that use OpenRC I created a shell script /etc/local.d/50-set_Kickoff_height.start with the following contents:

#!/bin/bash
if [ -e /usr/share/plasma/plasmoids/org.kde.plasma.kickoff/contents/ui/FullRepresentation.qml ]; then
    sed -i '/Layout.minimumHeight: units.gridUnit/ c\    Layout.minimumHeight: units.gridUnit * 44' /usr/share/plasma/plasmoids/org.kde.plasma.kickoff/contents/ui/FullRepresentation.qml
fi

The FullRepresentation.qml file will then be edited every time the machine boots, which is a tad inefficient but not a big overhead.

This is not a perfect solution because the menu will revert to its default height following an upgrade to the package kde-plasma/plasma-desktop until I reboot the machine, but it is good enough for me.

KDE Device Notifier work-around

KDE Device Notifier can be annoying sometimes. The problem is that clicking on the Eject icon in Device Notifier (tooltip ‘Click to safely remove this device’) both unmounts and ejects the device (two separate commands). Of course, in the case of a USB device the device remains physically connected until you pull out the USB plug. You cannot re-mount the device in KDE Device Notifier until you unplug it and plug it in again. However, there is a hack that can help somewhat, as I explain below.

Firstly, note that it is possible to mount and unmount drives by using the ‘udisksctl’ command. For example, consider one of my USB HDDs which has the label ‘USBHDD01’ (I assign a label to all HDD partitions, be they on internal HDDs or on external HDDs/pendrives). It is possible to unmount the specific USB device and remount it by using the following commands:

fitzcarraldo@clevow230ss ~ $ udisksctl unmount -b /dev/disk/by-label/USBHDD01
Unmounted /dev/sdb1.
fitzcarraldo@clevow230ss ~ $ udisksctl mount -b /dev/disk/by-label/USBHDD01
Mounted /dev/sdb1 at /run/media/fitzcarraldo/USBHDD01.

In both the above cases the USB device remains visible in Device Notifier. I have created a couple of executable Desktop Configuration Files in the directory ~/Desktop/ which I can double-click to run each of the above commands. I have given each of them an appropriate icon:

The file ~/Desktop/Mount_USBHDD01.desktop contains the following:

[Desktop Entry]
Comment[en_GB]=Mount USB HDD with label USBHDD01
Comment=Mount USB HDD with label USBHDD01
Exec=udisksctl mount -b /dev/disk/by-label/USBHDD01
GenericName[en_GB]=Mount_USBHDD01
GenericName=Mount_USBHDD01
Icon=media-mount
MimeType=
Name[en_GB]=Mount_USBHDD01
Name=Mount_USBHDD01
Path=
StartupNotify=true
Terminal=false
TerminalOptions=
Type=Application
X-DBUS-ServiceName=
X-DBUS-StartupType=none
X-KDE-SubstituteUID=false
X-KDE-Username=fitzcarraldo

The file ~/Desktop/Unmount_USBHDD01.desktop contains the following:

[Desktop Entry]
Comment[en_GB]=Unmount USB HDD with label USBHDD01
Comment=Unmount USB HDD with label USBHDD01
Exec=udisksctl unmount -b /dev/disk/by-label/USBHDD01
GenericName[en_GB]=Unmount_USBHDD01
GenericName=Unmount_USBHDD01
Icon=media-eject
MimeType=
Name[en_GB]=Unmount_USBHDD01
Name=Unmount_USBHDD01
Path=
StartupNotify=true
Terminal=false
TerminalOptions=
Type=Application
X-DBUS-ServiceName=
X-DBUS-StartupType=none
X-KDE-SubstituteUID=false
X-KDE-Username=fitzcarraldo

(N.B. Since I could not find a media-unmount icon, I have used the media-eject icon to represent Unmount.)

This is not perfect in the sense that the device will still disappear from Device Notifier if you click on the Eject icon in Device Notifier. But at least I can avoid doing that until I really do want to unplug the device from my laptop. In other cases I simply double-click on the Mount_USBHDD01 icon and Unmount_USBHDD01 icon on my Desktop to mount and unmount the USB device as many times as I need to.

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

Configure a keyboard shortcut in Lubuntu 18.04 to take a screenshot of a screen region

As installed, Lubuntu 18.04 is configured so that the user can capture a screenshot of the whole screen by pressing the PrtScrn key, and a screenshot of the active window by pressing Alt+PrtScrn. However, no keyboard shortcut is configured to enable the user to capture a user-specified region of the screen.

Now, as it happens, the ‘-s‘ option of the scrot command allows a region of the screen to be captured and saved. The man page for scrot tells us:

-s, --select
Interactively select a window or rectangle with the mouse.

So here is how to configure a keyboard shortcut to do that in Lubuntu 18.04.

Open the file ~/.config/openbox/lubuntu-rc.xml in a text editor (either nano from the command line or LXTerminal from the GUI) and look for the following lines:

    <keybind key="Print">
      <action name="Execute">
        <command>lxsession-default screenshot</command>
      </action>
    </keybind>
    <keybind key="A-Print">
      <action name="Execute">
        <command>lxsession-default screenshot window</command>
      </action>
    </keybind>

Append the following lines to that group of lines:

    <keybind key="C-A-Print">
      <action name="Execute">
        <command>scrot -s</command>
      </action>
    </keybind>

The new group of lines should then look like this:

    <keybind key="Print">
      <action name="Execute">
        <command>lxsession-default screenshot</command>
      </action>
    </keybind>
    <keybind key="A-Print">
      <action name="Execute">
        <command>lxsession-default screenshot window</command>
      </action>
    </keybind>
    <keybind key="C-A-Print">
      <action name="Execute">
        <command>scrot -s</command>
      </action>
    </keybind>

Now logout and login again.

If you now press Ctrl+Alt+PrtScrn and use your mouse to select a rectangular region of the screen, a screenshot of that region will be saved automatically to your home directory. Simple.

You just have to remember:

PrtScrn — Captures the entire screen.
Alt+PrtScrn — Captures the active window.
Ctrl+Alt+PrtScrn — Captures the area of the screen you select with the mouse.

Installing Dropbox in Gentoo Linux following the recent restrictions introduced for Dropbox for Linux

In a 2013 post I explained how I installed Dropbox in Gentoo Linux running KDE 4. The Dropbox company has recently imposed some restrictions in the Linux client, so this is to explain what I did to get Dropbox working again in my two Gentoo Linux installations, both using the ext4 filesystem (unencrypted) and, these days, KDE Plasma 5.

Both my laptops running Gentoo Linux had a version of Dropbox installed via the Portage package manager: dropbox-45.3.88 in the case of the laptop running Gentoo amd64, and dropbox-48.3.56 in the case of the laptop running Gentoo ~amd64. Recently a Dropbox window popped up, warning me to upgrade Dropbox to the latest version within seven days otherwise the client would no longer be able to sync with the remote Dropbox server. I also received an e-mail from the Dropbox company titled ‘[Action required] We’re updating Linux system requirements‘ informing me that the only supported Linux distributions from now on would be Ubuntu 14.04 or higher and Fedora 21 or higher, and furthermore that the client will only work on an unencrypted ext4 filesystem. As both my Gentoo installations use unencrypted ext4, I was OK on that score, but I still had the problem that an up-to-date Dropbox ebuild is not available for Gentoo and the old Dropbox versions I was using no longer sync. However, I managed to install the latest version of Dropbox (currently 55.4.171) in Gentoo, and it works fine. The Dropbox client’s icon is on the KDE Plasma 5 Panel, and the local Dropbox directory is being sync’ed correctly. Below I explain what I did.

1. I selected ‘Quit Dropbox’ from the old Dropbox client’s menu, and the Dropbox icon disappeared from the Panel.

2. I removed the Dropbox daemon from the list of script files to be started at login (‘System Settings’ > ‘Startup and Shutdown’ > ‘Autostart’).

3. I unmerged (uninstalled) the dropbox package:

clevow230ss /home/fitzcarraldo # emerge --ask --depclean dropbox

4. I deleted the directories ~/.dropbox and ~/.dropbox-dist but kept the directory ~/Dropbox and its contents.

fitzcarraldo@clevow230ss ~ $ rm -rf ~/.dropbox ~/.dropbox-dist

5. I followed the instructions under ‘Dropbox Headless install via command line‘ on the Dropbox Website to re-install the latest version of the daemon and client:

fitzcarraldo@clevow230ss ~ $ cd ~ && wget -O - "https://www.dropbox.com/download?plat=lnx.x86_64" | tar xzf -

6. I configured KDE Plasma 5 to start ~/.dropbox-dist/dropboxd at login (‘System Settings’ > ‘Startup and Shutdown’ > ‘Autostart’ > ‘Add Script…’).

7. I launched ~/.dropbox-dist/dropboxd manually from a Konsole window. The Dropbox client icon appeared on the Panel and I was prompted to login to my Dropbox account via a Web browser, as per the instructions on the Dropbox Website (see link in in Step 5):

If you’re running Dropbox on your server for the first time, you’ll be asked to copy and paste a link in a working browser to create a new account or add your server to an existing account. Once you do, your Dropbox folder will be created in your home directory.

8. I logged in to my Dropbox account via the Firefox browser. As soon as I had logged in via the browser, a message appeared in the browser window informing me that “Your computer was successfully linked to your account”, and the Dropbox client icon appeared on the Panel and showed that the contents of ~/Dropbox were being synchronised.

Everything seems to be working as before. The Dropbox icon on the Panel has the same menu items it had previously. ‘Preferences…’ shows the Dropbox version as v55.4.171. I have not ticked ‘Start Dropbox on system startup’ under Dropbox Preferences because I configured automatic startup using KDE Plasma 5 ‘System Settings’ as described in Step 6 above, and the Dropbox daemon is indeed started automatically when I login.

The Dropbox Website’s instructions (see link in Step 5) also include the following:

Download this Python script to control Dropbox from the command line. For easy access, put a symlink to the script anywhere in your PATH.

I did download that Python script and made it executable:

fitzcarraldo@clevow230ss ~/Dropbox $ chmod +x dropbox.py

However the Python 3.6 interpreter in my Gentoo Linux installations report a syntax error in the script when I run it, I assume because it was written for a different version of Python:

fitzcarraldo@clevow230ss ~/Dropbox $ ./dropbox.py 
  File "./dropbox.py", line 233
    except OSError, e:
                  ^
SyntaxError: invalid syntax

Anyway, as the Dropbox client icon is on the KDE Plasma 5 Panel and I can control Dropbox from there, I see no need for the Python script.

9. My Gentoo installations have a Bash script ~/dbox.sh that I had created to be launched by a Desktop Configuration file ~/Desktop/Dropbox.desktop with a nice icon which I double-click on if I want to relaunch the Dropbox daemon (if I previously quit Dropbox from the client’s menu, for example). I had to modify ~/dbox.sh by replacing the command ‘dbus-launch dropbox start > /dev/null‘ with the command ‘/home/fitzcarraldo/.dropbox-dist/dropboxd‘ as shown below.

dbox.sh

#!/bin/bash
notify-send 'Launching Dropbox' 'Daemon will be (re)started in 20 seconds' --icon=dialog-information
sleep 20s
ps auxww | awk '$0~/dropbox/&&$0!~/awk/{print $2}' | xargs kill
/home/fitzcarraldo/.dropbox-dist/dropboxd

Dropbox.desktop

[Desktop Entry]
Comment[en_GB]=(re)launch Dropbox daemon
Comment=(re)launch Dropbox daemon
Exec=/home/fitzcarraldo/dbox.sh
GenericName[en_GB]=Dropbox
GenericName=Dropbox
Icon=kipi-dropbox
MimeType=
Name[en_GB]=Dropbox
Name=Dropbox
Path=
StartupNotify=true
Terminal=false
TerminalOptions=
Type=Application
X-DBUS-ServiceName=
X-DBUS-StartupType=none
X-KDE-SubstituteUID=false
X-KDE-Username=fitzcarraldo

10. At the moment Dropbox is working fine again in my Gentoo installations. However, I noticed that Gentoo Linux user zsitvaij posted the following comment in a Gentoo Forums thread:

On every dropbox update, I have to remove ~/.dropbox-dist/dropbox-lnx./libdrm.so.2 to avoid having it crash on launch, works fine after until they update again.

I do not know if that will be necessary in my case, as I have not yet had to upgrade Dropbox from the Version 55.4.171 that I recently installed. When a new version of Dropbox becomes available I will update this post to confirm whether or not I had to do anything to keep Dropbox working.

Addendum (5 October 2019): With reference to my addendum of 31 August 2018, the Python script dropbox.py that can be downloaded from the Dropbox Web site has been updated and is now written in Python 3, so you can ignore my addendum of 31 August 2018.

Addendum (1 October 2018): With reference to my addendum of 2 September 2018, if you are using OpenRC it is possible to automate the deletion of the file ~/.dropbox-dist/dropbox-lnx.x86_64-/libdrm.so.2 by creating a Bash script /etc/local.d/40dropbox.start containing the following:

#!/bin/bash
if [ -e /home/fitzcarraldo/.dropbox-dist/dropbox-lnx.x86_64-*/libdrm.so.2 ]
then
    rm /home/fitzcarraldo/.dropbox-dist/dropbox-lnx.x86_64-*/libdrm.so.2
fi

Replace my username with your username, obviously. Of course the conditional test could be dispensed with and the script could just contain the shebang line and the rm line, which would still work even if the file does not exist, but it feels a bit tidier to only attempt to delete the file if it actually exists.

Addendum (2 September 2018): I have just installed Dropbox Version 56.4.94 in my Gentoo ~amd64 installation and I had to use the command shown below once in order to stop the daemon segfaulting when I entered the command ~/.dropbox-dist/dropboxd in a Konsole window:

fitzcarraldo@clevow230ss ~/Dropbox $ rm ~/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/libdrm.so.2

Addendum (31 August 2018): The Python script dropbox.py that can be downloaded from the Dropbox Web site (see Step 8 above) is old, as can be seen in the comments in the header of the script:

# Dropbox frontend script
# This file is part of nautilus-dropbox 2015.10.28.

It is written in Python 2. Although I do not need to use it, I managed to get it to run in my Gentoo installations by replacing the shebang line ‘#!/usr/bin/python‘ with ‘#!/usr/bin/env python2‘. This works in my Gentoo installations because they have both Python 2.7 and Python 3.6 installed. When I now run dropbox.py I see the following:

fitzcarraldo@clevow230ss ~/Dropbox $ ./dropbox.py 
Dropbox command-line interface

commands:

Note: use dropbox help  to view usage for a specific command.

 status       get current status of the dropboxd
 throttle     set bandwidth limits for Dropbox
 help         provide help
 stop         stop dropboxd
 running      return whether dropbox is running
 start        start dropboxd
 filestatus   get current sync status of one or more files
 ls           list directory contents with current sync status
 autostart    automatically start dropbox at login
 exclude      ignores/excludes a directory from syncing
 lansync      enables or disables LAN sync
 sharelink    get a shared link for a file in your dropbox
 proxy        set proxy settings for Dropbox

fitzcarraldo@clevow230ss ~/Dropbox $ ./dropbox.py status
Up to date
fitzcarraldo@clevow230ss ~/Dropbox $ ./dropbox.py running
fitzcarraldo@clevow230ss ~/Dropbox $ ./dropbox.py filestatus ~/Dropbox/Getting\ Started.pdf 
/home/fitzcarraldo/Dropbox/Getting Started.pdf: up to date
fitzcarraldo@clevow230ss ~/Dropbox $

Notice that the command ./dropbox.py running does not return anything even though the daemon is definitely running, so I do not trust the script anyway.

How to move a mouse pointer automatically in Linux to simulate user activity

My various Linux installations all have Suspend to RAM enabled with a specified timeout. Sometimes I want to override the timeout; for example if I have left something running in a terminal window or I have left the package manager in a virtual machine upgrading the guest installation. I could of course launch the system’s power manager GUI and temporarily disable Suspend to RAM or increase the timeout, but I prefer to use a shell script, launched by double-clicking on a Desktop icon, to move the mouse pointer automatically to fool the OS into believing someone is using the machine. There are various ways of doing this, but the method I prefer is given below.

1. Create a Bash script ‘/home/fitzcarraldo/keep_mouse_moving.sh‘ containing the following:

#!/bin/bash
#
# Script to keep mouse pointer moving so that, for example, Suspend to RAM timeout does not occur.
# 
# The mouse pointer will move around its current position on the screen, i.e. around any position
# on the screen where you place the pointer. However, if you prefer it to move around the centre
# of the screen then change mousemove_relative to mousemove in the xdotool command below.
#
# Set LENGTH to 0 if you do not want the mouse pointer to actually move.
# Set LENGTH to 1 if you want the mouse pointer to move just a tiny fraction.
# Set LENGTH to e.g. 100 if you want to see more easily the mouse pointer move.
LENGTH=1
#
# Set DELAY to the desired number of seconds between each move of the mouse pointer.
DELAY=5
#
while true
do
    for ANGLE in 0 90 180 270
    do
        xdotool mousemove_relative --polar $ANGLE $LENGTH
        sleep $DELAY
    done
done

Do not forget to make the script executable.

As you can see in the above script, it is possible to control how much, if at all, the mouse pointer actually moves on the screen. While the script is running you are not precluded from moving the mouse manually as well.

If you only want to prevent the OS from suspending while music is playing or you are watching a video (with audio), then a simple modification to the script can achieve that:

#!/bin/bash
#
# Script to keep mouse pointer moving while audio is playing so that, for example, Suspend to RAM timeout
# does not occur while listening to music or watching a video (with sound).
# 
# The mouse pointer will move around its current position on the screen, i.e. around any position
# on the screen where you place the pointer. However, if you prefer it to move around the centre
# of the screen then change mousemove_relative to mousemove in the xdotool command below.
#
# Set LENGTH to 0 if you do not want the mouse pointer to move.
# Set LENGTH to 1 if you want the mouse pointer to move just a tiny fraction.
# Set LENGTH to e.g. 100 if you want to see more easily the mouse pointer move.
LENGTH=1
#
# Set DELAY to the desired number of seconds between each move of the mouse pointer.
DELAY=5
#
while true
do
    if [[ `cat /proc/asound/card*/pcm*/sub*/status | grep RUNNING | wc -l` -ne 0 ]]; then
        for ANGLE in 0 90 180 270
        do
            xdotool mousemove_relative --polar $ANGLE $LENGTH
            sleep $DELAY
        done
    fi
done

2. Create a Desktop Configuration File ‘/home/fitzcarraldo/Desktop/keep_mouse_moving.desktop‘ containing the following:

[Desktop Entry]
Comment[en_GB]=Keep mouse moving automatically
Comment=Keep mouse moving automatically
Exec=xterm -iconic -e "bash -c /home/fitzcarraldo/keep_mouse_moving.sh"
GenericName[en_GB]=Keep mouse moving automatically
GenericName=Keep mouse moving automatically
Icon=input-mouse
MimeType=
Name[en_GB]=keep_mouse_moving
Name=keep_mouse_moving
Path=/home/fitzcarraldo
StartupNotify=true
Terminal=false
TerminalOptions=\s--noclose
Type=Application
X-DBUS-ServiceName=
X-DBUS-StartupType=none
X-LXDE-SubstituteUID=false
X-LXDE-Username=fitzcarraldo

(In installations that use KDE or GNOME I replace the ‘LXDE‘ above with ‘KDE‘ or ‘GNOME‘, as appropriate.)

3. Use the distribution’s package manager to install xterm and xdotool if they are not already installed.

4. Whenever I want to fool the OS into thinking a user is moving the mouse, I double-click on the mouse icon on the Desktop and the Bash script is launched in a minimised xterm window, which I can see on the Panel. I can then leave the installation knowing that it will not suspend to RAM and that the screensaver will not kick in. When I want to stop the mouse pointer moving automatically, I simply click on the xterm bar on the Panel to open the xterm window, and click on Close (×) on the window’s title bar to terminate xterm and the shell script.

Note that the X Windows Toolkit option -iconic may not work in some Desktop Environments (GNOME, for example), in which case you can minimise the xterm window manually if you want, or use another terminal emulator.

By the way, if you use GNOME and it is currently configured not to display icons on the Desktop, you can change this by using the following command:

user $ gsettings set org.gnome.desktop.background show-desktop-icons true

Of course you are not obliged to have the .desktop file on the Desktop; it could be in any directory.

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.