Setting the wireless regulatory domain in Linux on your laptop
January 20, 2013 5 Comments
I travel internationally and want to make sure that my laptop uses the legal wireless networking frequencies in the country I am visiting. In Linux, CRDA (Central Regulatory Domain Agent) is the udev helper used to communicate between userspace and the kernel, and it enables you to view and alter the wireless regulatory domain your kernel uses. For more information see the Regulatory page on the Linux Wireless Wiki site.
CFG80211 is the Linux wireless LAN (802.11) configuration API. The kernel on my main laptop has the following configuration settings relating to CFG80211:
# cat /usr/src/linux/.config | grep CFG80211
CONFIG_CFG80211=m
# CONFIG_CFG80211_DEVELOPER_WARNINGS is not set
# CONFIG_CFG80211_REG_DEBUG is not set
CONFIG_CFG80211_DEFAULT_PS=y
# CONFIG_CFG80211_DEBUGFS is not set
# CONFIG_CFG80211_INTERNAL_REGDB is not set
CONFIG_CFG80211_WEXT=y
and the cfg80211 module is loaded:
# lsmod | grep cfg80211
cfg80211 145747 3 iwlwifi,mac80211,iwldvm
I have the package crda installed, and I have the following udev rule file /etc/udev/rules.d/regulatory.rules to allow the kernel to communicate with userspace:
KERNEL=="regulatory*", ACTION=="change", SUBSYSTEM=="platform", RUN+="/sbin/crda"
So, how do you check which wireless regulatory domain your kernel is currently using, and switch to another domain if necessary? These tasks are performed using the iw command. You’ll need to install the package iw if it is not already installed.
To see the regulatory domain your laptop is using now, enter the following command as root user:
iw reg get
When I use the above command on my laptop after start-up, I normally see the following:
# iw reg get
country 00:
(2402 - 2472 @ 40), (3, 20)
(2457 - 2482 @ 20), (3, 20), PASSIVE-SCAN, NO-IBSS
(2474 - 2494 @ 20), (3, 20), NO-OFDM, PASSIVE-SCAN, NO-IBSS
(5170 - 5250 @ 40), (3, 20), PASSIVE-SCAN, NO-IBSS
(5735 - 5835 @ 40), (3, 20), PASSIVE-SCAN, NO-IBSS
The country code 00 is not the code of the country I am in at present. To tell the kernel which wireless regulatory domain you wish to use, enter the following command as root user:
iw reg set ISO_3166-1_alpha-2
where ISO_3166-1_alpha-2 is the 2-character code for the country you are in. You can find the list of ISO 3166-1 alpha-2 codes on the Wikipedia page ISO 3166-1 alpha-2.
For example, if I were in the UK then I would enter the following command:
# iw reg set GB
and the regulatory domain would then be reported like this:
# iw reg get
country GB:
(2402 - 2482 @ 40), (N/A, 20)
(5170 - 5250 @ 40), (N/A, 20)
(5250 - 5330 @ 40), (N/A, 20), DFS
(5490 - 5710 @ 40), (N/A, 27), DFS
It is not a big deal to use the command line, but I wanted to make it even easier. I’m using KDE on my main laptop, so I created a Desktop Configuration File /home/fitzcarraldo/Desktop/Set_wireless_regulatory_domain containing the following:
[Desktop Entry] Comment[en_GB]= Comment= Exec=/home/fitzcarraldo/iw_reg.sh GenericName[en_GB]=Set wireless regulatory domain GenericName=Set wireless regulatory domain Icon=/home/fitzcarraldo/national-flags-icon.png MimeType= Name[en_GB]=Set_wireless_regulatory_domain Name=Set_wireless_regulatory_domain Path= StartupNotify=true Terminal=true TerminalOptions=\s--noclose Type=Application X-DBUS-ServiceName= X-DBUS-StartupType=none X-KDE-SubstituteUID=false X-KDE-Username=
and gave it the following file permissions:
# chmod 744 /home/fitzcarraldo/Desktop/Set_wireless_regulatory_domain
# ls -la /home/fitzcarraldo/Desktop/Set_wireless_regulatory_domain
-rwxr--r-- 1 fitzcarraldo users 496 Jan 15 21:53 /home/fitzcarraldo/Desktop/Set_wireless_regulatory_domain
I used a search engine to find a nice PNG icon consisting of several overlapping national flags, and saved it with the file name name national-flags-icon.png in my home directory.
I created a Bash shell script /home/fitzcarraldo/iw_reg.sh containing the following:
#!/bin/bash echo "First you need to enter the password of your user account..." sudo echo "" echo "The ISO 3166-1 alpha-2 codes are listed on Web page https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2" echo "" echo "The current wireless regulatory domain is set as: " echo "" sudo iw reg get echo "" echo -n "Enter the ISO 3166-1 alpha-2 code (upper case) for the country you are in now, and press ENTER: " read REGULATORYDOMAIN sudo iw reg set $REGULATORYDOMAIN echo "" echo "The current wireless regulatory domain is now set as: " echo "" sudo iw reg get echo "" echo "All done. You can close this window."
and gave it the following file permissions:
# chmod 744 /home/fitzcarraldo/iw_reg.sh
# ls -la /home/fitzcarraldo/iw_reg.sh
-rwxr--r-- 1 fitzcarraldo users 632 Jan 15 21:33 /home/fitzcarraldo/iw_reg.sh
Now, if I double-click on the icon for Set_wireless_regulatory_domain on my desktop, a Konsole window pops up with a prompt for me to enter my user account password. When I enter my password the window displays the current wireless regulatory domain the kernel is using and prompts me to enter the 2-character code for the regulatory domain I wish to use instead. When I enter the country code the window displays the new regulatory domain, as shown in the sample below.
First you need to enter the password of your user account...
Password:The ISO 3166-1 alpha-2 codes are listed on Web page https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2
The current wireless regulatory domain is set as:
country SA:
(2402 - 2482 @ 40), (N/A, 20)
(5170 - 5250 @ 20), (3, 23)
(5250 - 5330 @ 20), (3, 23), DFS
(5735 - 5835 @ 20), (3, 30)Enter the ISO 3166-1 alpha-2 code (upper case) for the country you are in now, and press ENTER: GB
The current wireless regulatory domain is now set as:
country GB:
(2402 - 2482 @ 40), (N/A, 20)
(5170 - 5250 @ 40), (N/A, 20)
(5250 - 5330 @ 40), (N/A, 20), DFS
(5490 - 5710 @ 40), (N/A, 27), DFSAll done. You can close this window.
The task of viewing and changing the regulatory domain after start-up is now very easy for me. The only thing that would be easier than this would be if Linux could detect automatically which country I’m in and set the regulatory domain automatically.
EDIT (July 10, 2015): Note the following restriction when changing the regulatory domain: Helping compliance by allowing to change regulatory domains. See also the Gentoo Forums thread [solved] Atheros and regulatory domain.
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