NOTE: this page is for archival only, see the note at the end of the page.

Central Regulatory Domain Agent

CRDA acts as the udev helper for communication between the kernel and userspace for regulatory compliance. It relies on nl80211 for communication. CRDA is intended to be run only through udev communication from the kernel. The user should never have to run it manually except if debugging udev issues.


CRDA is licensed under the ISC license in hopes other operating systems can benefit from a community project to enhance regulatory considerations.


You can get the latest CRDA code from:



You can get CRDA releases here

Host requirements

  • libc/ublibc
  • regulatory.bin file
  • libnl >= libnl1

Build requirements

  • python and the m2crypto package (python-m2crypto)
  • libgcrypt or libssl (openssl) header files
  • nl library and header files (libnl1 and libnl-dev) available at git://
  • RSA public key of John Linville, we include this as part of this package so you do not need to install it. This RSA public key comes from the wireless-regdb.git tree and we keep it up to date here.
  • regulatory database (regulatory.bin, no need to build just put the file in REG_BIN location) from:


Letting the kernel call CRDA

We use userspace events (uevents) to let the kernel speak to userspace. Below is an example udev rule you can place into your distribution's udev rules directory (usually /etc/udev/rules.d/). Note that most distributions have udev configured with inotify on the udev rules directory, so there is no need to restart udev after adding the new rule.

# Example file, should be put in /etc/udev/rules.d/regulatory.rules
KERNEL=="regulatory*", ACTION=="change", SUBSYSTEM=="platform", RUN+="/sbin/crda"

Changing regulatory domains

Userspace applications can request the kernel to change regulatory domains. The following userspace applications currently allow you to do this:

Using iw to change regulatory domains

You can use iw from the command line as follows:

iw reg set US

Using wpa_supplicant to change regulatory domains

Get the wpa_supplicant (as of 0.6.7) and then add as part of your configuration file a line that has something like this:


Using Network Manager to change regulatory domains

This needs to be implemented, but since Network Manager uses wpa_supplicant it should just be a matter of adding a user interface option to let a user select an alpha2 and then adding the country entry into the wpa_supplicant configuration entered.

Debugging kernel to CRDA communication

To debug communication between the kernel and udev you can monitor udev events:

udevadm monitor --environment kernel

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