CRDA(8) Linux CRDA(8)
crda - send to the kernel a wireless regulatory domain for a given ISO
/ IEC 3166 alpha2
crda is the Linux wireless central regulatory domain agent. crda is
intended to be used by udev scripts and should not be run manually
unless debugging udev scripts. crda is triggered to run by the kernel
by sending a udev event upon a new regulatory domain change. Regulatory
domain changes are triggered by the wireless kernel subsystem (upon
initialization and on reception of country IEs), wireless drivers, or
userspace (see iw ). Upon a regulatory domain change the kernel sends a
udev change event for the regulatory platform. The kernel ignores regu-
latory domains sent to it if it does not expect them. The regulatory
domain is read by crda from the regulatory.bin file.
RSA Digital Signature
If built with openssl or gcrypt support crda will have embedded into it
an RSA digital signature which will prevent it from reading corrupted
or non-authored regulatory.bin files. Authorship is respected by the
RSA public key packed into crda. This specific crda package has been
built with an RSA public key from John Linville (the Linux wireless
kernel maintainer) and as such will only read regulatory.bin files
signed by him. For further information see the regulatory.bin man page.
A udev regulatory rule must be put in place in order to receive and
parse udev events from the kernel in order to get udev to call crda
with the passed ISO / IEC 3166 alpha2 country code. An example udev
rule which can be used (usually in /lib/udev/rules.d/85-regula-
KERNEL=="regulatory*", ACTION=="change", SUBSYSTEM=="platform",
Set the COUNTRY environment variable with a specific ISO / IEC 3166
alpha2 country code and then run crda without arguments. This will send
a regulatory domain for that alpha2 to the kernel.
crda 23 January 2009 CRDA(8)
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