With this we can stabilize how naming works for network interfaces. A
user can request through a kernel cmdline option or an env var which
scheme to follow. The idea is that installers use this to set into stone
(a very soft stone though) the scheme used during installation so that
interface naming doesn't change afterwards anymore.
Why use env vars and kernel cmdline options, and not a config file of
its own?
Well, first of all there's no obvious existing one to use. But more
importantly: I have the feeling that this logic is kind of an incomplete
hack, and I simply don't want to do advertise this as a perfectly
working solution. So far we used env vars for the non-so-official
options and proper config files for the official stuff. Given how
incomplete this logic is (i.e. the big variable for naming remains the
kernel, which might expose sysfs attributes in newer versions that we
check for and didn't exist in older versions — and other problems like
this), I am simply not confident in giving this first-class exposure in
a primary configuration file.
Fixes: #10448
Before:
Assertion 'mknod(devname, mode, devnum) == 0' failed at ../src/test/test-udev.c:116, function run(). Aborting.
Assertion 'unlink(devname) == 0' failed at ../src/test/test-udev.c:118, function run(). Aborting.
After:
mknod() failed for '/dev/sda': Operation not permitted
unlink('/dev/sda') failed: No such file or directory
cg_ns_supported() caches, so the condition was really checked just once, but
it looks weird to assign the return value to arg_use_cgns (if the variable is not present),
because then the other checks are effectively equivalent to
if (cg_ns_supported() && cg_ns_supported()) { ...
and later
if (!cg_ns_supported() || !cg_ns_supported()) { ...
This imports the wiki page for predictable interface names. I think it's
useful to preserve history here because it's a contentious subject, and
it's useful to know when what happened.
Lennart Poettering
Chris Down
Alexey Bogdanenko
Zbigniew Jędrzejewski-Szmek
Evgeny Vereshchagin
LennartPoettering
TanuKaskinen
ColinGuthrie
Joe Rayhawk
LennartPoettering
127.0.0.1