cgroup-bin daemon (cgred) doesn't work

[ocwo92]

I can't get the cgred daemon, which applies control group rules, to work.

My cgroup environment appears to be fine; at least cgexec applies the proper control groups as expected. However, the cgred daemon seems to completely ignore the rules.

The /etc/cgrules.conf file contains:


testuser:unrar cpu batchjob/

and when the cgred daemon is started in debug mode, it reveals that it parses the rule:


testuser@home:$ sudo cgrulesengd -d
CGroup Rules Engine Daemon log started
Current time: Thu May 24 13:43:20 2012

Opened log file: -, log facility: 0, log level: 7
Proceeding with PID 23393
Rule: testuser:unrar
UID: 1000
GID: N/A
DEST: batchjob/
CONTROLLERS:
cpu

Started the CGroup Rules Engine Daemon.
:

However, when testuser starts an unrar command that lasts several minutes, the cgrulesengd log shows no indication whatsoever that unrar is being run, let alone being classified as cpu:batchjob.

The log does indicate that cgrulesengd receives some events (apparently making it unrelated to this bug (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=609004)), because it contains output such as:


Cgroup change for PID: 24935, UID: 118, GID: 126, PROCNAME: /usr/lib/nagios/plugins/check_all_procr.sh OK
EXEC Event: PID = 24938, tGID = 24938
Cgroup change for PID: 24938, UID: 118, GID: 126, PROCNAME: /usr/bin/tr OK
EXEC Event: PID = 24939, tGID = 24939
Cgroup change for PID: 24939, UID: 118, GID: 126, PROCNAME: /usr/bin/wc OK
EXEC Event: PID = 24942, tGID = 24942
Cgroup change for PID: 24942, UID: 118, GID: 126, PROCNAME: /usr/bin/tr OK
EXEC Event: PID = 24943, tGID = 24943
Cgroup change for PID: 24943, UID: 118, GID: 126, PROCNAME: /bin/ps OK

But, no mention of unrar. How do I make it work?

[ocwo92]

I got a little closer to the reason why the rules daemon fails. I notized that with unzip instead of unrar, the process is recognized and reclassified. The reason seems to be that unrar is part of the alternatives system, that is, /usr/bin/unrar is a symbolic link to /etc/alternatives/unrar, which in turn is a symbolic link to /usr/bin/unrar-nonfree. So, by entering unrar-nonfree in the rules file and executing unrar-nonfree instead of unrar, the process is recognized by cgred and reclassified.

However, I have to call unrar-nonfree explicitly; it doesn't suffice to enter unrar-nonfree in the rules file.

How might I work around this problem?

[ocwo92]

Bingo. According to some emails on the libcg development list (http://www.mail-archive.com/libcg-devel@lists.sourceforge.net/msg03253.html), the rules engine daemon doesn't handle symbolic links properly.

Hopefully the fix will be included soon in the Ubuntu repositories; in the meantime I might want to build the package myself and include the patch.

[ocwo92]

in the meantime I might want to build the package myself and include the patch.

And so, version 0.83rc1 of the libcgroup1 package is now available as a PPA here: https://launchpad.net/~ole.wolf/+archive/libcgroup. Note that this package include the daemons otherwise found in the cgroup-bin package in the current distribution.

Edit: as of this writing, the repository doesn't seem to have published the files yet. I'm sure this will happen within a few hours.