As of about a week ago, my cron daemon refuses to stay running. I'm using Debian 6. Running something like pgrep cron shows that the daemon isn't running. I start the service with service cron start or /etc/init.d/cron start and it launches, but it disappears from the running process list after a few minutes (varying anywhere between 1 - 30 minutes before the process is killed again).
Using strace -f service cron start, I can see that the process is being killed for some reason:
nanosleep({56, 0}, 0x7fffa7184c80) = 0
stat("crontabs", {st_mode=S_IFDIR|S_ISVTX|0730, st_size=4096, ...}) = 0
stat("/etc/crontab", {st_mode=S_IFREG|0644, st_size=1100, ...}) = 0
stat("/etc/cron.d", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
stat("/etc/cron.d/php5", {st_mode=S_IFREG|0644, st_size=475, ...}) = 0
stat("/etc/cron.d/anacron", {st_mode=S_IFREG|0644, st_size=244, ...}) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigaction(SIGCHLD, NULL, {0x4036f0, [CHLD], SA_RESTORER|SA_RESTART, 0x2b0e8465f230}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
nanosleep({60, 0}, <unfinished ...>
+++ killed by SIGKILL +++
There's nothing relevant in /var/log/syslog, /var/log/messages, /var/log/auth.log, or /var/log/kern.log to explain why the the process is dying. The system has about 500 MB of free memory, and cat /proc/loadavg returns 0.10 0.21 0.45 so resources shouldn't be the issue. I also tried removing and reinstalling the cron package using apt-get. What else should I check? How do I find out what's killing my crond?
Edit: I'm on a virtual machine under OpenVZ (and as such, I have no swap). With cron running, free -m reports:
total used free shared buffers cached
Mem: 1024 465 558 0 0 0
-/+ buffers/cache: 465 558
Swap: 0 0 0
My OpenVZ User Beancounters via cat /proc/user_beancounters:
Version: 2.5
uid resource held maxheld barrier limit failcnt
172087: kmemsize 8275718 25561636 51200000 51200000 0
lockedpages 0 968 2048 2048 0
privvmpages 113442 266465 262200 262200 3740757
shmpages 788 4004 128000 128000 0
dummy 0 0 0 0 0
numproc 39 98 600 600 0
physpages 50521 208434 0 9223372036854775807 0
vmguarpages 0 0 512000 512000 0
oomguarpages 50521 208447 512000 512000 0
numtcpsock 7 323 4096 4096 0
numflock 7 64 2048 2048 0
numpty 1 4 32 32 0
numsiginfo 0 23 1024 1024 0
tcpsndbuf 137984 17878480 20480000 20480000 0
tcprcvbuf 114688 6983504 20480000 20480000 0
othersockbuf 162960 1074440 20480000 20480000 0
dgramrcvbuf 0 24208 10240000 10240000 0
numothersock 101 353 2048 2048 0
dcachesize 459171 747444 10240000 10240000 0
numfile 1010 4221 50000 50000 0
dummy 0 0 0 0 0
dummy 0 0 0 0 0
dummy 0 0 0 0 0
numiptent 39 424 2048 2048 0
