it has been two weeks now since this strange encounter started. my linux based server hangs around the same time everyday.

I am aware that there is another thread on this forum with similar issue, but I have tried following the steps there and it didn't work for me.

Unfortunately I don't have enough experience to determine if this is a cron job problem or not. However I know of no new modifications to the software that could have caused this problem.

Any help will be highly appreciated.
Below is my server details:
Linux fedora release 9 sulphur
Ram 16 G
8 X Intel(R) Xeon(R) CPU E5420 @ 2.50GHz

thanks in advance

Look at ALL the crons on the machine, root, user, anything in /etc/cron.* and also check /var/log/messages and see if there's anything that runs around the time of your hang.

Does it actually crash or hang? I've seen similar problems where a server can become inaccessible due to it or an upstream router getting a new DHCP ip address assigned.

Does your server "come back" on its own or do you have to reboot it?

You can check different users crontab with 'crontab -u username -l'

I had corresponded with another gentleman JJJCR on this forum about this the other day, here's a list he commented might help:

"Other places to look for cron specific tasks would be the below locations:
/etc/crontab – provides specific details for cron including what the hourly, daily, weekly, and yearly cron tasks
/etc/cron.hourly – directory with hourly cron tasks
/etc/cron.daily – directory with daily cron tasks
/etc/cron.weekly – directory with weekly cron tasks
/etc/cron.monthly – directory with monthly cron tasks"

You can read the full thread here:
http://www.linuxquestions.org/questi...-crons-939570/

Also, be sure that you are checking the time stamps in /var/log/messages during the time that this occurs, to see just what is happening before the server hang.

thank you both for your quick reply.
it is a remote server when it hangs i can't ssh it, it has to be hardly rebooted.
however for business reasons we couldn't wait to check if the server is going to come back on its own, the longest we could wait was 45 mints.

we have checked the crontab for all users using the command "crontab -u username -l" and no crontab was found.

we also compared the cron log file with the /var/log/messages file and noticed the following:
1- the cron jobs started after the hard reboot.
2- no cron jobs mentioned in the messages file within the last 3 days.
3- the hang time is not accurate, it happens within an hour window.

--- here is the part of /var/log/messages file before and right after hang time:
Apr 26 15:31:35 secure kernel: audit(1335465095.536:131): audit_pid=0 old=2178 by auid=4294967295 subj=system_u:system_r:auditd_t:s0 res=1
Apr 26 15:31:35 secure kernel: type=1104 audit(1335465095.539:132): user pid=2694 uid=0 auid=0 subj=system_u:system_r:local_login_t:s0-s0:c0.c1023 msg='op=PAM:setcred acct="username" exe="/bin/login" (hostname=?, addr=?, terminal=tty1 res=success)'
Apr 26 15:31:35 secure kernel: type=1106 audit(1335465095.541:133): user pid=2694 uid=0 auid=0 subj=system_u:system_r:local_login_t:s0-s0:c0.c1023 msg='op=PAM:session_close acct="username" exe="/bin/login" (hostname=?, addr=?, terminal=tty1 res=success)'
Apr 26 15:31:35 secure kernel: type=1104 audit(1335465095.541:134): user pid=11097 uid=0 auid=0 subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 msg='op=PAM:setcred acct="postgres" exe="/bin/su" (hostname=?, addr=?, terminal=pts/0 res=success)'
Apr 26 15:31:35 secure kernel: type=1104 audit(1335465095.541:135): user pid=12344 uid=501 auid=0 subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 msg='op=PAM:setcred acct="username" exe="/bin/su" (hostname=?, addr=?, terminal=pts/0 res=success)'
Apr 26 15:31:35 secure kernel: type=1104 audit(1335465095.541:136): user pid=23058 uid=0 auid=0 subj=system_u:system_r:sshd_t:s0-s0:c0.c1023 msg='op=PAM:setcred acct="username" exe="/usr/sbin/sshd" (hostname=ip, addr=ip, terminal=ssh res=success)'
Apr 26 15:31:35 secure kernel: type=1104 audit(1335465095.541:137): user pid=20990 uid=0 auid=0 subj=system_u:system_r:sshd_t:s0-s0:c0.c1023 msg='op=PAM:setcred acct="username" exe="/usr/sbin/sshd" (hostname=ip, addr=ip, terminal=ssh res=success)'
Apr 26 15:31:35 secure kernel: type=1106 audit(1335465095.542:138): user pid=23058 uid=0 auid=0 subj=system_u:system_r:sshd_t:s0-s0:c0.c1023 msg='op=PAM:session_close acct="username" exe="/usr/sbin/sshd" (hostname=ip, addr=ip, terminal=ssh res=success)'
Apr 26 15:31:35 secure kernel: Kernel logging (proc) stopped.

Apr 26 16:13:09 secure kernel: imklog 3.14.1, log source = /proc/kmsg started.
Apr 26 16:13:09 secure kernel: Inspecting /boot/System.map-2.6.25-14.fc9.x86_64
Apr 26 16:13:09 secure kernel: Loaded 28121 symbols from /boot/System.map-2.6.25-14.fc9.x86_64.
Apr 26 16:13:09 secure kernel: Symbols match kernel version 2.6.25.
Apr 26 16:13:09 secure kernel: No module symbols loaded - kernel modules not enabled.
Apr 26 16:13:09 secure rsyslogd: [origin software="rsyslogd" swVersion="3.14.1" x-pid="2204" x-info="http://www.rsyslog.com"] restart
Apr 26 16:13:09 secure kernel: Initializing cgroup subsys cpuset
Apr 26 16:13:09 secure kernel: Initializing cgroup subsys cpu
Apr 26 16:13:09 secure kernel: Linux version 2.6.25-14.fc9.x86_64 (mockbuild@) (gcc version 4.3.0 20080428 (Red Hat 4.3.0-8) (GCC) ) #1 SMP Thu May 1 06:06:21 EDT 2008

******************************************
-- here is the part of cron log file that started only after the reboot
Apr 26 16:13:14 secure crond[2560]: (CRON) STARTUP (1.0)
Apr 26 16:13:14 secure crond[2560]: CRON: error in (/etc/crontab) problem is (bad username)
Apr 26 16:13:14 secure crond[2560]: CRON: error in (/etc/crontab) problem is (bad username)
Apr 26 16:13:14 secure crond[2560]: CRON: error in (/etc/crontab) problem is (bad username)
Apr 26 16:13:14 secure crond[2560]: CRON: error in (/etc/crontab) problem is (bad username)
Apr 26 16:13:14 secure anacron[2601]: Anacron 2.3 started on 2012-04-26
Apr 26 16:13:14 secure anacron[2601]: Will run job `cron.daily' in 65 min.
Apr 26 16:13:14 secure anacron[2601]: Jobs will be executed sequentially
Apr 26 17:18:14 secure anacron[2601]: Job `cron.daily' started