linux: how to roll a log file that is locked by another app?

Question

I'm using tomcat on redhat and it logs to a file called tomcat.out -- I want to keep a daily log of this file by renaming tomcat.out to something like tomcat_.out. Only problem is tomcat keeps a lock on this file so I can't rename it without breaking the log (tomcat stops logging to it). I tried using symlinks for it, but that failed too. any other ideas? what about named pipes (I don't know how to do that)...??

thanks in advance

Answer 1

Shut down the application that has it locked. There's a reason why applications lock files. When multiple writers exist for a single file, bad things happen, unless there's a complex real-time I/O management system to prevent conflicts (and that generally doesn't exist on Linux/UNIX systems).

Answer 2

would cp tomact.out tomact_.out work? or is this not at all what you're looking for? it would copy the file over to a new file, and shouldn't be restricted by tomcat. You could make a cron job to do it whenever you wanted.

Answer 3

Many servers e.g. httpd use SIGHUP to reread configs and reopen logfiles. Not sure about tomcat. Check the docs.

e.g. /etc/logrotate.d/httpd

/var/log/httpd/*log {

missingok

notifempty

sharedscripts

postrotate

/bin/kill -HUP `cat /var/run/httpd.pid 2>/dev/null` 2> /dev/null || true

endscript

}

Answer 4

I would use cp and cron to schedule a daily copy of it.