continuous display of log files (better tail -f)

All good sysadmins know about using tail -f to follow a log file. I use this all the time to follow /var/log/messages and my gluster logs in particular. Maybe everyone already knows this, but it deserves a PSA: after a certain amount of time (~days) it seems that new messages don’t appear!

What happens by default is that tail -f follows the file descriptor, not the file name, so when your log files get rotated, the file descriptor still points to the (now renamed) file which no longer gets updates any more.

The solution is to get tail to follow the file name you’re interested in:

tail --follow=name /var/log/messages

EDIT: Fortunately there is a shorter way of running this too, you can use:

tail -F

on any up to date version of tail to get the same result. This adds in –retry to the –folllow=name argument.

Happy hacking!

James

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November 18, 2012
209 words

• technical