Editing VPS Management (section)

== Problems with `find` ==

There was a bug in the FreeBSD vn-filesystem code.  The bug causes the system to crash or hang when someone runs the `find` command inside their vn-backed filesystem (and even though the bug may have been fixed, due to the i/o overhead, we still don't like find).

Now, this does not always happen - however, any jail machine with more than 20 systems on it will crash every night if every system on it runs the daily periodic script out of their crontab, and updates their locate database with the find command.

(the locate database is a small, FreeBSD specific database that is populated nightly from a cron job, and is then used to provide fast answers to the `locate` command)

In normal systems (32-40 jails on them), all that has to be done is make sure nobody runs the daily periodic.  This means that the file /etc/crontab, instead of looking like this:

<pre># do daily/weekly/monthly maintenance
1      3       *       *       *       root    periodic daily
15     4       *       *       6       root    periodic weekly
30     5       1       *       *       root    periodic monthly</pre>

Needs to look like this:

<pre># DO NOT UNCOMMENT THESE - contact support@johncompanies.com for details
#1      3       *       *       *       root    periodic daily
#15     4       *       *       6       root    periodic weekly
#30     5       1       *       *       root    periodic monthly
## DO NOT UNCOMMENT THESE ^^^^^^^^</pre>

and the problem will generally not occur at all.  New filesystem images are always altered in this way, so all systems are set like this.

However, if you have enough systems running, even casual uses of find, outside of the periodic scripts, can cause the system to crash.  We are seeing this on jail13, which crashes about once per week.

There is not yet any resolution to this problem.

So, if you have a freebsd system crash, see if anyone has uncommented their daily periodic line - you can see them for everyone by running:

 /bin/sh

and then running:

<pre>for f in `df -k | grep vn | awk '{print $6}'` ; do echo `cat $f/etc/crontab | grep "periodic daily"` $f ; done | more</pre>

(all one line, one command)

And then edit those /etc/crontabs and comment them out again.