Customer Experience and Feedbacks With Mondorescue

mondoarchive on Red Hat/EL running BIND (/proc also mounted in chroot)

This is just a TIP from my observations on:
Red Hat/EL AS v4.4 running bind-9.2.4-16.EL4
It may hold true for other versions of Red Hat as well as Fedora.

The named (bind) runs in a chroot environment, and as part of its startup script there is a:

        mount --bind /proc /var/named/chroot/proc

which means (as described in man mount):

       Since Linux 2.4.0 it is possible to remount part of the file
       hierarchy somewhere else. The call is
              mount --bind olddir newdir
       After this call the same contents is accessible in two places.

As a result you have this (edited from df -ha):

Filesystem            Size  Used Avail Use% Mounted on
none                     0     0     0   -  /proc
/proc                    0     0     0   -  /var/named/chroot/proc

Yes, /proc is mounted in two places and there's no announcement to that effect -- it is not immediately obvious! You gotta look for it, and that extra mount is not automatically excluded by mondoarchive.

What this means is that if you mondoarchive the system without excluding that chroot area (/var/named/chroot/proc) you will be including it (/proc) in your backup.
(Or you could stop named and: umount /var/named/chroot/proc.)

In any case, the further gotcha is that if you get the /var/named/chroot/proc in the backup, it is going to be created when you boot/run mondorestore. If you booted the mondorestore (CD/DVD) for a system recovery, you need to keep in mind:

  • the named will not be running; therefore,
  • the startup script (/etc/init.d/named) will not have done the "mount --bind /proc /var/named/chroot/proc", which means
  • you will create that whole filesystem as real files/directories in /var/named/chroot/proc.

Of course, when the named startup script is run it should go ahead and do the "mount --bind" over the top of the junk, but stuff like that just makes me nervous.

ANYWAY, I just thought I'd drop this observation out there for whomever might be interested.

I suspect that such a thing might be the case on other stuff that runs in chroot jail. Maybe it is also true for other non-RH distributions, too?

Just something to be aware of.
The moral is: Check your mounts before you do your backup''

Bill R. Williams

ETSU Library Systems

January 2007