Changes between Version 1 and Version 2 of CustomerExperience


Ignore:
Timestamp:
Jan 23, 2007, 5:49:02 PM (13 years ago)
Author:
Bill R. Williams
Comment:

--

Legend:

Unmodified
Added
Removed
Modified
  • CustomerExperience

    v1 v2  
    11== Customer Experience and Feedbacks With Mondorescue ==
     2
     3== {{{mondoarchive}}} on Red Hat/EL running BIND ({{{/proc}}} also mounted in chroot) ==
     4
     5This is just a TIP from my observations on:[[BR]]
     6Red Hat/EL AS v4.4 running bind-9.2.4-16.EL4[[BR]]
     7It may hold true for other versions of Red Hat as well as Fedora.
     8
     9The {{{named}}} (bind) runs in a ''chroot'' environment, and as part of its
     10startup script there is a:
     11{{{
     12        mount --bind /proc /var/named/chroot/proc
     13}}}
     14which means (as described in man mount):
     15{{{
     16       Since Linux 2.4.0 it is possible to remount part of the file
     17       hierarchy somewhere else. The call is
     18              mount --bind olddir newdir
     19       After this call the same contents is accessible in two places.
     20}}}
     21As a result you have this (edited from {{{df -ha}}}):
     22{{{
     23Filesystem            Size  Used Avail Use% Mounted on
     24...[snip]...
     25none                     0     0     0   -  /proc
     26...[snip]...
     27/proc                    0     0     0   -  /var/named/chroot/proc
     28...[snip]...
     29}}}
     30
     31Yes, {{{/proc}}} is mounted in two places, and there's no announcement to
     32that effect -- it is not immediately obvious!  You gotta look for it.
     33And that extra mount is not automatically excluded by {{{mondoarchive}}}.
     34
     35What this means is that if you {{{mondoarchive}}} the system without
     36excluding that chroot area ({{{/var/named/chroot/proc}}}) you will be
     37including it ({{{/proc}}}) in your backup.
     38[[BR]]
     39(Or you could stop named and: {{{umount /var/named/chroot/proc}}}.)
     40
     41In any case, the further gotcha is that if you get the
     42{{{/var/named/chroot/proc}}} in the backup, it's going to be created when
     43you boot/run {{{mondorestore}}}.
     44If you booted the {{{mondorestore}}} (CD/DVD) for a system
     45recovery, you need to keep in mind:
     46 * the {{{named}}} will not be running; therefore,
     47 * the startup script ({{{/etc/init.d/named}}}) will ''not'' have done the "{{{mount --bind /proc /var/named/chroot/proc}}}", which means
     48 * you will create that whole filesystem as ''real'' files/directories in {{{/var/named/chroot/proc}}}. 
     49[[BR]]
     50Of course, when the
     51{{{named}}} startup script is run it should go ahead and do the
     52"{{{mount --bind}}}"
     53over the top of the junk, but stuff like that just makes me
     54nervous.
     55
     56''ANYWAY'', I just thought I'd drop this observation out there for
     57whomever might be interested.
     58
     59I suspect that such a thing might be the case on other stuff that runs
     60in chroot jail.  Maybe it is also true for other non-RH distributions,
     61too?
     62
     63Just something to be aware of.
     64[[BR]]
     65The moral is:
     66''Check your mounts before you do your backup!''
     67