[CentOS] Mount --bind source / mountpoint out of sync

Mon Aug 22 17:01:33 UTC 2011
Trey Dockendorf <treydock at gmail.com>

I have a shared web server that users can SSH / SFTP into to access their
web content.  Each users home directory is in a change root, and I use
"mount -o bind" to put their respective webpage's document root into their
home directory.  Recently I was made aware that the contents of the mount's
source are not the same as the mount point's, which I don't see how that is
possible.

The file system is 3 virtual disks...each part of the same volume group.  I
have three LVMs, "/" , "/chroot" , and "/var".

Here's the entry in /etc/fstab...

/var/www/example.com   /chroot/home/user1/example.com   none
 defaults,bind   0   0

The mount is active, yet running a recursive diff between "/var/www/
example.com" and "/chroot/home/user1/example.com" shows numerous
differences.

Here's "mount" output
------------------
/dev/mapper/VolGroup00-LogVol00 on / type ext3 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/sda1 on /boot type ext3 (rw)
tmpfs on /dev/shm type tmpfs (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
/dev/mapper/VolGroup00-lv_chroot on /chroot type ext3 (rw)
/var/www/example.com on /chroot/home/user1/example.com type none (rw,bind)
/dev/mapper/VolGroup00-lv_var on /var type ext3 (rw)


I honestly have no idea how this is possible.  Is using "mount -o bind" not
the best method to give a chrooted user access to a single directory outside
the chroot?  Would it be better to leave the web root in the chroot and have
Apache (outside chroot) reference that location?

Thanks
- Trey
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