Linux – remount / move root folder to another partition on centos

Every linux filesystem (ext2, ext3, ext4, xfs, jfs, raiserfs) in current kernel can be frozen, but it must be placed on LVM first.

If you have LVM, making a snapshot automatically freezes the FS for the time it takes to make the snapshot -- it's better than doing only a freeze (your data is still available for writing and will not break the backup) and much better than simple rsync (as it will copy files in a consistent state).

Other questions:

XFS is safe, but can be problematic if you don't disable write cache or don't have battery backed cache (only ext3 is quite resilient to that)

Yes, ext4 is considered safe now. Choosing a FS mainly depends on the kind of workload you'll experience. XFS is slow with small files, very fast with large files.

You don't actually have to repartition your disk to accomplish this. An alternate solution is to use mount -o bind.

1. Stop all services running on the server, and confirm that there are no open handles to /var with lsof | grep /var - if there are, kill the processes holding them.
2. Unmount your 8GB drive (/var/www) and mount it somewhere else (e.g. /mnt)
3. On your 8GB disk, move the entire contents to a single folder - let's call it 'www'.
4. Move /var/ to your 8GB drive (you may want to copy and rename the original instead for a bit of safety) (So, you now have two folders /mnt/www and /mnt/var)
   • (Since /var/www is in var, it is simpler to just move it there at this point (i.e. mv /mnt/www /mnt/var/, although, I you should be able to setup nested mounts)
5. Mount bind /var: mount -o bind /mnt/var /var

6. Append to fstab:

   /mnt/var  /var    bind     defaults,noatime,bind        0   0

7. Check that everything is working, and resume normal operations

This approach should offer the same functionality, with a bit less risk (no repartitioning/resizing file systems) and more flexibility - if you want to add two or three more folders, you don't have to keep making new partitions.

As an aside, moving the entirety of /var to a second disk wouldn't be my first choice, I'd favour moving the directories that store data instead of those that store programs, such as the following: (you will probably find that /var/log and /var/lib use the majority of space in /var anyway).

• /var/log
• /var/lib/pgsql
• /var/spool/mail (and/or /var/vmail)
• /var/www (which you have already moved)

The same procedure can be applied to most directories (except something like /boot). Also, you may consider using rsync instead of cp, if some files are locked, etc. and you have to run it a second time, it can be more forgiving.