If your partition are not LVM Logical-Volumes, you can’t make a snapshot. If the
partition are not used, it’s recommended to remount it as read-only, with the
mount -o remount,ro /dev/xxx
If the partition cannot be remounted read-only (which is the case of the root
filesystem in general), it’s still possible to use fsarchiver to make a backup,
but you will have to take extra care. By default, fsarchiver complains if you
try to save a filesystem which is mounted in read-write mode. This is because
in cannot guarantee that the data will be consistent because files may change
during the backup of the filesystem. This is the reason why it shows the
following error message, and stops:
# fsarchiver savefs /mnt/archives/gentoo-backup-20090328-01.fsa /dev/sda2 -v
create.c#0642,filesystem_mount_partition(): partition [/dev/sda2] is mounted read/write.
please mount it read-only and then try again. you can do "mount -o remount,ro /dev/sda2".
you can also run fsarchiver with option '-A' if you know what you are doing.
When a filesystem is writeable during the backup, it means changes can be done
in files during that time, and there may be inconsistencies in the data. For
instance, if you are backing up a web server which is running both Apache and
Mysql, the Mysql database refers to files that can be uploaded in the Apache
directory from the website. In that case the backup could contains a reference
in the database but not the referred file because these files have been backed
up already. So you have to know whether or not your system may have such
If there is no risk of inconsistency, then you can use fsarchiver with option
-A to continue the backup of a filesystem which is mounted in read-write mode.