Ploop/Backup

How backup via snapshot is done

This article explains how to do consistent backups for ploop containers, using ploop snapshot feature.

Backup types

There are two ways of doing backups, both have their pros and cons.

• When doing an image backup, one copies ploop image files directly. There can be only one big file, or maybe a few relatively big files. Copying a few big files (rather than a lot of small files) is faster because there's not too much metadata (file info) to be copied). Also, filesystem properties are fully preserving (since images containing the filesystem are copied).

• When doing a file backup, one copies individual container' files. This is more suitable if you want selective backups (such as only some directories/files).

The following table summarizes pros and cons of both approaches.

Characteristic	Image	File
Incremental backups	Yes	Yes/No*
Selective backups	No	Yes
Faster full backup and restore	Yes	No
Preserve filesystem properties	Yes	No
Compatible with pre-ploop backups	No	Yes
Restore individual files	Yes	Yes

Image-based backup

Assuming you have a running container identified by $CTID. The following needs to be done:

# Known snapshot ID
ID=$(uuidgen)
VE_PRIVATE=$(VEID=$CTID; source /etc/vz/vz.conf; source /etc/vz/conf/$CTID.conf; echo $VE_PRIVATE)

# Take a snapshot without suspending a CT and saving its config
vzctl snapshot $CTID --id $ID --skip-suspend --skip-config

# Perform a backup using your favorite backup tool
# (cp is just an example)
cp $VE_PRIVATE/root.hdd/* /backup/destination

# Delete (merge) the snapshot
vzctl snapshot-delete $CTID --id $ID

File-based backup

Assuming you have a running container identified by $CTID. The following needs to be done:

# Known snapshot ID
ID=$(uuidgen)

# Directory used to mount a snapshot
MNTDIR=./mnt
mkdir $MNTDIR

# Take a snapshot without suspending a CT and saving its config
vzctl snapshot $CTID --id $ID --skip-suspend --skip-config

# Mount the snapshot taken
vzctl snapshot-mount $CTID --id $ID --target $MNTDIR

# Perform a backup using your favorite backup tool
# (tar is just an example)
tar cf backup.tar.xz $MNTDIR

# Unmount the snapshot
vzctl snapshot-umount $CTID --id $ID

# Delete (merge) the snapshot
vzctl snapshot-delete $CTID --id $ID

See also

• vzctl(8), section Snapshotting.