dsnap-sync/usr/share/doc/Examples.md

Examples

Automounter

dsnap-sync will take advantage of systemd automount units to incorporate external, removable disks into the selection process for target devices.

btrfs disk

Format the disk with btrfs tools to prepare it as a target. The following example will reference to a btrfs disk and mount a given subvolume.

systemd automount units

mount unit: var-backups-archive\x2ddisk1.mount

[Unit]
Description=Backup - Archiv-Disk 1
Documentation=man:systemd.mount(5) man:mount.btrfs(8)
DefaultDependencies=yes

[Mount]
What=UUID=977b4ecf-be67-4643-84f5-10b368c24d25
Where=/var/backups/archive-disk1
Type=btrfs
Options=defaults,subvol=@archive-disk1,compress=lzo

[Install]
WantedBy=multi-user.target

automount unit: var-backups-archive\x2ddisk1.automount

[Unit]
Description=Automount Backup - Archive-Disk 1
Documentation=man:systemd.automount(5)

[Automount]
Where=/var/backups/archive-disk1
TimeoutIdleSec=45

[Install]
WantedBy=multi-user.target

dsnap-sync command line usage

backup to local target

Default: no selections, run for all snapper configs

# dsnap-sync

Default: Select two configs, the backupdir and verbose output

# dsnap-sync --verbose --config root --config data2 --backupdir=toshiba_r700

Dry-run: Select config, select Target, as batchjob (--noconfirm)

# dsnap-sync -c root -s 265 --noconfirm --dry-run

backup to remote target

dsnap-sync will rely on ssh access to the target host. For batch usage make sure, that your public key is accepted for a remote login as user 'root'. You may have to adapt /root/.ssh/authorized_keys on the target host.

On your target host, you should also verify the availability of a dsnap-sync config-template for snapper. A template dsnap-sync is included in the package for your convenience.

Dryrun: Select remote host <ip/fqdn>, interactive, run for all configs

dsnap-sync --dry-run --remote <fqdn/ip>
Select target disk...
   0) /var/lib/snap-sync (uuid=b5915f47-38a8-4b37-8de6-c8b15d9aba5a,subvolid=257,subvol=/var/lib/@snap-sync)
   1) /var/backups/archive-disk4 (uuid=137b4a36-6e17-487b-a328-29b0d1e020c3,subvolid=257,subvol=/@dws-archive-disk4)
   2) /var/backups/archive-disk3 (uuid=c9fcbfd3-6a1f-4b43-8176-b6f326bf46c7,subvolid=257,subvol=/@dws-archive-disk3)
   3) /var/backups/archive-disk1 (uuid=977b4ecf-be67-4643-84f5-10b368c24d25,subvolid=257,subvol=/@dws-archive-disk1)
   4) /var/backups/archive-disk2 (uuid=b68c8a31-9878-4ec1-b7ed-948de2125285,subvolid=257,subvol=/@dws-archive-disk2)
   x) Exit
Enter a number: 1

Dry-run with given Target for snapper config 'data2', no confirmations

Sync: Select config 'data2', remote host <ip/fqdn>, target '/var/lib/snap-sync', as batchjob (--noconfirm)

# dsnap-sync --config data2 --remote <fqdn/ip> --target /var/lib/snap-sync --batch --verbose

systemd

dsnap-sync will structure all scheduling tasks while using systemd units. To perform a backup process for just a single snapper configuration at a given time, you have to define a pair of a systemd service unit and a corresponding systemd timer unit.

Below we define a generic dsnap-sync service unit that should be located at /etc/systemd/system. Following call will reference this template:

systemd enable dsnap-sync@data2.service

service unit: `dsnap-sync@.service

[Unit]
Description=dsnap-sync backup for target %i

[Install]
WantedBy=multi-user.target

[Service]
Type=simple
ExecStart=/usr/bin/dsnap-sync \
           --config %i \
           --uuid 7360922b-c916-4d9f-a670-67fe0b91143c \
		   --subvolid 5 \
		   --remote backup-host
		   --batch

overriding service unit: dsnap-sync@data2.service

Please remember, that the template example encode a given target UUID and SUBVOLID. If you want the unit to serve individual parameter, you have to override the it like:

systemd edit dsnap-sync@data2.service

Define a service paragraph, clean out the ExecStart= parameter and refine a new ExedStart= parameter with the intended.

[Service]
ExecStart=
ExecStart=/usr/bin/dsnap-sync \
           --config %i \
           --target /var/lib/dsnap-sync \
		   --remote my-backup-host
		   --batch

timer unit: dsnap-sync@.timer

Below we define a generic dsnap-sync timer unit that should be located at /etc/systemd/system.

[Unit]
Description=dsnap-sync weekly backup

[Timer]
OnCalendar=weekly
AccuracySec=12h
Persistent=true

[Install]
WantedBy=timers.target

Following call will reference this template:

systemd enable dsnap-sync@data2.timer

snapper extensions

For any new dsnap-sync btrfs-snapshot a new target snapper structure is need, if the target backups should be managable via snapper.

dsnap-sync will create this structure as needed. During the creation it will reference to a template called dsnap-sync. Please adapt it if your milage varies.

dsnap-sync template

###
# snapper template for dsnap-sync handling
###

# subvolume to snapshot
SUBVOLUME="/var/lib/dsnap-sync"

# filesystem type
FSTYPE="btrfs"


# users and groups allowed to work with config
ALLOW_USERS=""
ALLOW_GROUPS="adm"

# sync users and groups from ALLOW_USERS and ALLOW_GROUPS to .snapshots
# directory
SYNC_ACL="yes"


# start comparing pre- and post-snapshot in background after creating
# post-snapshot
BACKGROUND_COMPARISON="yes"


# handele NUMBER_CLEANUP via systemd, if a timer unit is active
NUMBER_CLEANUP="yes"

# limit for number cleanup
NUMBER_MIN_AGE="1800"
NUMBER_LIMIT="52"
NUMBER_LIMIT_IMPORTANT="12"

# handle TIMELINE via systemd, if a timer unit is active
TIMELINE_CREATE="yes"

# create a systemd.timer unit to handle TIMELINE cleanup
TIMELINE_CLEANUP="yes"

# timeline settings
TIMELINE_MIN_AGE="1800"
TIMELINE_LIMIT_HOURLY="1"
TIMELINE_LIMIT_DAILY="14"
TIMELINE_LIMIT_MONTHLY="11"
TIMELINE_LIMIT_YEARLY="2"


# cleanup empty pre-post-pairs
EMPTY_PRE_POST_CLEANUP="yes"

# limits for empty pre-post-pair cleanup
EMPTY_PRE_POST_MIN_AGE="1800"

# uncomment to exclude this subvol when calling
# snap-sync as timer unit
# SNAP_SYNC_EXCLUDE="yes"

# Valid CONFIG_TYPE: archive, child, parent
# CONFIG_TYPE="archive" -> if synced, stream snapshot to a non btrfs filesystem
# CONFIG_TYPE="child"   -> if synced, stream snapshot to a given CHILD_CONFIG name
CONFIG_TYPE="child"
#CHILD_CONFIG=<child config name>
#PARENT_CONFIG=<parent config name>