====== ZFS Snapshot Send/Receive ======

Local ZFS snapshots are uploaded to a remote server (backup) over SSH, using the utility znapzend to manage the snapshot schedule.

http://www.znapzend.org/

1. znapzend is installed as a deb package (systemd service) using: https://github.com/Gregy/znapzend-debian

2. Create a shared key for SSH to allow password-less login from source to dest server as the receiver backupuser

<note>
Do not specify a password on the shared key, just press enter when prompted.
</note>

<code>
ssh-keygen
ssh-copy-id -i /root/.ssh/id_rsa.pub root@destserver
</code>

3. Create the remote ZFS volume to receive the snapshots and delegate permissions to a non-root user.

<note>The ZFS volume of the given name must exist on the remote node
<code>*** WARNING: destination 'root@destserver:data/test' does not exist, will be ignored! ***</code></note>

<code>
destserver:~# zfs create data/test
</code>

<note>
'zfs allow' does not yet work with ZFS on Linux < 0.7.0 to allow a non-root destination user

<code>
destserver:~# zfs allow -u backupuser create,receive,rename,mount,send data/test

destserver:~# zfs allow data/test
---- Permissions on data/test ----------------------------------------
Local+Descendent permissions:
        user backupuser create,mount,receive,rename,send
</code>
</note>

3. Create a snapshot schedule consisting of a local SRC schedule, and the remote DST schedule to send the snapshots.

<note>
Keep snapshots for 1week, with a snapshot every 30 minutes
<code>
# znapzendzetup create SRC '1week=>30min' data/test DST '1week=>30min' root@destserver:data/test
</code>
</note>

Reload the config of the znapzend daemon
<code>
# systemctl reload znapzend.service
</code>

4. The backup schedule is saved as ZFS volume properties
<code>
# zfs get all data/test | grep org.znapzend
data/test  org.znapzend:tsformat       %Y-%m-%d-%H%M%S                         local
data/test  org.znapzend:pre_znap_cmd   off                                     local
data/test  org.znapzend:dst_0          root@destserver:data/test               local
data/test  org.znapzend:mbuffer        off                                     local
data/test  org.znapzend:dst_0_plan     1weeks=>30minutes                       local
data/test  org.znapzend:enabled        on                                      local
data/test  org.znapzend:zend_delay     0                                       local
data/test  org.znapzend:recursive      off                                     local
data/test  org.znapzend:mbuffer_size   1G                                      local
data/test  org.znapzend:post_znap_cmd  off                                     local
data/test  org.znapzend:src_plan       1weeks=>30minutes                       local
</code>

Watch the output of the znapzend daemon for any errors:
<code>
:~# journalctl -u znapzend.service -f &
</code>

Watch for local snapshots to be created:
<code>
# zfs list -t snap
NAME                                 USED  AVAIL  REFER  MOUNTPOINT
data/test@2017-08-27-110000             0      -   128K  -
</code>

<code>
destserver:~# zfs list -t snap
NAME                          USED  AVAIL  REFER  MOUNTPOINT
data/test@2017-08-27-110000      0      -    19K  -
</code>

<code>
~# znapzendztatz -r data/test
USED    LAST SNAPSHOT       DATASET
85.2K   2017-08-27-110000   data/test
    0   2017-08-27-110000   root@destserver:data/test
</code>

5. You can see how the files and directories looked at snapshot time by accessing the hidden .zfs directory
<code>
:~# find /data/test/.zfs -type f -ls
              7      1 -rw-r--r--   1 root     root            0 Aug 27 11:08 /data/test/.zfs/snapshot/2017-08-27-113000/a.txt
</code>

<code>
destserver:~# find /data/test/.zfs -type f -ls
              7      1 -rw-r--r--   1 root     root            0 Aug 27 14:08 /data/test/.zfs/snapshot/2017-08-27-113000/a.txt
</code>

<code>
:~# zfs diff data/test@2017-08-27-113000
M       /data/test/
M       /data/test/a.txt
+       /data/test/b.txt
</code>

<code>
:~# zfs diff data/test@2017-08-27-110000 data/test@2017-08-27-113000
M       /data/test/
+       /data/test/a.txt
</code>