zfsync

remote ZFS replication made easy

Using ZFS opens up the really cool possibility to send snapshots to remote ZFS enabled servers, but managing synchronization of your snapshots can turn out more difficult. zfsync makes keeping these snapshots in sync easy.

It offers a purely in shell written script, and works without any dependencies on FreeBSD and *Solaris systems.

##TL;DR:

zfsync -H remote.host -T tank/backups/myhost zroot/precious/data

syncs all filesystems from zroot/precious/data to the remote host.

##Usage:

zfsync [-dhiPq] [-U target_user] [-I identity_file] [-k retention]
       [-K retention] -H target_host -T target_zfs
       source_zfs

    source_zfs is the filesystem that should be synced to a remote host

Options:
    -d                   enable debugging (negates -q)
    -B                   even when mbuffer is detected, don't buffer
    -h                   show you this help page
    -H target_host       host to send snapshots to [required]
    -i                   send incremental stream between local and remote
                         snapshot instead of a stream package of all
                         intermediary snapshots
    -I identity_file     use this key for authentication
    -k local_retention   after synchronizing, apply local retention
    -K remote_retention  after synchronizing, apply remote retention
    -P                   do not set user properties on remote end
    -q                   be more quiet
    -T target_zfs        ZFS on target host to send snapshots to [required]
    -U target_user       alternative user to authenticate as on remote host

##Preparing remote host

Currently, zfsync should just work as long as the remote host is running FreeBSD or *Solaris and you have access to it over SSH. While it is certainly possible, you really shouldn't use the root user for receiving the ZFS snapshots (arguably for no SSH access at all, actually). Instead, set up a non-privileged user, most preferably with public key access, on the remote host. Here is a FreeBSD example:

remote host:

pw useradd -n zfsync -d /home/zfsync -m -w random -s /bin/sh
mkdir ~zfsync/.ssh/
ssh-keygen -f ~zfsync/.ssh/id_rsa
chown -R zfsync ~zfsync/.ssh
zfs allow -u zfsync create,mount,receive tank/backups/myhost

to create non-privileged user zfsync, set up a public/private key and give user zfsync minimal permissions for receiving ZFS snapshots tank/backups/myhost (zfsync will warn you otherwise). The public key ~zfsync/.ssh/id_rsa.pub should be copied to the source host via a secure channel, so it could be pointed to with -I while using -U zfsync on the next sync. You should add a strong passphrase to the key file, and use ssh-agent so you can cron syncing your filesystems. If you want to keep remote retention, make sure user zfsync has destroy permissions as well on the remote filesystem.

##Known issues

• has to be tested on GNU/Linux with ZFSOnLinux
• zfsync does not support multiple source_zfs arguments yet
• on *Solaris, /bin/sh is symlinked to ksh on some systems, which breaks zfsync