Configure a ZFS volume for Time Machine on NAS

Preparation

A ZFS pool should surely pre-exist there to allow for the operations introduced later.

• Key point: Why not split, or shrink existing volumes for a Time Machine volume?

  Not viable. A ZFS partition always tries to occupy as much space as possible, so does ZFS volumes under it, sharing the entire space of it. To reserving some space is exactly what the quota property is designed for.

  In addition, you can use the reservation property to guarantee that a specified amount of disk space is available to a file system. Both properties apply to the dataset on which they are set and all descendents of that dataset.

  More…

• Creating a new ZFS filesystem

  zfs create -o compression=lz4 pool/filesystem

  where the purpose of an optional argument -o compression=lz4 is to turn on the compression for this dataset.

  Check if it is mounted:

  zfs get mountpoint pool/filesystem

  zfs get mounted pool/filesystem

• Setting Quotas on ZFS File Systems

  zfs set quota=10G pool/dataset

  zfs get quota pool/dataset

  Check for any change in AVAIL:

  zfs list -r pool

• Grant access to ZFS volume

  The reading and writing permission controls of the ZFS volume simply go with that in the Linux filesystem:

  sudo chown owner:group pool/filesystem

Set up Time Machine Server

• Dependency installation

  sudo apt install netatalk avahi-daemon

• Netatalk Configuration

  # /etc/netatalk/afp.conf  
  
  [myTimeMachine]  
  path = /pool/dataset
  valid users = linux_user 
  time machine = yes  

  sudo systemctl restart netatalk.service

• Avahi Configuration

  Create file /etc/avahi/services/afpd.service as:

  <?xml version="1.0" standalone='no'?><!--*-nxml-*--> 
  <!DOCTYPE service-group SYSTEM "avahi-service.dtd"> 
  <service-group>  
  <name replace-wildcards="yes">%h</name>   
  <service> 
      <type>_afpovertcp._tcp</type> 
      <port>548</port> 
  </service>   
  <service> 
      <type>_device-info._tcp</type> 
      <port>0</port> 
      <txt-record>model=Xserve</txt-record> 
  </service>   
  </service-group>

  sudo systemctl restart avahi-daemon.service

• Unblock network access from firewalls

  Unblock afp protocol requests (example):

  sudo iptables -A INPUT -p tcp –dport afpovertcp -j ACCEPT

Usage

Press [Cmd]+[K] in Finder. Use the Linux user credential to log into afp://ip_address_or_domain_name.

References

Building NAS with ZFS, AFP/Samba for Time Machine

Netatalk Wiki

Mounting and Sharing ZFS File Systems

ZFS Quotas and Reservations