Tim's blah blah blah

Timemachine to Linux Server

(Updated: )

Here I document my setup of networked Time Machine backups to my linux server over Samba (SMB), which should be faster than AFS (photographylife.com). The data is stored on a USB disk connected to the server formatted with zfs.

Ideally I would be able to backup over network, and unplug the disk from the server to directly restore from it, however the networked Time Machine backup is of different structure than a backup to a directly connected disk, so that’s still on the wishlist.



  1. Prepare disk
    1. Install ZFS on Ubuntu (ubuntu.com)
    2. Partition disk (linuxhint.com) – NB ensure you use static labels (archlinux.org) or else your pools might disappear (benjaminrampe.de)! (If they did disappear, you debug sudo zdb, search sudo zpool import and import them again (stackexchange.com): zpool import -d /dev/disk/by-id <pool-name>)
      parted /dev/disk/by-id/
      mklabel GPT
    3. Create pool sudo zpool create pool0 /dev/disk/by-id/
    4. Create datasets (arstechnica.com)
      sudo zfs create pool0/timemachinembp
      sudo zfs set quota=1200G pool0/timemachinembp
      sudo zfs create pool0/timemachinemba
      sudo zfs set quota=300G pool0/timemachinemba
      zfs list
    5. Automatic spin-down of USB disk (openmediavault.org) (old hd-idle (sourceforge.net), new hd-idle (github.com)), run at reboot from crontab, tell logrotate we want the log files to rotate.
      sudo hd-idle -t disk/by-id/wwn-0x3e41415851524c4a # optionally test once
      1. Either run via system service
        cat << EOF | sudo tee --append /etc/default/hd-idle
        # TvW 20210313 Setting up hd-idle for USB disk
        HD_IDLE_OPTS="-i 0 -a disk/by-id/wwn-0x3e41415851524c4a -i 3600 -l /var/log/hd-idle.log"
        sudo service hd-idle start
        grep hd-idle /var/log/syslog
      2. Or run via crontab
        (sudo crontab -l 2>/dev/null; echo "@reboot hd-idle -a disk/by-id/wwn-0x3e41415851524c4a -i 3600 -l /var/log/hd-idle.log";) | sudo crontab -
      3. In both cases, set-up logrotate for hd-idle:
        cat << EOF | sudo tee /etc/logrotate.d/hd-idle
        /var/log/hd-idle.log {
  2. Create backup users
    1. No new homedir, point to datasets instead. Don’t allow shell login. No password needed on system level.
      sudo useradd --no-create-home --home-dir /pool0/timemachinembp --shell /usr/sbin/nologin backupmbp
      sudo useradd --no-create-home --home-dir /pool0/timemachinemba --shell /usr/sbin/nologin backupmba
    2. Set zfs dataset permissions & umask
      sudo chown backupmbp:backupmbp /pool0/timemachinembp
      sudo chown backupmba:backupmba /pool0/timemachinemba
      sudo chmod o-rx /pool0/timemachine{mbp,mba}
  3. Set-up file server using Samba v3 (photographylife.com)
    1. Install Samba >4.8.0 (kirb.me) for file serving and avahi-daemon for discovery sudo apt install samba avahi-daemon
    2. Allow users
      openssl rand -base64 20
      sudo smbpasswd -a backupmbp
      sudo smbpasswd -e backupmbp
      openssl rand -base64 20
      sudo smbpasswd -a backupmba
      sudo smbpasswd -e backupmba
    3. Configure Samba in /etc/samba/smb.conf:
          comment = Time Machine MBP
          path = /pool0/timemachinembp
          valid users = backupmbp
          browseable = yes
          writeable = yes
          create mask = 0600
          directory mask = 0700
          spotlight = yes
          vfs objects = catia fruit streams_xattr
          fruit:aapl = yes
          fruit:time machine = yes
          comment = Time Machine MBA
          path = /pool0/timemachinemba
          valid users = backupmba
          browseable = yes
          writeable = yes
          create mask = 0600
          directory mask = 0700
          spotlight = yes
          vfs objects = catia fruit streams_xattr
          fruit:aapl = yes
          fruit:time machine = yes
    4. Disable printing (serverfault.com) (because we don’t serve printers)
      load printers = no
      printing = bsd
      printcap name = /dev/null
      disable spoolss = yes
    5. Restart Samba and check if all OK
      sudo systemctl restart smbd
      tail -n 50 /var/log/samba/log.smbd
      should show
      daemon_ready: daemon 'smbd' finished starting up and ready to serve connections
    6. Check if stuff is working with sudo smbstatus, check users known to samba with sudo pdbedit -L -v (from stack (askubuntu.com))
  4. Debugging zfs in case something goes wrong, I still don’t really get how zfs works :p. Also see here (askubuntu.com).
    zpool status
    sudo zpool import -c /etc/zfs/zpool.cache
    sudo zpool import <id>
    sudo zpool import pool0
    sudo zpool status
    sudo zfs umount pool0
    1. See also https://superuser.com/questions/685882/zpool-pool-i-o-is-currently-suspended (superuser.com)

Configuration on Mac

Based on this (kirb.me) this (macworld.com) and this (lifehacker.com) guides.

  1. Create sparse encrypted disk image using Disk Utility on network (Samba) share, naming as NAME_MACADDRESS.sparsebundle (NAME from scutil --get ComputerName and MACADDRESS from ifconfig en0 | grep ether sans colons), with fixed size to constrain Time Machine disk use.
  2. Mount said disk image, store password in Keychain to allow MacOS Time Machine to mount/unmount by itself (maybe this is not necessary)
  3. Tell Time Machine to use the network volume: sudo tmutil setdestination -a /Volumes/{network-drive}
  4. Enter network share credentials & disk image password

If you accidentally delete the Time Machine destination

  1. Tell Time Machine to use the network volume again: sudo tmutil setdestination -a /Volumes/{network-drive}
  2. Tell Time Machine to use the existing backup.