Zach
Schuermann

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RAID Time Machine on Linux

My main backup mechanism is a pair of Western Digital Red 2TB hard drives (arranged in RAID1) in my desktop at home. Since they are in RAID1, I only have 2TB of usable space but I can sustain a single drive failure. In order to backup to the RAID array, I've set up Time Machine over SMB to back up my Macbook and I've written a few other services to do things like backup my repositories on GitHub (work in progress).

Below, I'll go through how to set up a RAID array and run a container to expose a folder on the array as an SMB share for Time Machine backups. On my new machine with NixOS, I'm using the old AFP protocol (instead of SMB) running outside of a container. I've included an overview of my new setup on NixOS at the bottom, though much of the RAID setup is still pertinent.

Configure the raid array

Digital Ocean has a great article on setting up RAID arrays on Ubuntu. For my old Debian setup I roughly followed this guide. Here's what I did to erase my two disks (assigned at /dev/sdb and /dev/sdc), set up a RAID1 array (which I call /dev/md0), and format and mount the array at /raid.

BE WARNED: the instructions below will wipe both disks prior to setting up the array.

# get info and wipe free devices
$ lsblk -o NAME,SIZE,FSTYPE,TYPE,MOUNTPOINT
$ wipefs -a /dev/sdb # Did you read the warning above?
$ wipefs -a /dev/sdc # Did you read the warning above?

# create RAID1 array and verify
$ sudo mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sdb /dev/sdc
$ watch -d cat /proc/mdstat
$ sudo mdadm --detail --scan --verbose

# set up configs, format the array (ext4), and mount
$ sudo mdadm --detail --scan | sudo tee -a /etc/mdadm/mdadm.conf
$ cat /etc/mdadm/mdadm.conf
$ sudo update-initramfs -u
$ sudo mkfs.ext4 -F /dev/md0
$ sudo mkdir -p /raid
$ sudo mount /dev/md0 /raid

# verify
$ df -h -x devtmpfs -x tmpfs

# append to /etc/fstab to mount at every boot
$ echo '/dev/md0 /raid ext4 defaults,nofail,discard 0 0' | sudo tee -a /etc/fstab

# done!
$ lsblk
$ df -h

Run a Time Machine container

Now we can run Samba in a docker container to expose a folder (/raid/timemachine) on the RAID array as an SMB share. (See Docker's docs if you need to install Docker).

The one I've had luck with is https://github.com/mbentley/docker-timemachine, which allows you to run either Samba (SMB) or AFP (netatalk) and enable/disable Avahi discovery. Below is an example of using /raid/timemachine as a backup location for Samba without Avahi discovery.

$ mkdir -p /raid/timemachine
# time machine smb fileserver
$ docker run -d --restart=always \
  --name timemachine \
  --hostname timemachine \
  -p 137:137/udp \
  -p 138:138/udp \
  -p 139:139 \
  -p 445:445 \
  -e CUSTOM_SMB_CONF="false" \
  -e CUSTOM_USER="false" \
  -e DEBUG_LEVEL="1" \
  -e HIDE_SHARES="no" \
  -e EXTERNAL_CONF="" \
  -e MIMIC_MODEL="TimeCapsule8,119" \
  -e TM_USERNAME="timemachine" \
  -e TM_GROUPNAME="timemachine" \
  -e TM_UID="1000" \
  -e TM_GID="1000" \
  -e PASSWORD="<password>" \
  -e SET_PERMISSIONS="false" \
  -e SHARE_NAME="TimeMachine" \
  -e SMB_INHERIT_PERMISSIONS="no" \
  -e SMB_NFS_ACES="yes" \
  -e SMB_METADATA="stream" \
  -e SMB_PORT="445" \
  -e SMB_VFS_OBJECTS="acl_xattr fruit streams_xattr" \
  -e VOLUME_SIZE_LIMIT="0" \
  -e WORKGROUP="WORKGROUP" \
  -v /raid/timemachine:/opt/timemachine \
  -v timemachine-var-lib-samba:/var/lib/samba \
  -v timemachine-var-cache-samba:/var/cache/samba \
  -v timemachine-run-samba:/run/samba \
  mbentley/timemachine:smb

Start backups

On macOS, connect to the server with Finder (Finder > Go > Connect to Server…) and enter smb://<server-ip-address>. Then open System Preferences > Time Machine, and select the disk for backups.

NixOS