If you’ve tried automatically mounting network shares on Linux during boot, you’ve likely run into a bunch of inconsistencies over the years - I know I have.

So I set out to find a robust way to do network mounting, without too many moving parts like e.g. NetworkManager.

The solution I’ve settled on involves fstab and Systemd, and whilst some still swear by SysVinit, the majority of large distros these days run Systemd out-of-the-box.

But wait I second, fstab already supports this, right? Well kinda, it has the old _netdev flag which still exists, and it is supposed to automatically wait for the network interface (NIC) to be up before attempting the mount.

That being said I’ve found it be very hit-and-miss on a bunch of different distros, and if the online forums are any indication to go by, I’m not alone.

So what’s the solution?

The solution is based around the fstab flag x-systemd.after, which instructs the mount to not happen until after something. That something in this solution is a custom service we’ll register with Systemd.

The service can be created with this command, which will create a file in the /etc/systemd/system/ folder called wait-for-nas.service. Make sure you adjust the IP to the target you want to mount - in this example it’s my NAS at 10.0.0.20.

sudo tee /etc/systemd/system/wait-for-nas.service <<EOF
[Unit]
Description=Blocks until it successfully pings 10.0.0.20
After=network-online.target

[Service]
ExecStartPre=/usr/bin/bash -c "while ! ping -c1 10.0.0.20; do sleep 1; done"
ExecStart=/usr/bin/bash -c "echo good to go"
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target
EOF

The service needs to have its rights adjusted like so: sudo chmod 644 /etc/systemd/system/wait-for-nas.service which makes it read/write for the owner, and read for everyone else.

Reload the service list: sudo systemctl daemon-reload

And you’re ready to enable the service: sudo systemctl enable wait-for-nas.service

What the service does is rather simple: It attempts to ping the IP, and will continue to try this every second until it eventually succeeds. Only when it succeeds in pinging it’ll change state to started. This way we’ll never attempt to mount the network share, without being able to reach it.

Finally add the lines you want to mount to your /etc/fstab file, similarly to this: //10.0.0.20/SHARE /home/USERNAME/SHARE cifs uid=USERNAME,gid=USERNAME,username=SHARE_USERNAME,password=SHARE_PASSWORD,iocharset=utf8,nobrl,x-systemd.after=wait-for-nas.service,vers=3.0 0 0

You’ll want to update the IP, as well as all uppercase words with your relevant options.

Do note the line above contains more than just our x-systemd.after flag, feel free to adjust the flags however you see fit.

If you’re curious here’s what each part does:

  • //10.0.0.20/SHARE: Remote path to mount
  • /home/USERNAME/SHARE: Local path to mount it to
  • cifs: Protocol used for mounting the network share, CIFS (aka. SMB these days) is the protocol used by Windows, and is often the default on NAS devices for wider client support. You could use NFS as well on Linux, but in most benchmarks I’ve seen CIFS/SMB actually comes out on top.
  • uid: username of your local linux user
  • gid: group of your local linux user (usually the same as your username)
  • username: username used to authenticate with the remote target
  • password: password used to authenticate with the remote target
  • iocharset: configures the encoding used for the network share, utf8 is a safe default that should for most people.
  • nobrl: disables sending byte range lock requests to the server. Without this LibreOffice has a tendency (at least for me) to screw up when attempting to save files.
  • x-systemd.after: We already covered this, it instructs the mount not to happen until after our service has started.
  • vers: Version of SMB to use, I’d recommend going with 3.0 if your remote target supports it.
  • 0 0: The first 0 indicates whether the file system should be “dumped” by the dump backup program (if installed), the second one is the order fsck should check the filesystem in. It can be 0 (don’t check) or 2 (check, after the root filesystem)