# Use systemd to mount filesystem

###### tag: `systemd` `linux`

Notes to use systemd mount unit.

#### mount local filesytem
create systemd file "/etc/systemd/system/mnt-data.mount". The unit filename must reflect to the mount point path. For example, path "/mnt/data" has unit filename "mnt-data.mount".

[Unit]
Description = mount /dev/sda to /mnt/data

[Mount]
What = /dev/sda
Where = /mnt/data
Type = ext4
Options = defaults

[Install]
WantedBy = local-fs.target

root@NUC10:~# systemctl start mnt-data.mount
root@NUC10:~# systemctl status mnt-data.mount
● mnt-data.mount - mount /dev/sda to /mnt/data
     Loaded: loaded (/etc/systemd/system/mnt-data.mount; disabled; vendor preset: enabled)
     Active: active (mounted) since Tue 2023-11-14 01:53:37 AEDT; 1s ago
      Where: /mnt/data
       What: /dev/sda
      Tasks: 0 (limit: 76507)
     Memory: 1004.0K
        CPU: 62ms
     CGroup: /system.slice/mnt-data.mount

Nov 14 01:53:37 NUC10 systemd[1]: Mounting mount /dev/sda to /mnt/data...
Nov 14 01:53:37 NUC10 systemd[1]: Mounted mount /dev/sda to /mnt/data.

root@NUC10:~# df -h
Filesystem      Size  Used Avail Use% Mounted on
tmpfs           6.3G  2.4M  6.3G   1% /run
/dev/nvme0n1p1  916G  539G  331G  62% /
tmpfs            32G     0   32G   0% /dev/shm
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
tmpfs            32G     0   32G   0% /run/qemu
tmpfs           6.3G  104K  6.3G   1% /run/user/1000
/dev/sda        1.8T  844G  897G  49% /mnt/data

https://www.freedesktop.org/software/systemd/man/latest/systemd.special.html#local-fs.target

> Note Notify system that new unit files by command `systemctl daemon-reload`

#### mount network filesystem (NFS)
/etc/systemd/system/mnt-nfs.mount

[Unit]
Description = Mount NFS volume

[Mount]
What = m900:/mnt/data
Where = /mnt/nfs
Type = nfs
Options = defaults

[Install]
WantedBy = multi-user.target

#### with automount (for mnt-nfs.mount)
/etc/systemd/system/mnt-nfs.automount

[Unit]
Description = Auto mount NFS volume

[Automount]
Where = /mnt/nfs

[Install]
WantedBy = multi-user.target

root@NUC10:/mnt# systemctl start mnt-nfs.automount
root@NUC10:/mnt# systemctl status mnt-nfs.automount
● mnt-nfs.automount - Auto mount NFS volume
     Loaded: loaded (/etc/systemd/system/mnt-nfs.automount; disabled; vendor preset: enabled)
     Active: active (waiting) since Tue 2023-11-14 12:01:07 AEDT; 5s ago
   Triggers: ● mnt-nfs.mount
      Where: /mnt/nfs

Nov 14 12:01:07 NUC10 systemd[1]: Set up automount Auto mount NFS volume.

root@NUC10:/mnt# df
Filesystem     1K-blocks      Used Available Use% Mounted on
tmpfs            6536248      2400   6533848   1% /run
/dev/nvme0n1p1 960302096 564538812 346908860  62% /
tmpfs           32681236         0  32681236   0% /dev/shm
tmpfs               5120         4      5116   1% /run/lock
tmpfs           32681236         0  32681236   0% /run/qemu
tmpfs            6536244       104   6536140   1% /run/user/1000
root@NUC10:/mnt# ls -l /mnt/nfs
total 8
drwxrwxrwx 4 root root 4096 Sep 25 01:30 bind9
drwxr-xr-x 5 root root 4096 Sep 22 01:49 gitlab
root@NUC10:/mnt# df
Filesystem     1K-blocks      Used Available Use% Mounted on
tmpfs            6536248      2400   6533848   1% /run
/dev/nvme0n1p1 960302096 564538812 346908860  62% /
tmpfs           32681236         0  32681236   0% /dev/shm
tmpfs               5120         4      5116   1% /run/lock
tmpfs           32681236         0  32681236   0% /run/qemu
tmpfs            6536244       104   6536140   1% /run/user/1000
m900:/mnt/data 960301056  36037632 875408384   4% /mnt/nfs

> automount is not to mount automatically at boot process, it mounts filesystem when mount point is accessed (on daemon).

> you need to have mount unit file created first.
> For each automount unit file a matching mount unit file (see systemd.mount(5) for details) must exist which is activated when the automount path is accessed.

#### Reference
https://blog.csdn.net/seaship/article/details/116237747
https://forum.manjaro.org/t/root-tip-how-to-systemd-mount-unit-samples/1191
https://unix.stackexchange.com/questions/283442/systemd-mount-fails-where-setting-doesnt-match-unit-name
https://unix.stackexchange.com/questions/570958/mount-vs-automount-systemd-units-which-one-to-use-for-what