103 lines
4.0 KiB
Markdown
103 lines
4.0 KiB
Markdown
# SSHFS File Systems {#sec-sshfs-file-systems}
|
|
|
|
[SSHFS][sshfs] is a [FUSE][fuse] filesystem that allows easy access to directories on a remote machine using the SSH File Transfer Protocol (SFTP).
|
|
It means that if you have SSH access to a machine, no additional setup is needed to mount a directory.
|
|
|
|
[sshfs]: https://github.com/libfuse/sshfs
|
|
[fuse]: https://en.wikipedia.org/wiki/Filesystem_in_Userspace
|
|
|
|
## Interactive mounting {#sec-sshfs-interactive}
|
|
|
|
In NixOS, SSHFS is packaged as `sshfs`.
|
|
Once installed, mounting a directory interactively is simple as running:
|
|
```ShellSession
|
|
$ sshfs my-user@example.com:/my-dir /mnt/my-dir
|
|
```
|
|
Like any other FUSE file system, the directory is unmounted using:
|
|
```ShellSession
|
|
$ fusermount -u /mnt/my-dir
|
|
```
|
|
|
|
## Non-interactive mounting {#sec-sshfs-non-interactive}
|
|
|
|
Mounting non-interactively requires some precautions because `sshfs` will run at boot and under a different user (root).
|
|
For obvious reason, you can't input a password, so public key authentication using an unencrypted key is needed.
|
|
To create a new key without a passphrase you can do:
|
|
```ShellSession
|
|
$ ssh-keygen -t ed25519 -P '' -f example-key
|
|
Generating public/private ed25519 key pair.
|
|
Your identification has been saved in example-key
|
|
Your public key has been saved in example-key.pub
|
|
The key fingerprint is:
|
|
SHA256:yjxl3UbTn31fLWeyLYTAKYJPRmzknjQZoyG8gSNEoIE my-user@workstation
|
|
```
|
|
To keep the key safe, change the ownership to `root:root` and make sure the permissions are `600`:
|
|
OpenSSH normally refuses to use the key if it's not well-protected.
|
|
|
|
The file system can be configured in NixOS via the usual [fileSystems](#opt-fileSystems) option.
|
|
Here's a typical setup:
|
|
```nix
|
|
{
|
|
fileSystems."/mnt/my-dir" = {
|
|
device = "my-user@example.com:/my-dir/";
|
|
fsType = "sshfs";
|
|
options =
|
|
[ # Filesystem options
|
|
"allow_other" # for non-root access
|
|
"_netdev" # this is a network fs
|
|
"x-systemd.automount" # mount on demand
|
|
|
|
# SSH options
|
|
"reconnect" # handle connection drops
|
|
"ServerAliveInterval=15" # keep connections alive
|
|
"IdentityFile=/var/secrets/example-key"
|
|
];
|
|
};
|
|
}
|
|
```
|
|
More options from `ssh_config(5)` can be given as well, for example you can change the default SSH port or specify a jump proxy:
|
|
```nix
|
|
{
|
|
options =
|
|
[ "ProxyJump=bastion@example.com"
|
|
"Port=22"
|
|
];
|
|
}
|
|
```
|
|
It's also possible to change the `ssh` command used by SSHFS to connect to the server.
|
|
For example:
|
|
```nix
|
|
{
|
|
options =
|
|
[ (builtins.replaceStrings [" "] ["\\040"]
|
|
"ssh_command=${pkgs.openssh}/bin/ssh -v -L 8080:localhost:80")
|
|
];
|
|
|
|
}
|
|
```
|
|
|
|
::: {.note}
|
|
The escaping of spaces is needed because every option is written to the `/etc/fstab` file, which is a space-separated table.
|
|
:::
|
|
|
|
### Troubleshooting {#sec-sshfs-troubleshooting}
|
|
|
|
If you're having a hard time figuring out why mounting is failing, you can add the option `"debug"`.
|
|
This enables a verbose log in SSHFS that you can access via:
|
|
```ShellSession
|
|
$ journalctl -u $(systemd-escape -p /mnt/my-dir/).mount
|
|
Jun 22 11:41:18 workstation mount[87790]: SSHFS version 3.7.1
|
|
Jun 22 11:41:18 workstation mount[87793]: executing <ssh> <-x> <-a> <-oClearAllForwardings=yes> <-oServerAliveInterval=15> <-oIdentityFile=/var/secrets/wrong-key> <-2> <my-user@example.com> <-s> <sftp>
|
|
Jun 22 11:41:19 workstation mount[87793]: my-user@example.com: Permission denied (publickey).
|
|
Jun 22 11:41:19 workstation mount[87790]: read: Connection reset by peer
|
|
Jun 22 11:41:19 workstation systemd[1]: mnt-my\x2ddir.mount: Mount process exited, code=exited, status=1/FAILURE
|
|
Jun 22 11:41:19 workstation systemd[1]: mnt-my\x2ddir.mount: Failed with result 'exit-code'.
|
|
Jun 22 11:41:19 workstation systemd[1]: Failed to mount /mnt/my-dir.
|
|
Jun 22 11:41:19 workstation systemd[1]: mnt-my\x2ddir.mount: Consumed 54ms CPU time, received 2.3K IP traffic, sent 2.7K IP traffic.
|
|
```
|
|
|
|
::: {.note}
|
|
If the mount point contains special characters it needs to be escaped using `systemd-escape`.
|
|
This is due to the way systemd converts paths into unit names.
|
|
:::
|