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diff --git a/nixos/doc/manual/configuration/sshfs-file-systems.section.md b/nixos/doc/manual/configuration/sshfs-file-systems.section.md new file mode 100644 index 00000000000..4625fce03d5 --- /dev/null +++ b/nixos/doc/manual/configuration/sshfs-file-systems.section.md @@ -0,0 +1,104 @@ +# 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 <package>sshfs</package>. +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 test-key +Your public key has been saved in test-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](options.html#opt-fileSystems) option. +Here's a typical setup: +```nix +{ + system.fsPackages = [ pkgs.sshfs ]; + + 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. +::: |