Mount Remote Directories with SSHFS on Linux and Configure Auto-mount at Boot

Introduction and Advantages of SSHFS

SSHFS (SSH Filesystem) is a user-space filesystem based on the SSH protocol. It allows you to mount a remote directory locally, enabling you to work with remote files as if they were local. Since it uses the encrypted SSH protocol for data transfer, it provides a high level of security.

Key advantages include:

• Convenience: No need to manually download, edit, and upload files. You can read and write directly at the local mount point, and changes are automatically synchronized to the remote host.
• High Security: Leverages the security mechanisms of the SSH protocol, ensuring encrypted data transmission.
• Wide Applicability: Useful for extending local storage (e.g., website attachment directories), cross-server file sharing, and synchronizing development environments.

Installation and Prerequisites

Before you begin, ensure the following conditions are met:

1. Both the local and remote hosts have an SSH service (like OpenSSH) installed.
2. The local system has the FUSE (Filesystem in Userspace) kernel module loaded. Check with:

lsmod | grep fuse

If there is no output, install the fuse module (e.g., on Ubuntu: sudo apt install fuse).

Install SSHFS:

• Debian/Ubuntu: sudo apt install sshfs
• RHEL/CentOS: sudo yum install fuse-sshfs or sudo dnf install fuse-sshfs
• If not available in your repository, you can compile from source on GitHub.

Manual Mounting and Unmounting

Mounting a Remote Directory

First, create a local mount point:

sudo mkdir /mnt/remote

Then use sshfs to mount the remote directory (example uses remote user 'user', IP '111.111.111.111', and remote directory '/home'):

sshfs -o allow_other [email protected]:/home /mnt/remote

The -o allow_other option allows other users to access the mount point. You will be prompted for the SSH password. After success, you can access remote files in /mnt/remote.

Unmounting the Directory

Use the following command to unmount:

fusermount -u /mnt/remote

If you get a permission error, try using sudo.

Configuring Automatic Mount at Boot

To enable automatic mounting at boot, complete two steps: configure SSH key-based authentication (passwordless login) and add a mount entry to /etc/fstab.

1. Set Up SSH Key Authentication

Generate an SSH key pair on the local machine:

ssh-keygen -t rsa

Press Enter to accept defaults (you can set a passphrase for added security). After generation, upload the public key to the remote host.

Recommended method: Use the ssh-copy-id command:

ssh-copy-id -i ~/.ssh/id_rsa.pub [email protected]

Afterwards, test SSH login to verify it no longer requires a password.

2. Add Auto-mount Entry to /etc/fstab

Edit the /etc/fstab file and add the following line at the end:

sshfs#[email protected]:/home /mnt/remote fuse defaults,_netdev,allow_other,reconnect,ServerAliveInterval=15,ServerAliveCountMax=3 0 0

Parameter explanation:

• _netdev: Declares this as a network device, ensuring the network is ready before mounting.
• reconnect: Enables automatic reconnection.
• ServerAliveInterval and ServerAliveCountMax: Keep the SSH connection alive to prevent timeouts.

After adding, test the configuration with sudo mount -a. The mount will be automatic after a reboot.

Alternative: Using a systemd Mount Unit

For systems using systemd, you can create a mount unit for more flexible management. For example, create /etc/systemd/system/mnt-remote.mount:

[Unit]
Description=SSHFS Mount for Remote Home
After=network-online.target
Wants=network-online.target

[Mount]
[email protected]:/home
Where=/mnt/remote
Type=fuse.sshfs
Options=_netdev,allow_other,reconnect,ServerAliveInterval=15,ServerAliveCountMax=3,IdentityFile=/home/localuser/.ssh/id_rsa

[Install]
WantedBy=multi-user.target

Then enable and start the unit:

sudo systemctl daemon-reload
sudo systemctl enable --now mnt-remote.mount

Useful Tips and Troubleshooting

Using SSH Config Aliases

Set an alias for the remote host in ~/.ssh/config:

Host remotehost
    HostName 111.111.111.111
    User user
    IdentityFile ~/.ssh/id_rsa

You can then simplify the mount command:

sshfs remotehost:/home /mnt/remote

The alias can also be used in /etc/fstab: sshfs#remotehost:/home ....

Common Issues

• Mount Point Permissions: Ensure the mount point directory exists and the user has access. To allow all users, add -o allow_other, but first ensure user_allow_other is uncommented in /etc/fuse.conf.
• Boot Mount Failure: Check if the network is ready (the _netdev parameter), if SSH key authentication is correctly configured, and if the remote host's SSH service allows public key authentication.
• Connection Timeout: Add ServerAliveInterval and ServerAliveCountMax to the mount options to maintain the connection.

Conclusion

SSHFS provides a secure and efficient solution for cross-server file management. By configuring SSH key authentication and using /etc/fstab or a systemd unit, you can achieve reliable automatic mounting at boot. It is well-suited for scenarios like storage expansion, backup synchronization, and remote development. Thorough testing in production environments is recommended, considering the impact of network stability.