Keeping an SSH SOCKS5 Proxy Alive

Abstract

Explains how to create a systemd service for a persistent ssh socks5 proxy.

Overview

This post shows how to create a systemd service for a persistent ssh socks5 proxy.

Prerequisites

• Key-based authentication enabled for a remote ssh server.
• Host specification for the server is defined in ~/.ssh/config, with cloudvm as the host name.

See this post.

Systemd Unit File

Create a user level unit file ~/.config/systemd/user/ssh-socks5.service, and put the following content in it:

[Unit]
Description=Persistent SSH SOCKS5 Proxy
After=network-online.target

[Service]
Type=simple
ExecStart=/usr/bin/ssh -N -D 1080 cloudvm \
    -o ServerAliveInterval=10 \
    -o ServerAliveCountMax=3 \
    -o ExitOnForwardFailure=yes \
    -o TCPKeepAlive=yes
Restart=always
RestartSec=5

[Install]
WantedBy=default.target

Note the reason to setup a user level service instead of a system level service is that the host specification for cloudvm (i.e., ~/.ssh/config) is defined in the user’s home directory, so system level service would not see it unless using absolute path (which is inconvenient).

After creating the unit file, run the following commands to start and examine the status of the service:

systemctl --user daemon-reload
systemctl --user enable ssh-socks5.service
systemctl --user start ssh-socks5.service
systemctl --user status ssh-socks5.service

After the setup, the socks5 proxy should be available through socks5://127.0.0.1:1080.