Purpose

Configure SSH connections, key management, jump hosts, and tmux sessions for reliable remote workflows.

When to use this skill

• setting up ~/.ssh/config with host aliases, ProxyJump, and multiplexing
• creating persistent tmux sessions for long-running remote work
• syncing files between local and remote with rsync
• debugging SSH connection failures or key issues

Do not use this skill when

• writing systemd unit files on the remote host — prefer systemd-services
• the task is container orchestration — different domain
• doing local terminal debugging — prefer terminal-debugging

Procedure

1. Generate keys — ssh-keygen -t ed25519 -C "user@machine". Copy: ssh-copy-id user@host.
2. Configure SSH — edit ~/.ssh/config with host blocks for aliases, jump hosts, multiplexing.
3. Enable multiplexing — ControlMaster auto, ControlPath ~/.ssh/sockets/%r@%h-%p, ControlPersist 600.
4. Jump hosts — use ProxyJump bastion to reach internal hosts through a bastion.
5. Persistent tmux — ssh host -t 'tmux new -s work || tmux attach -t work'.
6. Sync files — rsync -avz --exclude .git/ ./src/ host:~/project/src/.
7. Port forwarding — ssh -L 8080:localhost:3000 host for local access to remote services.
8. Debug — ssh -vvv host for verbose output; check /var/log/auth.log on server.

SSH config example

Host *
    AddKeysToAgent yes
    IdentityFile ~/.ssh/id_ed25519
    ControlMaster auto
    ControlPath ~/.ssh/sockets/%r@%h-%p
    ControlPersist 600
    ServerAliveInterval 60

Host bastion
    HostName bastion.example.com
    User deploy

Host internal
    HostName 10.0.1.50
    User deploy
    ProxyJump bastion

tmux essentials

tmux new -s dev           # new named session
tmux attach -t dev        # reattach
# Ctrl-b d  detach    Ctrl-b c  new window
# Ctrl-b %  vsplit    Ctrl-b "  hsplit

Decision rules

• Use ed25519 keys — faster and more secure than RSA.
• Use ProxyJump over ssh -J — config is version-controllable.
• Create ~/.ssh/sockets/ directory — missing dir causes silent multiplexing failure.
• Set ServerAliveInterval 60 to prevent dropped idle connections.
• Use tmux new -s name || tmux attach -t name to be idempotent.

References

• https://man.openbsd.org/ssh_config
• https://github.com/tmux/tmux/wiki

Related skills

• linux-ubuntu-ops — server management after SSH access
• bash — scripting remote commands
• terminal-debugging — debugging remote processes