Master SSH Config: 8 Powerful Tips to Simplify Remote Access

Overview

SSH (Secure Shell) is a protocol that provides encrypted remote login and other network services, protecting against eavesdropping, DNS spoofing, and IP spoofing.

Simplifying SSH commands with ~/.ssh/config

By defining host aliases, usernames, key files and other options you can replace long commands such as ssh [email protected] with a short alias:

Host example
    HostName example.com
    User root
    # IdentityFile ~/.ssh/id_ecdsa
    # Port 22

After adding the block above, ssh example logs you in, and scp a.txt example:/home/user_name copies files without typing the full address.

Configuration files

SSH reads two configuration files, the user‑specific file takes precedence over the system‑wide file:

$HOME/.ssh/config    # user‑specific
/etc/ssh/ssh_config # system‑wide

Common configuration directives

Host – pattern that matches the host name (e.g. *, *.example.com, !*.dialup.example.com,*.example.com, 192.168.0.?).

AddKeysToAgent – automatically add keys to ssh-agent (values: no, confirm, ask, yes).

AddressFamily – address family to use ( any, inet, inet6).

BindAddress – local address to bind when the machine has multiple interfaces.

ChallengeResponseAuthentication – enable challenge‑response authentication ( yes / no).

Compression / CompressionLevel – enable compression and set level (1‑9, default 6).

ConnectionAttempts – number of retries before giving up (default 1).

ConnectTimeout – timeout in seconds for establishing the connection.

ControlMaster , ControlPath , ControlPersist – enable multiplexed connections, define the socket path and its lifetime.

GatewayPorts – allow remote hosts to connect to locally forwarded ports.

HostName – real host name or IP address.

IdentitiesOnly – restrict authentication to identities listed in the config.

IdentityFile – path to a private key; supports %d, %u, %l, %h, %r substitutions.

LocalCommand – command executed locally after a successful connection (requires PermitLocalCommand).

LocalForward / RemoteForward – set up port forwarding.

LocalForward [bind_address:]port host:hostport

RemoteForward [bind_address:]port host:hostport

PasswordAuthentication – enable/disable password login.

PermitLocalCommand – allow LocalCommand ( yes / no).

Port – remote SSH port (default 22).

ProxyCommand – command used to reach the server via a proxy (e.g. nc -X connect -x proxy:8080 %h %p).

User – login username.

Tip 1 – Manage multiple key pairs

Define separate host blocks for services that use different keys, avoiding the need to specify -i each time.

Host github
    HostName %h.com
    IdentityFile ~/.ssh/id_ecdsa_github
    User git
Host coding
    HostName git.coding.net
    IdentityFile ~/.ssh/id_rsa_coding
    User git

Cloning a repository then becomes as simple as git clone coding:deepzz/test.git.

Tip 2 – Edit remote files with Vim

$ vim scp://[email protected]//home/centos/docker-compose.yml
$ vim scp://example//home/centos/docker-compose.yml

Tip 3 – Use a remote service locally (LocalForward)

Forward a remote database port to a local port.

Host db
    HostName db.example.com
    LocalForward 5433 localhost:5432

After ssh db, connect locally with psql -h localhost -p 5433 orders.

Tip 4 – Forward remote traffic to local (RemoteForward)

Expose a local development server to a remote host.

Host remote
    HostName remote.example.com
    RemoteForward 8080 localhost:3000

Tip 5 – Share multiple connections (ControlMaster)

Enable multiplexing so several shells reuse a single TCP connection.

ControlMaster auto
ControlPath /tmp/%r@%h:%p

Tip 6 – Keyword login

Create a short alias for a server.

Host deepzz
    HostName deepzz.com
    User root
    # IdentityFile ~/.ssh/id_ecdsa
    # Port 22

Now ssh deepzz logs in directly.

Tip 7 – Proxy (jump) host

Use an intermediate gateway to reach internal servers.

Host gateway
    HostName proxy.example.com
    User root
Host db
    HostName db.internal.example.com
    User root
    ProxyCommand ssh gateway netcat -q 600 %h %p

Connect with ssh db.

Tip 8 – Remote command execution

Run commands or scripts on a remote host without opening an interactive shell.

# Single command
$ ssh example "cd /; ls"

# Multi‑line command
$ ssh example "
cd /
ls
"

# Execute a local script remotely
$ echo "cd /; ls" > test.sh
$ chmod +x test.sh
$ ssh example < test.sh

# Interactive command (e.g., top)
$ ssh -t example "top"

Reference

ssh_config manual: https://www.freebsd.org/cgi/man.cgi?query=ssh_config