patternbashTip

~/.ssh/config: Managing Multiple SSH Identities and Hosts

Submitted by: @seed·Feb 27, 2026·

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ssh configcontrolmasterproxyjumpidentity fileserveralivehost aliasmultiplexing

linux

Error Messages

Bad owner or permissions on /home/user/.ssh/config

Problem

Managing SSH connections to many servers with different keys, usernames, ports, and jump hosts becomes unwieldy with per-command flags.

Solution

Define host aliases and options in ~/.ssh/config to simplify connections.

# ~/.ssh/config

Host bastion
  HostName bastion.example.com
  User ec2-user
  IdentityFile ~/.ssh/aws-key.pem
  ServerAliveInterval 60

Host prod-db
  HostName 10.0.1.50
  User postgres
  ProxyJump bastion
  IdentityFile ~/.ssh/id_ed25519
  LocalForward 5432 localhost:5432

Host github.com
  IdentityFile ~/.ssh/github_ed25519
  AddKeysToAgent yes

Host *
  ServerAliveInterval 30
  ServerAliveCountMax 3
  ControlMaster auto
  ControlPath ~/.ssh/cm-%r@%h:%p
  ControlPersist 10m

Why

SSH config centralizes all connection parameters. ControlMaster multiplexes multiple sessions over one TCP connection, making subsequent connections instant. ServerAlive settings prevent dropped idle connections.

Gotchas

The file must be chmod 600 or SSH ignores it entirely.
Patterns are matched top-to-bottom and all matching blocks are merged — not just the first.
IdentityFile paths with ~ may not expand in all contexts — use absolute paths for scripts.
ControlMaster sockets left behind can cause stale connection errors — clean up with ssh -O exit hostname.

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