SSH Config File Settings

Description

The SSH config file allows each user to define specific SSH options for connecting to multiple different remote hosts.

Instructions

Files

~/.ssh/config

This is the per-user configuration file. This file is used by the SSH client. Because of the potential for abuse, this file must have strict permissions: read/write for the user, and not writable by others.

/etc/ssh/ssh_config

Systemwide configuration file. This file provides defaults for those values that are not specified in the user’s configuration file, and for those users who do not have a configuration file. This file must be world-readable.

If these files don’t exist, you may need to create them first.

If the config file is new, you might need to set the following permissions:

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$ chmod 600 ~/.ssh/config

This ensures that ONLY your user has access to edit this file.

Example 1: Basic Usage

The following example can be used to setup pre-defined connections to hosts on your local network.

~/.ssh/config

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Host my-ssh-host
  HostName 10.0.0.5
  Port 22
  ForwardX11 no
  User anthony
  Compression no
  IdentityFile ~/.ssh/id_rsa
  IdentitiesOnly yes

Sample connection:

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$ ssh my-ssh-host

Example 2: Connecting to GitHub.com

The following example allows you to connect to multiple github.com accounts using seperate keys for each connection. Since GitHub.com does not allow the use of the same SSH key accross multiple accounts.

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Host podcast
    HostName github.com
    IdentityFile ~/.ssh/podcast
Host example.com
    HostName github.com
    IdentityFile ~/.ssh/example.com
Host radio
    HostName github.com
    IdentityFile ~/.ssh/radio

In the above example three host entries are defined; podcast, example.com, and radio.

The HostName for each Host entry points to github.com

A unique IdentityFile is specified for each Host entry.

Verify that the permissions of each IdentityFile are 400.

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$ chmod 400 ~/.ssh/id_rsa_github

This verifies that the file is read-only and accessible only by your user.

The following example shows how to reference each git repo based on the above config file:

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$ git clone git@{HOST}:{ORG_NAME}/{REPO_NAME}.git

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git@podcast:username/podcast.git
[email protected]:username/example.com.git
git@radio:username/radio.git

Sources

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