ssh-add Command Examples in Linux

The ssh-add command adds private key identities to the SSH key agent. If the key is protected by a password, the user only needs to enter the password once, and the agent will automatically authenticate the user.

ssh-add has a few decent options available, some of which are handy to know about.

-l will allow you to see loaded identities, along with their fingerprints:

$ ssh-add -l
256 SHA256:P7FdkmbQQFoy37avbKBfzMpEhVUaBY0TljwYJyNxzUI vagrant@centos1 (ED25519)

-D will allow you to remove all identities (and -d can be used to remove specific ones):

$ ssh-add -D
All identities removed.

-x will lock an agent, while -X will unlock it:

$ ssh-add -l
256 SHA256:P7FdkmbQQFoy37avbKBfzMpEhVUaBY0TljwYJyNxzUI vagrant@centos1 (ED25519)

$ ssh-add -x
Enter lock password: 
Again: 
Agent locked.

$ ssh-add -l
The agent has no identities.

$ ssh-add -X
Enter lock password: 
Agent unlocked.

$ ssh-add -l
256 SHA256:P7FdkmbQQFoy37avbKBfzMpEhVUaBY0TljwYJyNxzUI vagrant@centos1 (ED25519)

ssh-add Command Examples

1. Add the default ssh keys in `~/.ssh` to the ssh-agent:

# ssh-add

2. Add a specific key to the ssh-agent:

# ssh-add path/to/private_key

3. List fingerprints of currently loaded keys:

# ssh-add -l

4. Delete a key from the ssh-agent:

# ssh-add -d path/to/private_key

5. Delete all currently loaded keys from the ssh-agent:

# ssh-add -D

6. Add a key to the ssh-agent and the keychain:

# ssh-add -K path/to/private_key