I can ssh into this machine ssh user@remote_machine.com and it always works. However I discovered that ssh-add -l shows no key (I had to replace my laptop a month ago). Does it mean that the ssh tool doesn't use the ssh agent?

What is the agent used for then?

1 Answer 1


ssh by default will check for certain identity files, for example ~/.ssh/id_rsa. However, you can specify alternative identity files with -i. See man ssh for details.

ssh-agent helps manage identity files:

From man ssh-agent:

Multiple identities may be stored in ssh-agent concurrently and ssh(1)
will automatically use them if present.

One benefit of using ssh-agent is that if your private key is password-protected (recommended), you can unlock it once when adding it to your ssh-agent and you won't need to re-enter the password every time you use it.

Other benefits include agent forwarding. See man ssh for details.

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