You may encounter the following error when you try to access GitHub via SSH on Linux:

ssh -vT git@github.com
# ...
# Agent admitted failure to sign using the key.
# debug1: No more authentication methods to try.
# Permission denied (publickey).

For more details, see this issue report.

Resolution

You should be able to fix this error by simply loading your keys into your SSH agent with ssh-add:

ssh-add
# Enter passphrase for /home/you/.ssh/id_rsa: [tippy tap]
# Identity added: /home/you/.ssh/id_rsa (/home/you/.ssh/id_rsa)

If your key does not have the default filename (/.ssh/id_rsa), you'll have to pass that path to ssh-add:

ssh-add ~/.ssh/my_other_key
# Enter passphrase for /home/you/.ssh/my_other_key: [tappity tap tap]
# Identity added: /home/you/.ssh/my_other_key (/home/you/.ssh/my_other_key)