[vagrant@localhost ~]$ ssh -T git@gitlab.com
Permission denied (publickey).

[vagrant@localhost ~]$ ssh-keygen -C "ログイン時のアドレス@fuga.com" -t rsa

Host gitlab
    HostName gitlab
    User git
    IdentityFile ~/.ssh/id_rsa

[vagrant@localhost .ssh]$ ssh -T git@gitlab.com
Permission denied (publickey).

/home/vagrant/.ssh/id_rsa already exists.
Overwrite (y/n)? y