ssh用の鍵を作成

$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/hoge/.ssh/id_rsa):
  [enter]を入力
Enter passphrase (empty for no passphrase):
  パスフレーズを入力
Enter same passphrase again:
  確認のためパスフレーズを再入力
Your identification has been saved in /home/hoge/.ssh/id_rsa.
Your public key has been saved in /home/hoge/.ssh/id_rsa.pub.

秘密鍵のパスフレーズを「なし」に変更する方法です。

$ cp id_rsa id_rsa.nopass
$ ssh-keygen -p
Enter file in which the key is (/home/hoge/.ssh/id_rsa): /home/hoge/.ssh/id_rsa.nopass
Enter old passphrase:
先ほど設定したパスフレーズ
Key has comment '/home/hoge/.ssh/id_rsa.nopass'
Enter new passphrase (empty for no passphrase):
  Enterを入力
Enter same passphrase again:
  Enterを入力
Your identification has been saved with the new passphrase.