Use the ssh-keygen command with the -p flag to change or remove the passphrase for an SSH RSA private key file.
Change or remove the passphrase
Run ssh-keygen with -p only will prompt you for the location of the keyfile (defaulting to ~/.ssh/id_rsa) the old passphrase and the new passphrase:
You will be prompted for the location of the file, which you can specify or hit <enter> to leave as the default:
Enter file in which the key is (/home/chris/.ssh/id_rsa):
Now enter the old passphrase, the new one and confirm it:
Enter old passphrase: Enter new passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved with the new passphrase.
To remove the existing passphrase, simply hit <enter> at the steps where you enter the new one and then confirm it.
Other command line flags
You can also specify the path to the file when first calling ssh-keygen:
ssh-keygen -p -f /path/to/file
And even supply the old pass phrase and new ones of the command line, although I wouldn’t recommend it unless you clear the bash session history afterwards:
ssh-keygen -p -f /path/to/file -P old_passphrase -N new_passphrase
To remove the passphrase without having to hit <enter> twice in the prompts, but have to type in the existing one so it’s not visible on the command line:
ssh-keygen -p -N ""
You can of course optionally add the -f flag to this one too.