Remove passphrase from private key

If you want to avoid creating new key just to remove annoying passphrase prompt after every operation, just do

$ openssl rsa -in ~/.ssh/id_rsa -out ~/.ssh/id_rsa.new

openssl will ask you passphrase, parse decoded idrsa and write out result to idrsa.new

Next, just replace idrsa with idrsa.new

$ mov ~/.ssh/id_rsa ~/.ssh/id_rsa.old
$ mov ~/.ssh/id_rsa.new ~/.ssh/id_rsa