Following this post, I\'m trying to transfer code from my local machine to the compute engine but I forgot my passphrase.
Can someone tell me how to retrieve it.
I\
this below works as stated by @cherba
rm ~/.ssh/google_compute_engine*
after using this command you can then reset the password to the ssh passphrase or you can simply hit enter to leave no password. i am supplying this answer because if you use the command and then attempt to ssh into an instance it takes a few seconds for the keys to propagate. i wanted to add this as a comment but didn't have enough reputation points on stack overflow.
Remove your old keys and try again, that is
rm ~/.ssh/google_compute_engine*
and then
gcloud compute ssh my_vm_name --zone zone_vm_is_in