How often do you copy and paste the contents of ~/.ssh/id_rsa.pub to remote ~/.ssh/authorized_keys?
With ssh-copy-id its easy!
Say you need to copy your public key to example.com, this would do the trick:
Here is the man file:
ssh-copy-id – install your public key in a remote machine’s authorized_keys
ssh-copy-id [-i [identity_file]] [user@]machine
ssh-copy-id is a script that uses ssh to log into a remote machine and append the indicated identity file to that machine’s ~/.ssh/authorized_keys file.
If the -i option is given then the identity file (defaults to ~/.ssh/id_rsa.pub) is used, regardless of whether there are any keys in your ssh-agent. Otherwise, if this:
provides any output, it uses that in preference to the identity file.
If the -i option is used, or the ssh-add produced no output, then it uses the contents of the identity file. Once it has one or more fingerprints (by whatever means) it uses ssh to append them to ~/.ssh/authorized_keys on the remote machine (creating the
file, and directory, if necessary.)
This program does not modify the permissions of any pre-existing files or directories. Therefore, if the remote sshd has StrictModes set in its configuration, then the user’s home, ~/.ssh folder, and ~/.ssh/authorized_keys file may need to have group writabil‐
ity disabled manually, e.g. via
chmod go-w ~ ~/.ssh ~/.ssh/authorized_keys
on the remote machine.
ssh(1), ssh-agent(1), sshd(8)