From Linux Man Pages
ssh-copy-id - install your identity.pub in a remote machine's authorized_keys
ssh-copy-id [-i [identity_file]] [user@]machine
DESCRIPTION
ssh-copy-id is a script that uses ssh to log into a remote machine (presumably using a login password, so pass-
word authentication should be enabled, unless you've done some clever use of multiple identities)
It also changes the permissions of the remote user's home, ~/.ssh, and ~/.ssh/authorized_keys to remove group
writability (which would otherwise prevent you from logging in, if the remote sshd has StrictModes set in its
configuration).
If the -i option is given then the identity file (defaults to ~/.ssh/identity.pub) is used, regardless of whether
there are any keys in your ssh-agent. Otherwise, if this:
ssh-add -L
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)
RELATED
ssh(1), ssh-agent(1), sshd(8)
CATEGORY