Add multiple SSH keys to a new server

Question

I know I can do the following to copy an SSH key

ssh-copy-id user@server.com

but when I deploy a new server, I need to authorize multiple SSH keys to it. Is there anyway to make life easier for authorizing multiple SSH keys?

Answer 1

Reading the man-page of ssh-copy-id, it seems that it should copy all the keys from the ssh-agent that aren't accepted for login. So, load all the keypairs into ssh-agent using ssh-add and use ssh-copy-id after that.

If that doesn't work, you can try specifying the keys for ssh-copy-id:

for i in ~/.ssh/*.pub; do
  ssh-copy-id -i $i user@host
done

If that still doesn't work for you, maybe take a look at something like ansible:

# sshkeys.yml
---
- hosts: all
  remote_user: foo
  tasks:
  - authorized_key:
      user: foo
      key: '{{lookup("file", item)}}'
    with_items:
    - id_rsa.pub
    - id_rsa_alternate.pub

Use like:

ansible-playbook -i remote.host.com, -k sshkeys.yml

Be sure to read more about ansible if you choose to go this route.

Answer 2

INTRO

This way beats ssh copy id by miles as you can copy the keys to any user, for an ssh server with any port, not just 22. oh and u can have multiple keys in your authorized_keys.org that will get appended to the authorized_keys file on the server. Make sure authorized_keys.org has one ssh public key per line.

There are many ways you can construct these lines to your likeing. I suggest never forgetting this cat | ssh cat method or the similar echo | ssh ssh cat method, as they are perfect for writing on remote servers. cat SOMETHING | ssh SERVER "cat - > REMOTEFILE" or you can use echo like so echo "SOMETHING" | ssh SERVER "cat - > REMOTEFILE" these are perfect methods to read in something locally & then write it or append it on another server. Write it like this cat - > REMOTEFILE or append it like this cat - >> REMOTEFILE

THE ANSWERS

cat authorized_keys.org | ssh -p 22 root@server.com "cat - >> /root/.ssh/authorized_keys"

or

cat authorized_keys.org | ssh -p 22 root@server.com "cat - >> ~/.ssh/authorized_keys"

Also if you have the ssh key (one ssh key):

cat id_rsa.pub | ssh -p 22 root@server.com "cat - >> /root/.ssh/authorized_keys"

or

cat id_rsa.pub | ssh -p 22 anyuser@server.com "cat - >> ~/.ssh/authorized_keys"

That should be enough to make sense of it all.

MORE INFO

NOTE: Read my comments below on the fact that your not limited to using "root". Here you can see all parts of it are modifyable:

[input of ssh keys or keys (as long as new line sepearted)] | ssh -p PORT USER@SERVER "cat - >> AUTHORIZEDKEY"

BONUS: lets say that ssh server doesnt allow password logins and only allows SSH keys, yet you want to let it know about more key[s].

• [input of ssh keys or keys (as long as new line sepearted)] | ssh -i PRIVATE -p PORT USER@SERVER "cat - >> AUTHORIZEDKEY"
• [input of ssh keys or keys (as long as new line sepearted)]: this can be a cat of a file with 1 or more public keys as long as they are new line sepeareted or an echo of a full public key (or many public keys, again as long as they are new line seperated - you can use "echo -e 'line1\nline2'" to seperate new lines with echo.)
• PRIVATE: if your ssh server only lets a certain key in, because it has ssh key auth only configured and it has your public key. then specify the private key of that public key key
• USER: the user to which you want to connect and edit its key. If you connect as root (example: root@server.com), you can add to anyones keys "cat - >> /home/anyuser/.ssh/authorized_keys" or you can add to roots keys "cat - >> /root/.ssh/autorized_keys" . However if you connect up as user1 then you can only change user1s keys "cat - >> /home/user1/.ssh/authorized_keys" or more simply "cat - >> ~/.ssh/authorized_keys" (this last one works for any user).
• SERVER: the server you want to connect to. In this case its server.com
• PORT: the accepted SSH server port on the server. Usually its Port 22. Note if its port 22 you can leave out "-p 22" as that is default.
• AUTHORIZEDKEY: this is the location of the authorized_keys. I covered this in USER point. This will either be "/root/.ssh/authorized_keys" or "/home/user1/.ssh/authorized_keys" or "~/.ssh/authorized_keys"