[ubuntu-11.10] How to add RSA key to authorized_keys file?

I've created an RSA public key and I want to add that to authorized_keys file, but there is no such file in my Ubuntu 11.10 machine.

How can I add the key to authorized_keys?

There is already a command in the ssh suite to do this automatically for you. I.e log into a remote host and add the public key to that computers authorized_keys file.

ssh-copy-id -i /path/to/key/file [email protected]

If the key you are installing is ~/.ssh/id_rsa then you can even drop the -i flag completely.

Much better than manually doing it!

Make sure when executing Michael Krelin's solution you do the following

cat <your_public_key_file> >> ~/.ssh/authorized_keys

Note the double > without the double > the existing contents of authorized_keys will be over-written (nuked!) and that may not be desirable

mkdir -p ~/.ssh/

To overwrite authorized_keys

cat your_key > ~/.ssh/authorized_keys

To append to the end of authorized_keys

cat your_key >> ~/.ssh/authorized_keys

>ssh user@serverip -p portnumber 
>sudo bash (if user does not have bash shell else skip this line)
>cd /home/user/.ssh
>echo ssh_rsa...this is the key >> authorized_keys

I know I am replying too late but for anyone else who needs this, run following command from your local machine

cat ~/.ssh/id_rsa.pub | ssh [email protected] "mkdir -p ~/.ssh && cat >> ~/.ssh/authorized_keys && chmod 600 ~/.ssh/authorized_keys"

this has worked perfectly fine. All you need to do is just to replace

[email protected]

with your own user for that particular host