I am planning to do a fresh install of ubuntu 11.10 in my system. Before that i have setuped key based ssh authentication in this machine. Is it possible to take backup of those ssh keys, so that i can use that in my new installation. Or else i must setup keybased ssh authentication again? If i can take backup, what are the files i need to copy? Can someone explain it in detail pls. Thanks in advance.
Responding to SSH only... yes, you can keep your keys.
I can't think of any topic on which to expound about that, though. It is straight forward: if your username is
karthick, then the keys are located in a hidden directory here:
id_rsa.pub file contains the public key used to authenticate. But there are other files to keep - all of them, really, such as
known_hosts for example. The MOST IMPORTANT is
id_rsa (note the lack of
.pub) as this is your private key. Back up each user. For example, if you set up SSH for
/root/.ssh as well. And so on for as many accounts as you have for this reason.
Each user has a directoy ~/.ssh, which typically contains the following files:
1) id_dsa private key of this user (different filename for rsa keys) 1) id_dsa.pub public key of this user 2) authorized_keys public key of other users (or same user on other machines) config personal configuration known_hosts host keys of other machines
Additionally, in /etc/ssh/, you will find:
3) ssh_host_dsa_key 3) ssh_host_dsa_key.pub 3) ssh_host_rsa_key 3) ssh_host_rsa_key.pub
Those are the host keys, keys identifying this computer.
You certainly want to backup all private and public keys. We call the machine in question home and the user user@home. Same person has an account user@remote and uses key-based login in both directions. What would happen if you loose any of the key files:
- You loose the identity of user@home.
ssh user@remotefrom home will no longer work with key based auth.
- user@remote loose the right to login to home with his key.
ssh user@homewill no longer work from remote with key based auth.
- You loose the identity of the host. user@remote will see a warning that host keys have changed when trying
ssh user@home. Depending on the configuration this will prevent him from logging in.