How do I backup ssh keys?

Question

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.

Solution 1

Cryptographic keys which you may want to backup.

• ~/.gnupg/*
• ~/.pki/nssdb/*
• ~/.gnome2/keyrings/*
• ~/.ssh/*
• /usr/local/apache2/conf/ssl.crt/server.crt
• /usr/local/apache2/conf/ssl.key/server.key
• /etc/ssh/*
• /etc/ssl/private/*
• /etc/cups/ssl/*

Solution 2

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:

1. You loose the identity of user@home. ssh user@remote from home will no longer work with key based auth.
2. user@remote loose the right to login to home with his key. ssh user@home will no longer work from remote with key based auth.
3. 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.

Comments

[Caesium]

You missed the very one he asked about (~/.ssh) but a good list nonetheless :)

[Tom]

You also missed /etc/ssh

[Admin]

To answers to questions not asked... :)

[illya]

Great list! It's harder to google for such a list than it should be. Thank you for providing it.