Your aim
You want to use Linux and OpenSSH to automize your tasks. Therefore you need an automatic login from host A
/ user a
to Host B
/ user b
. You don't want to enter any passwords, because you want to call ssh from a within a shell script.
How to do it
First log in on A
as user a
and generate a pair of authentication keys. Do not enter a passphrase:
a@A ~ $ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/a/.ssh/id_rsa):
Created directory '/home/a/.ssh'.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/a/.ssh/id_rsa.
Your public key has been saved in /home/a/.ssh/id_rsa.pub.
The key fingerprint is:
3e:4f:05:79:3a:9f:96:7c:3b:ad:e9:58:37:bc:37:e4 a@A
The key's randomart image is:
+--[ RSA 2048]----+
| |
| |
| . |
| . o|
| S o .Eo|
| o * = o.|
| = B + o|
| = + oo..|
| o o. o=|
+-----------------+
Now use ssh to create a directory ~/.ssh
as user b
on B
. (The directory may already exist, which is fine):
a@A ~ $ ssh b@B mkdir -p ~/.ssh
b@B's password:
Finally append a
's new public key to b@B:~/.ssh/authorized_keys
and enter b's password one last time:
a@A ~ $ cat ~/.ssh/id_rsa.pub | ssh b@B 'cat >> ~/.ssh/authorized_keys'
b@B's password:
From now on you can log into B
as b
from A
as a
without password:
a@A ~ $ ssh b@B hostname
B
Depending on your version of SSH you might also have to do the following changes:
-
put the public key in
~/.ssh/authorized_keys2
; -
change the permissions of
~/.ssh
to 700; -
change the permissions of
~/.ssh/authorized_keys2
to 640.
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