Multiple hosts SSH NO PASSWORD - each time it overrides the last key gen

UNIX macOS
1

Hello, here is my problem:

I have 20 machines that need to SSH into 1 machine throughout the day. The issue is every time I go through the process of putting my keys from one of the computers that needs to SSH to the server that needs to accept all the incoming SSH's it overrides the last one.

How do I tell the 1 computer that needs to be SSHed into from the other 20; all the keys of the 20, or maybe 1 file that contains all 20 key files from the computers that need to all connect to the 1 without entering password.

Thanks in advance.

2

Say the machine A is the machine to which the other 20 will ssh.

In Machine A you need to populate the authorized_keys file . Add the id_rsa.pub containt of each 20 machines in Machine A 's authorized file.

Now you can login from 20 machines without password

3

Again, as I told you in your other thread, search the forums first. And reading the documentation yourself wouldn't hurt either, even if it forces you to think for yourself instead of getting everything done by others.

If you just copy over the public key, or pipe into it using a single angle bracket, of course you'll overwrite it again and again. On each of the machines that should connect to the one in the center, run this

cat .ssh/id_rsa.pub | ssh user@target 'cat >> .ssh/authorized_keys'

Or install the new OpenSSH release, and create the appropriate certificates.

4

Excellent. That works and I appreciate it.

Now the next issue is that it takes FOREVER to SSH into the box. Over a minute, but it eventually goes through.... What do you think about that? Thnx

5

Do you have an proper DNS infrastructure in place? If not, that's your problem. With each connection, the SSH daemon will try and do an reverse lookup of your IP, and check if it matches the sent hostname. A reverse lookup without an appropriate record consumes time. Change/Add the directive

UseDNS no

, and the issue should disappear.

6

Can you elaborate on this? Where do I enter this info?

7

Sorry. That line belongs in your sshd_config, which should be somewhere below /etc. Usually, that line is already in there as

#UseDNS yes

which is the default.