MPI SSH without password?

[josephchrzempiec]

Hello This question is way above my head. I'm helping a friend of mine Who needed 9 Virtual Machine each one is using ubuntu server and openssh. Well 1 master host and 8 slave node. Systems so the master node is ubuntu 18.04 desktop the 8 other virtual michanes are ubuntu server 18.04. I know nothing about programing I'm more of hardware. I just only recently figure out how to setup a Virtual system.

So my question is as painless as i can get how can i setup a way for openssh server to be passwordless? here is his question from email.


Hi Jay,

The message passing software, MPI, needs to be able to ssh into the
slave nodes without a password. Currently the system is not configured
to do that. As a result, when I try to run my application, I get the
following messages:

johnb@johnbhost:~/terra$ mpiexec -n 8 -hostfile hostlist ./terra &
[3] 16334
johnb@johnbhost:~/terra$ Permission denied, please try again.
Permission denied, please try again.


Can someone please help me?



joseph

[howefield]

Thread moved to the "Server Platforms" forum.

[josephchrzempiec]

Hello thank you. Sorry still new to the fourms i wasn't sure where to post this at.

[TheFu]

For each client machine and userid, you must make an ssh-key. The command to do that is:

ssh-keygen -t ed25519

For each client-side userid -to- remote server, you need to push the public ssh-key (never the private), to the remote server. The command to do that is:

ssh-copy-id -i ~/.ssh/id_ed25519.pub username@remote

The "username" is optional and not needed if the same between the client machine and remote server.
"remote" can be a DNS name, IP address, some manually setup lookup inside the /etc/hosts or configured in the ~/.ssh/config file.

This only needs to be done once between the username@client and username-whatever@server. Don't screw with the ~/.ssh/ directory permissions or any file permissions inside. ssh-copy-id does the right thing. Test using ssh username@remote. No password should be requested.

These keys will work for ssh logins, scp, sftp, rsync, sshfs, x2go, and most backup tools. There must be 50 other tools that support ssh connections.

To make your life easier, the client-side ~/.ssh/config file is really handy for using a different port, different userid, making ugly dns-names into something short and memorable. The ssh_config manpage has all the settings possible. These are client-side only.