Hi Michael,
Thanks very much, this is really cool! I need to look into the
HostbasedAuthentication for intra-cluster MPI tasks spawned by SSH (not
using srun).
Presumably external access still needs to use SSH authorized keys?
Best regards,
Ole
On 09-06-2020 17:45, Michael Jennings wrote:
On Tuesday, 09 June 2020, at 12:43:34 (+0200),
Ole Holm Nielsen wrote:
in which case you need to set up SSH authorized_keys files for such
users.
I'll admit that I didn't know about this until I came to LANL, but
there's actually a much better alternative than having to create user
key pairs and manage users' ~/.ssh/authorized_keys files: Host-based
Authentication.
Setting "HostbasedAuthentication yes" and configuring it properly on
all the cluster hosts allows a cryptographically-secured equivalent of
what used to be known as RHosts-style Authentication using ~/.rhosts
and /etc/hosts.equiv. Essentially, it allows host-key-authenticated
systems to recognize each other, and once that completes successfully,
the target host trusts the source host to accurately introduce the
user who's logging in.
Once you have host-based authentication working, users can SSH around
inside your cluster seamlessly (subject to additional restrictions, of
course, like access.conf or pam_slurm_adopt) without needing hackish
extra utilities to create and manage cluster-specific passphraseless
key pairs for every single user! :-)
There's a great cookbook online that tells you step-by-step how to set
it up: https://en.wikibooks.org/wiki/OpenSSH/Cookbook/Host-based_Authentication
