use ssh config defaults without hostname

Question

Is it somehow possible to use a default ssh config without a hostname? of course I know how to use ~/.ssh/config, but I want to do something like:

Host myservers
  User root
  IdentitiesOnly yes
  IdentityFile ~/.ssh/specialkey

• ssh myservers server1.de
• ssh myservers server2.de

but that wont work, so I cannot use a ssh config and define the server/hostname afterwards. That means for now I always have to do ssh -i ~/.ssh/specialkey -O IdentitiesOnly=yes [email protected] or what other possibilities would I have here to use?

Answer 1

Modify the snippet so it applies to the hosts in question:

Host server1.de server2.de
  User root
  IdentitiesOnly yes
  IdentityFile ~/.ssh/specialkey

Then you just ssh server1.de or ssh server2.de.

You can add more entries to the Host line. If the settings should apply to a group of servers with a common naming scheme, consider using wildcards. E.g. Host server*.de.

Make sure you put the snippet early enough in your config (because the first obtained value for each parameter is used). Definitely before Host *.

---

If you want to use some special config on demand, put the config in another file and use ssh -F.

-F configfile
Specifies an alternative per-user configuration file. If a configuration file is given on the command line, the system-wide configuration file (/etc/ssh/ssh_config) will be ignored. The default for the per-user configuration file is ~/.ssh/config. […]

^(source)

Example:

ssh -F ~/.ssh/myservers server1.de

Notes:

• The config may contain Host * as the only section, so it will work for any server you want.

• You can create two or more configs, each in a separate file, and pick whichever you want when you connect.

• An alias

  alias ssh-myservers='ssh -F ~/.ssh/myservers'
  

  will allow you to connect almost as you wanted: ssh-myservers server1.de.

• A wrapper script or a shell function can allow you to connect exactly as you wanted. Example function:

  ssh() {
     configfile=~/".ssh/$1"
     if [ -f "$configfile" ]; then
        shift; command ssh -F "$configfile" "$@"
     else
        command ssh "$@"
     fi }
  

  To connect with ssh myservers server1.de you need the config to be in ~/.ssh/myservers.