Trouble running shell script

I have a schell script called “backup.sh”
it sits in /config
I can happily run it from the HA terminal
/bin/bash /config/backup.sh
But when i add it to my configuration.yaml and try and run it as a service I get
[homeassistant.components.shell_command] Error running command: /bin/bash /config/backup.sh, return code: 127
127 iirc is file not found?
This is my config:

shell_command:
  run_backup: /bin/bash /config/backup.sh

the file has the relevant permissions and I have already tried chmod +x /config/backup.sh

Take a look at this discussion:

I did see that, and its clear as mud :joy:
I have tried generating some keys as discussed then updating my config to:

> shell_command:
>   run_backup: ssh -i /config/.ssh/jimmy_rsa -o 'StrictHostKeyChecking=no'  [email protected] 'bash /config/backup.sh'

which gives me error 255