SSH and command line

What's SSH?

SSH stands for Secure Shell, and refers to a protocol that allows to remotely control and administrate a machine using the command line interface (CLI). It is available by default in any terminal on GNU/Linux and macOS. On Windows, you may want to use MobaXterm (after launching it, click on Session then SSH).

The command line interface (CLI) is, in the computer world, the original (and more technical) way of interacting with a computer compared to graphical interface. Command line interfaces are generally said to be more complete, powerful or efficient than a graphical interface, though also more difficult to learn.

What address to use to connect to your server?

If you are installing at home (e.g. on a Raspberry Pi or OLinuXino or old computer):

  • you should be able to connect to your server using yunohost.local.
  • if yunohost.local does not work, your need to find out the local IP of the server.
  • if you installed a server at home but are attempting to connect from outside your local network, make sure port 22 is correctly forwarded to your server.

If your server is a remote server (VPS), your provider should have communicated you the IP address of the machine

In any cases, if you already configured a domain name pointing to the appropriate IP, it's much better to use yourdomain.tld instead of the IP address.

Login credentials

BEFORE running the post-installation

  • If you are installing at home, the default credentials are login: root and password: yunohost
  • If you are installing a remote server (VPS), your provider should have communicated you the login and password (or allowed you to configure an SSH key)

AFTER running the post-installation

During the postinstall, you've been asked to choose an administration password. This password becomes the new password for the root and admin users. Additionally, the root SSH login becomes disabled after the postinstall and you should log in using the admin user !. The only exception is that you may still be able to login using root from the local network - or from a direct console on the server (this is to cover the event where the LDAP server is broken and the admin user is unusable).

Connecting

The SSH command typically looks like:

# before the postinstall:
ssh root@11.22.33.44

# or after the postinstall:
ssh admin@11.22.33.44

Or using the domain name instead of the IP (more convenient):

ssh admin@your.domain.tld
# or with the special .local domain:
ssh admin@yunohost.local

If you changed the SSH port, you need to add -p <portnumber> to the command, e.g.:

ssh -p 2244 admin@your.domain.tld

If you connected as admin and would like to become root for convenience (e.g. to avoid typing sudo in front of every command), you can become root using the command sudo su or sudo -i.

Which other users may connect to the server?

By default, only the admin user can log in to YunoHost SSH server.

YunoHost's users created via the administration interface are managed by the LDAP directory. By default, they can't connect via SSH for security reasons. If you want some users to have SSH access enabled, use the command:

yunohost user ssh allow <username>

It is also possible to remove SSH access using the following:

yunohost user ssh disallow <username>

Finally, it is possible to add, delete and list SSH keys, to improve SSH access security, using the commands:

yunohost user ssh add-key <username> <key>
yunohost user ssh remove-key <username> <key>
yunohost user ssh list-keys <username>

Security and SSH

N.B. : fail2ban will ban your IP for 10 minutes if you perform 5 failed login attempts. If you need to unban the IP, have a look at the page about Fail2Ban

A more extensive discussion about security & SSH can be found on the dedicated page.

Yunohost command line

Providing a full tutorial about the command line is quite beyond the scope of the YunoHost documentation : for this, consider reading a dedicated tutorial such as this one or this one. But be reassured that you don't need to be a CLI expert to start using it !

The yunohost command can be used to administrate your server and perform the various actions similarly to what you do on the webadmin. The command must be launched either from the root user or from the admin user by preceeding them with sudo. (ProTip™ : you can become root with the command sudo su as admin).

YunoHost commands usually have this kind of structure :

yunohost app install wordpress --label Webmail
          ^    ^        ^             ^
          |    |        |             |
    category  action  argument      options

Don't hesitate to browse and ask for more information about a given category or action using the the --help option. For instance, those commands :

yunohost --help
yunohost user --help
yunohost user create --help

will successively list all the categories available, then the actions available in the user category, then the usage of the action user create. You might notice that the YunoHost command tree is built with a structure similar to the YunoHost admin pages.

Found errors? Think you can improve this documentation? Simply click the Edit link at the top of the page, and then the icon on Github to suggest changes.