SSH

What's SSH?

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

During YunoHost installation

Find your IP

If you are installing on a VPS, then your VPS provider should have gave you your IP address.

If you are installing at home (e.g. on a Raspberry Pi or OLinuXino), then you need to find out which IP has been attributed to your board after you plugged it to your internet box / router. Several ways exists to find your server's IP :

open a terminal and use sudo arp-scan --local to list the IP on your local network ;
use your internet box / router interface to list the machines connected, or check the logs ;
plug a screen on your server, log in and type hostname --all-ip-address.

Connect

Assuming your IP address is 111.222.333.444, open a terminal and enter :

ssh root@111.222.333.444

A password will be asked. If this is a VPS, your VPS provided should have communicated you the password. If you used a pre-installed image (for x86 computer or ARM board), the password should be yunohost.

Since YunoHost 3.4, after running the postinstallation, you won't be able to login as `root` anymore. Instead, **you should login using the `admin` user !** In the event that the LDAP server is broken and the `admin` user is unusable, you may still however still be able to login using `root` from the local network.

Change the password!

After logging in for the first time, you should change the root password. The server might automatically ask you to do so. If not, use the command passwd. It is important to choose a reasonably strong password. Note that the root password will be overriden by the admin password when you perform the postinstallation.

After installing YunoHost

If you installed your server at home and are attempting to connect from outside your local network, make sure port 22 is correctly forwarded to your server. (Reminder : since YunoHost 3.4 you should connect using the admin user !)

If you only know the IP address of your server :

ssh admin@111.222.333.444

Then, you need to enter your administrator password created at post-installation step.

If you configured your DNS (or tweaked your /etc/hosts), you can simply use your domain name :

ssh admin@your.domain.tld

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 are connected as `admin` and would like to become `root` for more comfort (e.g. to avoid typing `sudo` in front of every command), you can become `root` using the command `sudo su`.

Which users?

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 mimutes 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.

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SSH