SSH/SFTP Connection to a Compute Session¶
Backend.AI supports SSH/SFTP connection to the created compute sessions (containers). In this section, we will learn how to do it.
SSH/SFTP connection is supported only on desktop apps, and not yet supported on web-based Web-UI service.
For Linux / Mac¶
First, create a compute session, then click the app icon (first button) in Control, followed by SSH / SFTP icon. Then, a daemon that allows SSH/SFTP access from inside the container will be initiated, and the Web-UI app interacts with the daemon through a local proxy service.
You cannot establish a SSH/SFTP connection to the session until you click the SSH/SFTP icon. When you close the Web-UI app and launch it again, the connection between the local proxy and the Web-UI app is initialized, so the SSH/SFTP icon must be clicked again.
Next, a dialog containing SSH/SFTP connection information will be pop up.
Remember the address (especially the assigned port) written in the SFTP URL and
click the download link to save the
id_container file on the local machine.
This file is an automatically generated SSH private key. Instead of using the
link, you can also download the
id_container file located under
/home/work/ with your web terminal or Jupyter Notebook. The auto-generated
SSH key may change when new session is created. In that case, it must be
To SSH connect to the compute session with the downloaded SSH private key, you
run the following command in the shell environment. You should write the
path to the downloaded
id_container file after
-i option and the
assigned port number after
-p option. The user inside the compute session is
usually set to
work, but if your session uses other account, the
work@localhost should be changed to the actual session account. If
you run the command correctly, you can see that SSH connection is made to the
compute session and you are welcomed by the container’s shell environment.
$ ssh -o StrictHostKeyChecking=no \ > -o UserKnownHostsFile=/dev/null \ > -i ~/.ssh/id_container \ > work@localhost -p 52468 Warning: Permanently added '[127.0.0.1]:52468' (RSA) to the list of known hosts. f310e8dbce83:~$
Connecting by SFTP would almost be the same. After running the SFTP client and
setting public key-based connection method, simply specify
as the SSH private key. Each FTP client may adopt different way, so refer to
each FTP client manual for details.
The SSH/SFTP connection port number is randomly assigned each time when a session is created. If you want to use a specific SSH/SFTP port number, you can input the port number in the “Preferred SSH Port” field in the user settings menu. To avoid possible collisions with other services within the compute session, it is recommended to specify a port number between 10000-65000. However, if SSH/SFTP connections are made by two or more compute sessions at the same time, the second SSH/SFTP connection cannot use the designated port (since the first SSH/SFTP connection has already taken it), so a random port number will be assigned.
If you want to use your own SSH keypair instead of
id_container, create a
user-type folder named
.ssh. If you create
authorized_keys file in
that folder and append it with the contents of your SSH public key, you can
connect by SSH/SFTP through your own SSH private key without having to
id_container after creating a compute session.
For Windows / FileZilla¶
Backend.AI Web-UI app supports OpenSSH-based public key connection (RSA2048).
To access with a client such as PuTTY on Windows, a private key must be
converted into a
ppk file through a program such as PuTTYgen. You can refer
to the following link for the conversion method:
https://wiki.filezilla-project.org/Howto. For easier explanation, this section
will describe how to connect to SFTP through FileZilla client on Windows.
Refer to the connection method on Linux/Mac, create a compute session, check the
connection port and download
id_container is an
OpenSSH-based key, so if you use a client that supports only Windows or ppk type
keys, you must convert it. Here, we will convert through the PuTTYgen program
installed with PuTTY. After running the PuTTYgen, click on the import key in the
Conversions menu. Select the downloaded
id_container file from the file open
dialog. Click the Save private key button of PuTTYGen and save the file with the
After launching the FileZilla client, go to the Settings-Connection-SFTP
and register the key file
id_container for clients
Open Site Manager, create a new site, and enter the connection information as follows.
When connecting to a container for the first time, the following confirmation popup may appear. Click the OK button to save the host key.
After a while, you can see that the connection is established as follows. You
can now transfer large files to
/home/work/ or other mounted storage folder
with this SFTP connection.