www/content/services/shell.md

title	geekdocDescription	weight
Shell Accounts	burble.dn42 Shell Services	60

burble.dn42 provides shell accounts on the following servers:

• shell.fr-rbx1.burble.dn42
• shell.ca-bhs2.burble.dn42
• shell.us-nyc1.burble.dn42

Accessing the Service

The shell service imports user information from the dn42 registry allowing any MNTNER with an SSH auth method to log in to the servers. Usernames are constructed by lowercasing and removing the '-MNT' suffix.

{{}} FOO-MNT

mntner:             FOO-MNT
auth:               ssh-ed25519 xxxxxxxxx

Log in using the key specified in the auth method:

ssh foo@shell.fr-rbx1.burble.dn42

{{}}

Your home directory is created automatically on first access and will then persist across logins.

Key Services

Installed Packages

A broad set of command line tools, applications and games are available; the aim is to provide a comprehensive environment that is useful and fun to tinker with.

The current set of packages can be found in the shell config repo:

• https://git.dn42.dev/burble/config-shell/src/branch/main/roles/user_apps/tasks/main.yml

Requests for additional packages are welcome, please raise these as issues in the repo.

Webserver

The shell servers include a webserver with user directories (~/public_html/) and CGI (~/public_html/cgi-bin/) enabled. The webserver is accessed over https and has a dn42 certificate auto-renewed from the ACME service.

• https://shell.fr-rbx1.burble.dn42/~<username>/
• https://shell.ca-bhs2.burble.dn42/~<username>/
• https://shell.us-nyc1.burble.dn42/~<username>/

{{}} Remember that any files need to be accessible by the webserver which runs as user/group www-data/www-data; CGI scripts must also be executable. The default umask of 077 means that the webserver won't be able to read your public_html folder or any files within it without changing permissions.

A simplistic approach would be to make your home directory, and public_html directory world readable:

chmod a+x ~
chmod -R a+rX ~/public_html
chmod -R a+rx ~/public_html/cgi-bin

A more secure way of allowing access would be to use posix ACLs:

setfacl -m "u:www-data:x" ~
setfacl -Rdm "u:www-data:rX" ~/public_html
setfacl -Rdm "u:www-data:rx" ~/public_html/cgi-bin

{{}}

Scratch Area (fr-rbx1 only)

A large storage area is mounted on to /scratch

/home disk space is limited, so /scratch may be used for additional space or if you don't want to use /home. If you want to use the scratch area it is recommended to create your own directory (named after your username) and then store all your stuff in the new directory; this will help prevent clutter.

{{}} Note that the storage for /scratch is nfs mounted across dn42 so performance will be variable. {{}}

Changing Shell

The registry import process currently limits the initial shell to /bin/bash and currently this cannot be changed. If you want to use something different, just exec to the new shell in your .profile or .bashrc.

{{}} Example .bashrc line for zsh:

if [[ $- == *i* ]]; then exec /usr/bin/zsh; fi

{{}}

Cron, Batch and Services

Cron and other batch or long running tasks are ok, but be a nice neighbour and prioritise other users' interactive use.

Schedule crons to run at random or obscure times to avoid stampeding herds and control your resource usage using tools like nice and ionice.

Clearnet

Clearnet access is provided. Rate limiting allows for a small amount of burst traffic, but then bandwidth is quickly limited to 10mbit/sec. In general, you should be better off using your own clearnet access for large downloads.

Performance Monitoring

The shell servers are monitored using netdata and prometheus, with performance graphs available in grafana.

The netdata dashboard is also directly accessible:

• http://shell.fr-rbx1.burble.dn42:19999
• http://shell.ca-bhs2.burble.dn42:19999
• http://shell.us-nyc1.burble.dn42:19999

Acceptable Use

The objective of the burble.dn42 shell service is to provide a free, open, and fun environment for dn42 users. The services are provided for your benefit so please be considerate in your usage and remember that abusing the service just spoils it for everyone else.

See also the main Abuse Policy.

Source Code and Configuration

Configuration for the shell servers is maintained in a git repo:

• https://git.dn42.dev/burble/config-shell

The repository may be used for raising issues or requesting additional software to be installed.