SSH and servers

Overview

You can connect to our servers over SSH in order to run programs, manage files, and change your password.

Clients

You will need an SSH client – Mac and Linux come with ssh in the terminal; for Windows, you can enable OpenSSH in Optional Features, use a Linux distro in WSL, or install a Windows client like PuTTY.

Alternatively, you can access a web-based terminal in your browser.

Passwordless SSH

Passwordless SSH is often a point we get asked about.

There are a number of reasons why your passwordless ssh setup might not be working but by far the most common (and the hardest to detect on the client side!) is incorrect permissions on your .ssh directory. Because the authorized_keys file contains sensitive information it must not be readable by any other user. Therefore you should ensure that the file $HOME/.ssh/authorized_keys have permissions -rw------- (i.e. 600). 660 (-rw-rw----) will not work even if you are the only member of the group that owns the authorized_keys file. The same caution about permissions applies to the .ssh directory itself.

Available hosts

Shell

shell.srcf.net

Our main server is pip. This is a general-purpose machine for running software. It has the following SSH fingerprints:

DSA  MD5:12:8f:8a:1c:e4:f7:a2:9d:80:a3:ef:85:f8:79:a4:ed
DSA  SHA256:fshymFC90Vd0BrlFnAdilNKSWNsoQVI7qa8/GIMBqtw
RSA  MD5:4d:da:7f:b2:99:9d:42:8b:10:b4:e5:37:d5:bd:43:b4
RSA  SHA256:ud4XwVhosGW3oHZ2POzW4oz0zGC2y7JWLGOM1dbIqZw

Web

webserver.srcf.net

Web applications should be run from sinkhole, our webserver. This includes Apache, our server software of choice, along with custom backend servers which Apache can proxy to. Sinkhole has SSH fingerprints as follows:

DSA      MD5:20:28:75:a4:c5:0b:08:47:c5:ae:f8:8c:21:01:1a:00
DSA      SHA256:iyt8GRgVBQSNyaH/yX7QZuFODMzfpsO9xV7UnaxICLI
ECDSA    MD5:90:78:92:7b:1e:4e:51:22:30:3b:e0:dd:97:9c:aa:e4
ECDSA    SHA256:G1glvFC2H4VR9mA1RkJCRVVyLB6e/LarI+8ZUFRGds8
ED25519  MD5:55:2e:b8:bb:53:79:9a:62:0f:62:24:e3:8d:7f:87:62
ED25519  SHA256:WalyNfnZm6yuIhMhe6kj17NikSK8LuC2I6iggWYTKcY
RSA      MD5:76:aa:f1:63:ec:ca:ac:97:fb:05:35:3c:c7:8f:55:ff
RSA      SHA256:DSC30UdUoQNYWhwU4icuPOyrDC9xVjsnKbRC3Mz9RZM

Games & others

doom.srcf.net

If you’d like to run a game server or more CPU-intensive application, please use doom, which has fingerprints:

ECDSA    MD5:74:52:6e:52:d7:07:51:9e:93:12:51:82:8c:b4:ec:0a
ECDSA    SHA256:QdTm7ECl0KObTodBBpY6Qs57PFmr3MHvQfT50IbKa3U
ED25519  MD5:49:d8:e6:67:19:1c:c5:ed:12:de:3a:64:91:95:4c:9d
ED25519  SHA256:kh1Sr6Nrlp/vK9ijKZ43/IQ2tqdPzY/fnZdnGBIKgIM
RSA      MD5:f1:ee:8c:a7:7a:cb:f7:c7:dc:c5:7e:56:9a:83:f5:bc
RSA      SHA256:c1dlaFnPyJ44CnjZIeV6zLHQCPlIH9Og0K3dL16XGfo

Troubleshooting

Unsupported term-type environment variable

If the terminal behaves incorrectly on certain keypresses - such as by outputting weird glyphs, or by not removing characters when inputting a backspace - then it is possible ssh has misconfigured the TERM environment variable.

This can be checked by running toe -a | grep $TERM. (toe -a lists all supported values for the TERM variable, and | grep $TERM performs a search within toe's output to try to find your session’s value of $TERM). If running the command shows no output, then your value of TERM is unsupported.

You can temporarily select a more general terminal type (xterm-256color should work) for your session by setting the TERM environment variable when running ssh:

TERM=xterm-256color ssh ...

To correct this persistently, run the following command (on your device):

infocmp -a $TERM | ssh <Your CRSid>@shell.srcf.net tic -x -

This will install your device’s terminal-type to your account’s home directory (inside ~/.terminfo/). You will not need to make any manual changes to contents of this directory. Your terminal should now work correctly for all subsequent sessions.

Last modified on Sunday Oct 15, 2023 by Seliksi