14. Sharing on the net

status: barely started - just a placeholder

14.1. Motivation and plan

It is important to be able to flexibly put files and documentation in networked places where you can get to them from different locations. This also lets you distribute data files, source code, documentation to other people.

We will discuss a bit of the picture of what’s available. This changes quite a bit with time, so I will mention that I last proof-read this introductory section on 2020-05-18. This will allow you to see how obsolete this information is.

14.2. Static files

14.3. Content management systems

14.4. Sharing the vieweing of active terminals

Tools are: screen, tmux, teleconsole, tmate.

GNU Screen, https://www.gnu.org/software/screen/

The oldest of these programs, screen was posted to comp.sources.unix in 1987 1. Originally focused on multiplexing a single physical terminal, today it is used more for its remarkable ability to stash the session it was in even if the connection dies. You can then pick this session back up from another login session coming from a completely different place.

If you are used to using Control-a (the control key and ‘a’ at the same time) to go to the start of a line (and you should be used to that) you should bind a different “hot key” in your .screenrc - I use the backtick character, for example, so my ~/.screenrc file has this line: escape `` but in the description below I will assume Control-a.
Type screen.
Type a command that puts some text in your screen.
Create a new window with Control-a Control-c - you will not see the original one anymore.
Switch between them with Control-a n.
Play with creating new ones, switching between them, and closing some.

Now for the session detachment:

In your original screen session run a long-running job. This could be a scientific simulation that you do not want interrupted when you disconnect, or a long measurement from some lab equipment. Or a trivial shell script like:
```
for i in `seq 1 1000`
do
    date --iso=seconds
    sleep 30
done
```
Log in to that same host from another terminal window (or from a different computer altogether). If you are curious, keep your eye on the original screen: it will be interesting.
Type screen -Dr (-D will detach the original screen, and -r will reattach it here.
Learn more keybindings (and how to create your own) with man screen

This has all been individual. Now we’ll quit all those screen windows and create a new screen to share with other people! This is a good way to tutor people and watch what they are doing.

Create a new screen session with just one window and nobody attached to it:
```
screen -d -m -S one-dude-sharing-with-others
```
In another terminal list existing sessions and then attach to our new session with:
```
screen -ls
screen -x one-dude-sharing-with-others
```
and create a second window with Control-a c and run some unique commands in it, like banner first dude
In another window attach to it in the same way and cycle through windows with Control-A n until you find one that does not have the first dude’s stuff, and run a unique command in that shell, like banner SECOND dude
Go back to the first window, cycle through windows until you find what the second dude did.

Note

Sharing that screen with another login name has some extra subtleties which are described in the Network Security Toolkit wiki

tmux

Another terminal multiplexer of more modern vintage than screen. tmux offers many of the same features. It multiplexes a single terminal, it allows detaching and reattaching. The individual bindings and commands even look similar to those in screen, although the default prefix is Control-b instead of Control-a.

teleconsole

teleconsole allows you to cast your terminal session to a public web page. This is a good way to give public demonstrations of shell procedures and of any programming that can be done in a single window.

Using it is almost too easy: run teleconsole and it will start a new shell that is shared on the web. You will be given a friendly message with a URL for the session, something that looks like this: https://teleconsole.com/s/c5c10064548622796ef26b189635824f7644dbf6

You just announce this URL to your “guests” and start typing. The only security is the obscurity of that URL. Also note that this program relies on some organization running that teleconsole.com web site, otherwise you would have to set up a server yourself.

A lengthier description can be found at https://www.2daygeek.com/teleconsole-share-terminal-session-instantly-to-anyone-in-seconds/ and a very detailed manual is at https://gravitational.co/teleport/docs/admin-guide/

tmate

tmate started as a fork of tmux, and it added a rather cool feature for sharing with remote users with ssh instead of through the web. Right after you start tmate it gives you a line like this one:

[tmate] ssh session: ssh RCJWHsWqejdwsTaHb69GXzDXG@sfo2.tmate.io

and you can just tell people to paste that ssh line in to their own terminal. It is it eerily useful to see this mirroring of characters and screen info as it gets typed. Once again this relies on someone having set up a public ssh server (in this case at tmate.io).