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diff --git a/sites/pmikkelsen.com/plan9/mounting-9p-over-drawterm.md b/sites/pmikkelsen.com/plan9/mounting-9p-over-drawterm.md new file mode 100644 index 0000000..414b9f2 --- /dev/null +++ b/sites/pmikkelsen.com/plan9/mounting-9p-over-drawterm.md @@ -0,0 +1,58 @@ +# Mounting a 9P connection over drawterm + +I sometimes use drawterm on linux to connect to my 9front server. +While it is possible to access the host system's files under `/mnt/term`, there is no builtin way to access the remote system's file under linux. +Now, why would anybody want to do this? +In my case, I often want to write some code under 9front, but for languages which aren't supported such as prolog in this case, so there are three options as I see it: + +* Store the files on the host machine, and access them under `/mnt/term`. +* Store the files on the server and somehow mount the server's filesystem on the host. +* Store the files on a third machine that both the host and server can access. + +Option number two seems best for me, so I asked around and it seems like the best tool to mount a 9P connection on linux is [9pfs](https://github.com/bunny351/9pfs). + +## How it works + +Before I could mount the connection, I had to serve it somehow. Normally I already serve 9P directly from my server's filesystem, but that requires some +authentication that 9pfs does not support, so I had to serve it without authentication. +Serving directly to the internet without authentication is of course pretty dumb since everyone can then access my files, so thanks to a hint from hiro, I figured +out that it is actually possible to use the host's network stack on the server by binding `/mnt/term/net` over `/net`. + +I'll just show the final script below and explain it afterwards: + + #!/bin/rc + + rfork n + bind /mnt/term/net /net + aux/listen1 -t tcp!*!12335 /bin/exportfs -r / & + os mkdir -p /tmp/drawterm + os 9pfs localhost -p 12335 /tmp/drawterm + +So the first thing that happens is that I bind the host's network in, and from that point on, every network connection in this namespace actually goes out +from the host instead of from the server! + +Then `exportfs` is started and it is serving the `/` directory over 9P at port 12335. +The `os` command runs a command on the host, so it just creates the folder that the system will be mounted to, and then uses `9pfs` to actually mount it. +The nice thing here is that `9pfs` just connects to localhost. + +## Using it + +As I said in the beginning, I did this to be able to edit files on the 9front server, and run compilers/interpreters on linux. +The `os` command goes a long way, but the following script makes it even easier (I have this installed as `linux`): + + #!/bin/rc + + dir=/tmp/drawterm/`{pwd} + os -d $dir $* + +This means I can just go into any directory on the server, type `linux ghci` and I get a haskell repl running in the correct directory, as seen in the gif below. + +[![An animated gif showing ghci loading a file on the 9front server][1]][1] + + +## Final notes + +The bind net trick still blows my mind a bit, since it is so trivial, yet so powerful. It is also fun to think about how one would do this +on other systems than plan9, which I can't even imagine. + +[1]: /images/linuxreverse.gif |