Calyx blog

Let’s just assume that you have some important stuff being done on your server. A computation running, like I do, something getting compiled for a long time, or whatever else you might need. You don’t want to be sitting all the time, sshed in and running tail -f dump.log So you think to yourself: “If only I could have this file posted to a website so I could just check it here and there from my cellphone”. That’s your wish (believe me — I can read minds). Well, I had the same wish a while back and this little script came out of it.

Of course, I like to at least try to code stuff up, instead of just writing to Santa. However, I usually go and try to generalize a bit. Let’s say that I want to monitor a few files or outputs of various commands at the same time. Moreover, let’s say I want to add these things as I go. Enter
remotespy.

Remotespy is a script that parses a list of commands to run and compiles their output into a HTML webpage. The page is then saved to a local folder, e.g. public_html. Additionally, it can be scp-ed to a destination of your choice. This is useful if your “workhorse” server doesn’t have a http server setup, but you do have some other place to post your output to.

The syntax is simple:
remotespy COMMANDFILE HTMLFILE"
The spirit of the command file is similar to the one of crontab scripts: every line represents a command that is run. Syntax of every
line is:
TITLE ## COMMAND ## COMMENT

A sample script looks like this:
Hostname ## hostname
OS ## uname -orpi ## OS version
Disk ## df -h ## Free disk space
Top ## top -b -n 1 -i ## Process state
Vmstat ## vmstat ## Memory state

Every command is run as-is and its output captured and formatted into HTML. The HTML code is hardcoded in the script, but, script being a script, it can be easily edited. To make remotespy into a tool satisfying the initial desire of remote monitoring, it can be paired with cron and ssh to periodically run commands from the script and send the files to a (remote) public_html folder which is available to the internets. For the SCP upload to be useful, you should set up a ssh key pair between the source server (one running remotespy) and destination http server. These two articles can help if you don’t know how to do it yet:

• http://www.linuxjournal.com/article/8600
• http://mindspill.net/computing/linux-notes/ssh-or-scp-without-password.html

The refresh meta tag is also set for the page so you don’t have to refresh the page manually to check if cron ran the command.

Remotespy was written in Python and tested on versions 2.4 - 2.6. I don’t know how far back the compatibility actually extends. I like to use it as it allows me to edit the command script without having to reinsert anything into cron. The HTML output is simple enough to be quickly read from mobile devices so I can check on my simulations state whenever I feel like it. You can find it in my Mercurial repository among other scripts I’ve written:
http://bitbucket.org/mbudisic/cl-goodies/src/tip/remotespy
(The repo name was taken from el-goodies collection for Emacs).

Let me know if you have suggestions for improvements. Future versions should probably migrate from “commands” to “subprocess” Python module. Also, I might make remotespy into a daemon to make it cron-independent, but that’s a low-priority for me. This does the job well. If you would like to extend remotespy, please let me know, I’d love to hear from you. If once wasn’t enough, you can read this post at http://mbudisic.wordpress.com/2009/04/03/monitoring-from-afar/ too.