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#1 2011-05-08 07:57:34

awayand
Member
Registered: 2009-09-25
Posts: 398

Detective support: track file accesses by processes

Hello everyone,

I am trying to become a better detective at finding out what's going on under the hood of my arch linux. Can you help me? I am compelled to ask a general question hoping for an all-encompassing answer, but that is unlikely to happen, so let me do this step-by-step by asking real-life questions with concrete issues I am having and maybe over time I can master this thing.

I recently asked myself how to handle automounting devices like usb sticks that I plug into my pc. So after browsing through the forums, I decided udev was too complicated for me for now, I needed a solution fast, so I settled with pcmanfm. So here's what I did:

$ pacman -Ss pcman

... to search my program of choice, then a quick

$ pacman -S pcmanfm

...installed the program for me.

Then I launched the program, and it opened a window:

$ pcmanfm

I checked the preferences to make sure it worked the way I wanted it to, which is automount everything I plug in. The next issue I had was trying to figure out how to launch pcmanfm to automount my devices automatically, but without opening up a file manager window like it did because I am already using rox. So I did a

$ man pcmanfm

...which turned up nothing. Fair enough, let's see if there is any README or /usr/share/doc-type documentation for this thing out there:

$ pacman -Ql pcmanfm

...nothing, just an /etc/xdg/pcmanfm/default/pcmanfm.conf. Ok, let's try

$ pcmanfm -h

...fair enough, so I can start pcmanfm in "daemon" mode, and make it not "be" a desktop. I would expect "daemon" mode alone to be enough to not show a window upon startup, but when I launch

$ pcmanfm -d

...I still get a window so in the end I settle with the following in my ~/.xinitrc file, right before the line that launches my window manager (awesome):

pcmanfm -d --desktop-off

My next problem was the pcmanfm wasn't mounting the volume, even after I clicked it. I saw some debug messages in the terminal saying that pcmanfm was doing stuff, so I got the idea to create a /media directory, and magically it worked. However, creating this media directory was a pure coincidence based on intuition.

Now if I was just a user trying to make things work, my efforts would stop here, but I am trying to learn so here is my first question to you:

Is there a way I could have found out exactly why pcmanfm wasn't mounting? In other words, is there a way to monitor an application and its access requests to the filesystem?

If there was such a thing, it would help me tremendously because I could have found out that pcmanfm was trying to access /media, and I could also find out if I can use the pcmanfm.conf file in my home directory and in what exact location and what name (~/.pcmanfm.conf or ~/.config/pcmanfm.conf) as at the moment pcmanfm doesn't seem to pick up any of these locations.

Thanks for your help!

Last edited by awayand (2011-05-08 07:58:26)

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#2 2011-05-08 08:12:44

ewaller
Administrator
From: Pasadena, CA
Registered: 2009-07-13
Posts: 19,728

Re: Detective support: track file accesses by processes

try strace


Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
---
How to Ask Questions the Smart Way

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