I never really considered using proc to solve my problems. I jump to logs and such but honestly, how have I never played with proc?
this post was submitted on 20 Aug 2026
916 points (99.6% liked)
Linux
67137 readers
1018 users here now
From Wikipedia, the free encyclopedia
Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).
Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.
Rules
- Posts must be relevant to operating systems running the Linux kernel. GNU/Linux or otherwise.
- No misinformation
- No NSFW content
- No hate speech, bigotry, etc
Related Communities
Community icon by Alpár-Etele Méder, licensed under CC BY 3.0
founded 7 years ago
MODERATORS
The hand written effect make these so much easier to digest.
You used to be able to sudo cat /proc/kcore > /dev/dsp and listen to your ram
Wouldn’t that just sound like gibberish? I feel like Mike Lindell would come out of the speakers.
That sounds really interesting! I couldn't find anything else on this. Is this like pre-systemd?
The RAM whisperer.
I have some of her paper zines on my desk, warmly recommended.
Might look esoteric at first but if you think we will be using Linux at least on desktop, servers, consoles and more for decades then totally worth learning about.
Julia Evans has a bunch of these really handy cheatsheets. I have several saved that I reference semi-regularly.
Got to love UNIX's everything is a file.
ProcFS is from Plan9. https://en.wikipedia.org/wiki/Plan_9_from_Bell_Labs#/proc
Plan9 is worth a deep dive, but maybe not worth running. It is more UNIX than UNIX. (Also where UTF8 came from.)
I did not know that about plan9! /proc was one of the things I missed most when I switched from daily driving linux to daily driving osx.
Well that is retrograde of it.
Another cool thing from Plan9:
https://github.com/torvalds/linux/blob/master/Documentation/filesystems/9p.rst
I'm surprised it doesn't mention that /proc/self automagically points to the directory of the current process. So if you're writing a program, you can just look there for information about itself
Okay, this is legitimately cool as heck. This finally helps me wrap my head around the “everything is a file” concept in Linux. Of course it can just copy the executable to memory for later reference. That’s how the system would not completely have a meltdown when you do live updates.
Excellent share!
It's a bit more interesting than that...
Linux, unlike Windows, will let you delete a file that is actively in use. It removes the reference on the file system but the contents of the file won't be deleted until all file pointers to it close. In fact it will still be seen as taking up disk space until it's garbage collected (deleting a large file that's in use can be frustrating).
So the file is actually still available to that running process. If you replace it with a new executable and run that then you get the new version.
I bet this is done with inodes. Deleted files aren't truely deleted until nothing has it open and its inode gets dropped. Like ARC for files.
You can also do interesting things like overwrite a "file" (as in a specific filesystem path) with new contents while keeping anything that already has the file open on the old contents by unlinking the old inode to the path and writing the new contents under a new inode. I believe mv does this. The kind of lesser known feature that probably strikes a good balance between preventing super annoying silent errors/corruption and causing them.
Thanks for explaining, I was wondering about that.
Wait, is that why renaming or moving files on android takes forever?
No, that's because Android. It's also overlaying all filesystems to enforce stupid rules, like no files named "CON" and no files named the same in a different case (like in DOS).
Wait until you see the Plan 9 API
This is awesome, and I really no no idea about this!
I didn't know any of this. Amazing. I usually just look at /proc/net/ for routes and bonding config etc.
I know what a symlink is, but what is a magic symlink?
A symlink that has been blessed by Richard Stallman.
"Now that's a name I haven't heard in a long time" -Saint IGNUcius
Anyone else getting turned on rn?
load more comments
(1 replies)
If you delete a file that's still open by the app, the link in proc will still exist and you can copy the file back out of proc.
load more comments
(7 replies)
Also known as zombie files. If you are unlucky they can take up all space on a drive, or even tmpfs (so your ram) and you can't easily find them. At least until you end the right process or restart.
Had that happen once and had to write my own script to trace it to the log of an open terminal emulator tab that had billions of lines.
Great tips! Although if i may 🤓 just a little for the top right, it works because what you deleted isn't the binary, it's the pointer that points to the binary's location. The data is still exactly as it was before "deletion"; the symlink is simply a copy of the original pointer's info; and I'm speculating that the existence of any pointer prevents the system from recycling those addressed bits.
load more comments
(1 replies)
Do you know how to build portable executables?
configure --prefix=/proc/self/pwd
It even works in .so files and libtool.
load more comments
(8 replies)
I’m aware of /proc but usually use lsof to find open fd’s for a process.
Is one better than the other?
lsof just reads from /proc and gives you formatted output
https://github.com/lsof-org/lsof/blob/master/lib/dialects/linux/dproc.c#L297
I am saving this, both for the post AND for the comments.
I love *nix’s commitment to the bit on the core abstractions.
view more: next ›