procfs (or the proc filesystem) is a special filesystem in UNIX-like operating systems that presents information about processes and other system information in a hierarchical file-like structure

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How do I source another process's environment variables?

If I examine /proc/1/environ I can see a null-byte-delimited string of process 1's environment variables. I'd like to bring these variables into my current environment. Is there an easy way to do ...
4
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1answer
39 views

Does pipe's link target exist somewhere in the filesystem?

I'm talking about this: $ readlink <(echo test) pipe:[80076194] Is pipe:[80076194] a path to the target or just indication that the file descriptor is connected to the pipe and doesn't exist in ...
1
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1answer
43 views

how to determine the max user process value?

Which value is correct?(or they are all correct, but which one will take effect?) $ cat /proc/sys/kernel/pid_max 32768 $ ulimit -a |grep processes max user processes (-u) 77301 $ cat ...
4
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2answers
45 views

Portability of file descriptor links

I've always wondered this but never took the time to find out, so I'll do so now - how portable is the usage shown here of either /proc/$$/fd/$N or /dev/fd/$N? I understand POSIX guarantees /dev/null, ...
47
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3answers
2k views

What happens when I run the command cat /proc/cpuinfo?

What happens when I write cat /proc/cpuinfo. Is that a named pipe (or something else) to the OS which reads the CPU info on the fly and generate that text each time I call it?
3
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1answer
47 views

Whats the correct value to base the maximum number of CPU's to sched_setaffinity to?

I have some confusion as to whats the correct value to use for the number of CPU's I can use to make a CPU_SET for a sched_setaffinity call on my system. My /proc/cpuinfo file: processor : 0 ...
3
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1answer
55 views

Kernel /proc ipv6 settings precedence

I'm about to connect our network to the IPv6 Internet and need to control the kernel ipv6 settings found under /proc. I know there are configurations for each interface, for all interfaces, and the ...
3
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1answer
91 views

Does “syslogd” cause “cat /proc/kmsg” not to work properly?

I'm using cat /proc/kmsg to determine which process and file was involved in certain disc writes. I'm using the method given in this answer. But when I use cat /proc/kmsg, the output doesn't always ...
2
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1answer
196 views

Accounting for /proc/net/dev reported traffic

I noticed that according to /proc/net/dev I am constantly receiving around 6Kb/s on my wireless usb interface. But I can't account for anything even close to that with the individual connections that ...
2
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0answers
42 views

/proc/self/maps - 3rd mapped piece of file?

I'm running Arch linux on my laptop, which is kernel 3.12.9 right now. Something has changed about the way the kernel maps in a dynamically-linked executable and I can't figure it out. Here's the ...
1
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1answer
62 views

Do VmPeak & VmHWM have any measurement periods?

While reading kernel documentation I came across VmPeak & VmHWM, and it's a bit unclear to me. VmPeak in /proc/<pid>/status is described to be peak virtual memory size. Peak for what ...
0
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2answers
76 views

How to get total disk read/write in bytes per hdd device from /proc

How to get total disk read/write in bytes per hdd device? for example if i have sda, sdb, and sdc, is there any file on /proc that i could use similar to /proc/net/dev for networking?
2
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3answers
73 views

How to find out easily whether a block device (or a part of it) is mounted somehow

I want to know what the easiest way is to determine (without root privilege) whether a block device (say sdb) or any part of it is mounted (and which part of it). Checking /proc/mounts for sdb is not ...
2
votes
1answer
57 views

What is the Inverse of Idle in /proc/stat?

/proc/stat/ includes the following fields: "user", "nice", "system", "idle", "iowait", "irq", "softirq", "guest", "guest_nice", Which subset of those fields + idle accounts for 100% CPU? Is there ...
1
vote
2answers
87 views

processor(s) statistics that is one day old

I already know how to use grep -w cpu /proc/stat in order to get the cpu stats and identify the user mode. Percentage wise, I just divide it my the total time from the /proc/uptime. However, how can ...
0
votes
1answer
195 views

The amount of time since the system was last booted [duplicate]

I have used both uptime and cat /proc/uptime commands. I know the idle time in the later can be greater than running time (multiprocessors). However, when I add both running and idle times, and ...
3
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2answers
1k views

“echo 3 > /proc/sys/vm/drop_caches” - Permission denied as root

I am currently having some issues with the cache. It is a little too much right now so I wanted to clear it. I googled and found this little command: sync && echo 3 > ...
0
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1answer
173 views

root permission denied on /proc/1/exe

I just performed a fresh ubuntu install and i am seeing the following in lsof: userA@az1:~$ lsof COMMAND PID TID USER FD TYPE DEVICE SIZE/OFF NODE NAME init 1 ...
8
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2answers
316 views

Determine if a specific process is 32- or 64-Bit

Given a 2.6.x or newer Linux kernel and existing userland that is capable of running both ELF32 and ELF64 binaries (i.e. well past How do I know that my CPU supports 64bit operating systems under ...
2
votes
2answers
217 views

Busybox ash script does not exit cleanly after executing cat; unable to get exit code

Consider the following script wrapcat.sh (a wrapper for cat) for illustrative purposes. It is run with busybox (ash) in an embedded Linux 2.6 box. #!/bin/sh cat $1 Under certain circumstances, this ...
2
votes
2answers
150 views

where does lspci gather its information from?

In kernel.org's documentation on proc I found "[The latest version of this document is available online". There I says: "… lspci is a synonym for cat /proc/pci". Which isn't the ...
4
votes
2answers
114 views

UUID in /etc/mtab

In some versions of Ubuntu. Disks are mounted by UUID. in My machine, /proc/mounts /dev/disk/by-uuid/UUID / ext4 rw,relatime,errors=remount-ro,barrier=1,data=ordered 0 0 /etc/fstab UUID=U-U-I-D ...
4
votes
1answer
59 views

Why is UID information not in /proc/X/stat?

This is a silly question for the sake of academics; I know where to get the UID information if I need it. According to the proc(5) man page: /proc/[number]/stat Status ...
6
votes
1answer
421 views

How do I know if a serial port is actually transmitting data, without opening the device?

I have a high-availability cluster (Heartbeat) connected via serial line and two ethernet NICs. I'd like to set up a monitoring script capable of recognizing disconnected serial line (basically the ...
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0answers
63 views

Value of /proc/sys/kernel/hostname

I've set computer hostname in /etc/hostname a while ago (also there are record in /etc/hosts). Everything worked fine, but recently I've noticed that value of hostname (and /proc/sys/kernel/hostname) ...
3
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1answer
92 views

Is there a way to show all flags in /proc/mounts?

Some filesystem flags seem to be hidden in /proc/mounts, depending on whether they are defined as defaults. Is there a way to show all flags in /proc/mounts, also including the default ones? And if ...
1
vote
1answer
406 views

Modify 'Soft Limit' of 'Max processes'

I tried ulimit -u 2000 and ulimit -Su 2000 to modify the 'Max processes', and started up my program, but failed. I found file '/proc/pid/limit' is still: Max processes 1024 ...
6
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2answers
132 views

Which of proc, sys etc. should be bind-mounted (or not) when chrooting into a “replacement” distribution?

This answer to another question basically boils down to chrooting into another Linux distribution in order to mainly use that as a replacement to its too restricted (but irreplaceable) parent. The ...
2
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2answers
67 views

Detecting Kernal Thread on Older Kernel Version

Looking at the proc man page (http://man7.org/linux/man-pages/man5/proc.5.html) it is possible to detect which processes are kernel threads in /proc/<pid>/stat by looking at the flags value ...
3
votes
3answers
170 views

Command line options of rackup are not shown in ps output or procfs

As you know if you wish to get command-line runtime arguments for running command you can parse ps -e or /proc/<pid>/cmdline. But I have encountered issue when this method returns only command ...
1
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1answer
132 views

Ubuntu: /proc/pid/comm file missing

On my development box, under /proc/[pid]/ there is a file called comm containing the name of the executable for that process. I use this to validate the process to which I am sending a signal. On our ...
4
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1answer
522 views

Notify of changes on a file under /proc

I have written a small 'daemon' in bash that will switch to the headphones if they are detected, and if not, switch to an external USB speaker with PulseAudio. What I'm looking for is some way to get ...
6
votes
1answer
510 views

sysctl: /proc/sys/net/ipv[46]/conf/: what's the difference between “all”, “default” and “eth*”?

In sysctl, the /proc/sys/net/ipv[46]/conf/ keys have the following subkeys: all, default, and a key for each network interface. For example, on a machine with a single network interface eth0, it will ...
3
votes
2answers
61 views

How proc gets updated about the devices [duplicate]

If i do cat /proc/asound/cards it lists all the sound card details from where proc gets this information.This file is continuously updating what if i want to make a manual entry
6
votes
2answers
377 views

/proc/sys vs /sys/modules/mod/parameter

I've been wondering for last few days how exactly does it work. We can set kernel runtimes parameters using sysctl or echo boolen 1> /proc/sys/module/exactParameter but in ...
2
votes
1answer
476 views

/proc/cpuinfo showing zero cpu clock speed

I saw an interesting issue where the cpuinfo file from /proc filesystem shows the cpu clock speed as zero. It is a physical host with no virtualization. Can someone explain to me some probable reasons ...
3
votes
1answer
321 views

Is there an easy way to log all commands executed, including command line arguments?

I am trying to find how to log a specific instantiation of rrdtool to see whether the path it is receiving is incorrect. I know I could wrap the executable in a shell script that would log the ...
2
votes
2answers
75 views

How to get environmental variables of a very short process?

I have a very short process for which i want to check the environmental variables for debugging purposes. The process is instant from a human perspective. The example illustrates it better. Example ...
3
votes
1answer
211 views

How to get the actual keyboard device given the output of /proc/bus/input/devices?

When I run: cat /proc/bus/input/devices ...I receive the following output: ... I: Bus=0003 Vendor=040b Product=2000 Version=0110 N: Name="Generic USB Keyboard" P: Phys=usb-0000:00:1d.0-1/input0 ...
0
votes
1answer
103 views

How are username, date and time are registered in kernel

How is the date and time of kernel compilation registered in kernel image? cat /proc/sys/kernel/version #35~precise1-Ubuntu SMP Fri Jan 25 17:15:33 UTC 2013
3
votes
2answers
128 views

Determining if a file system object is a procfs/sysfs/etc. “virtual file” which doesn't report its length correctly

Some kinds of pseudo-files, like many in the procfs and sysfs virtual file systems, have no file size (stat returns st_size == 0) and do not support SEEK_END in fseek. These file system objects, such ...
5
votes
2answers
293 views

mount options shown in /proc/mounts

IIRC then the mount options shown in /proc/mounts have changed. Some time ago acl and user_xattr were shown, now it seems that only noacl and nouser_xattr are shown if these features are turned off. ...
2
votes
3answers
265 views

files in /proc/$PID (e.g. ssh-agent, Chrome) are not owned by user but by root

I am just answering another question here :-) and thus had a look – wanted to have a look at /proc/$PID/fd of ssh-agent in order to find out which socket it uses. But I can't. I am quite surprised to ...
3
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1answer
545 views

Explain EV in /proc/bus/input/devices data

Can anybody explain to me what the EV value in /proc/bus/input/devices is? The keyboard always has value 120013. Why?
22
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2answers
1k views

How frequently is the proc file system updated on Linux?

How frequently is the proc file system updated on Linux? Is it 20 milliseconds (time quantum)?
1
vote
1answer
388 views

How to clone a read-only portion of /proc file system

The problem with reading /proc file system is that it is not atomic. I tried using a library (procfs in Python) that wishes to read it, but it has glitches about 5% of the time because the process ...
1
vote
1answer
195 views

Do kernel counters for jiffies in state exist in Linux?

I am looking to get time/jiffie stats on the state of a daemon process. The states I'm referring to are mentioned in the Linux Kernel Proc Filesystem document. Running, Sleeping, uninterruptible ...
8
votes
2answers
574 views

A hidden process, what it is?

[root@datacenteronline ~]# ssh root@192.168.1.172 Last login: Wed Apr 17 09:55:45 2013 from 192.168.1.187 [root@localhost ~]# ls /proc/ | grep 2266 [root@localhost ~]# cd /proc/2266 [root@localhost ...
1
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1answer
112 views

Looking for /procfs documentation, describing values and units of measurement

Surprisingly, comprehensive documentation for /procfs is hard to find. For my specific question, I am looking at: cat /proc/1/statm (let's use pid=1 because it seems to be always there). I just ran ...
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0answers
70 views

Viewing shared segments created by shmget

I'm trying to "visualize" shared memory between two processes. I've created a little server-client example where the client writes some data to a shared memory location and the server reads from it. ...