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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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 ...
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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 ...
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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 ...
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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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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) ...
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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 ...
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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 ...
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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 ...
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Detecting kernel thread on pre-3.0 kernels

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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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2answers
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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
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/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 ...
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1answer
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/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 ...
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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 ...
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2answers
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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 ...
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1answer
502 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 ...
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1answer
157 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
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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 ...
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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. ...
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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 ...
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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?
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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)?
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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 ...
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419 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 ...
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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 ...
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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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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. ...
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1answer
152 views

Determine how much a process is using each disk?

How do I tell how much load a particular process is contributing to each of several available volumes/mounts? It seems that dstat only shows aggregate stats across all processes per disk, and iotop ...
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iotop but for particular disk?

Is there a tool like iotop but for monitoring IO on specific volumes? (Or perhaps I missed a way to filter iotop?) If not is there any way to get at this information via (say)/proc? (dstat etc. ...
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Arch linux : pacman does not work when chrooting

I have Ubuntu installed on my computer. I decided to install Arch linux, but I skipped the part about Grub installation as it is already installed. Seeing that Arch does not show up in Grub's menu ...
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Is it possible to tell df to use /proc/mounts instead of /etc/mtab?

Installing gentoo in chroot I found that commands like mount and df doesn't work: they try to read file /etc/mtab (which of course is empty). Can I (for future use) setup or even recompile them so, ...
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/proc/net/wireless does not show values unless run as root

cat /proc/net/wireless does not show statistics for wireless devices unless it is run as root, even though the permissions on the file are 444. The same seems to apply when accessing statistics via ...
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Why do I have four CPUs listed in /proc/cpuinfo?

When I bought my Lenovo Thinkpad 520, it had Windows installed. I promptly cleaned that out and installed Fedora 16. I recently visited the /proc/cpuinfo and, much to my surprise, discovered that it ...
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how long use of linux? [duplicate]

/proc/uptime shows how long the system has been running since the last time I turned it on. Is there a way to determine the total amount of time the system has ever been on since I first installed it? ...
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583 views

vmstat on virtual machine and large values

Hi I'm using vmstat to track machine performance during some tests (jmeter). This is virtual machine running on a big machine where lots of other virtual machines are installed (about 20 virtual ...
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When was a process started

To know when was a process started, my first guess was to check the time when /proc/<pid>/cmdline was written/modified the last time. ps also shows a START field. I thought both of these ...
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1answer
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Very large values for utime and stime for foo. Is foo still running?

I am running a program foo It has been running for close to 30 days now (even more) Until around 10 days ago (I cannot be very exact) it used 100% of one cpu on my dual core laptop (it was at the ...
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2answers
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No /proc in a Busybox-based embedded Linux distribution

I am making an embedded Linux distribution and my board is a Raspberry Pi. My kernel version is 3.2.27 without initramfs and my root file system as follows: /lib /* contains ...
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1answer
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“ps” output and comments

I'm pretty sure you cant do this but maybe someone has some weird hack... Is there a way to get comments (#blahblah) to show up in ps output? My problem is that i have a script, lets call it ...
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Linking /proc/mnt to /proc/mounts

I understand that /proc filesystem reflects the output of various processes. Unfortunately, I have a propietary (romdump) binary that expects the mount table to appear as /proc/mtd, while my Android ...
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1answer
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Timestamp of socket in /proc/<pid>/fd

If I list /proc/<pid>/fd I see a number of entries for sockets. These entries have timestamps. At first I thought they were when the socket was created. But it doesn't always appear to be the ...
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Is there a faster interface for info from /proc/net/tcp?

Given a linux TCP socket's inode (obtained via /proc/<pid>/fd), is there a faster way to look up the information that I can get from /proc/net/tcp about this socket? I have written a ...
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About sector and blocks, and a little confusion in /proc/diskstats

I've been studying about diskstats lately, and I get that the amount of hdd read comes in sectors. But in most places I've noticed that there exists a slight misunderstanding about sectors and blocks. ...
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Files bigger than max(off64_t) on Solaris, eg “/proc/../as”

How do I read or seek from a file that's bigger than the maximum off64_t? The problem arises because the address space of a process is represented in the /proc/.../as file, which is a huge sparse file ...
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1answer
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System IDLE Time > System Uptime?

I was testing out the linux api while working on something but got stuck on the following output. [Abhii@localhost net]$ cat /proc/uptime 39135.53 149657.73 As per specs the first number should be ...
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File delete versus overwrite and link at /proc/pid/fd

It is well known that UNIX systems won't actually delete a file on disk while the file is in use. So if a file is being accessed by process 1 and process 2 deletes the file using rm, process 1 ...
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When do jiffies increment? How a process runs in a jiffy?

I know that jiffies length is selected at kernel compile time and it is defaulted to 250 (4ms). Source: man 7 time - The Software Clock, HZ, and Jiffies I wonder what happens inside a jiffy. What are ...