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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Incorrect permissions on special files

I've noticed a lot of special files on Linux have what appears to be incorrect permissions: E.g.: $ ls -l /dev/fuse crw-rw-rw- 1 root root 10, 229 May 29 09:59 /dev/fuse appears writable but in ...
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Strange PFN read from pagemap

I m trying to find the physical page to which a range of virtual addresses are mapped in a piece of C code that I ve written. I m using the /proc/self/pagemap to read the mapping. I ve used the code ...
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27 views

sar command vs /proc/stat for cpu usage

I have been using /proc/stat for calculating the cpu usage. Recently I have been going through sar command for calculating cpu usage. And what I found was that their values were not related (I was ...
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2answers
28 views

Getting the original command invocation from /proc/self

I'm trying to run some startup code in all procesess via the dynamic linker. The code should do stuff based on the zeroth argument of the process. I'm getting the arguments from /proc/self/cmdline ...
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1answer
27 views

How to obtain counters for swap-in/swap-out on Linux?

I'm trying to obtain counters for swap-in/swap-out activity on CentOS 6. The intention is to feed raw data into RRDtool to generate graphs, and use it to generate alerts. I've had a look at common ...
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23 views

How to manipulate a file descriptor in another process? [duplicate]

Is there any way to manipulate (read, write, etc..) a file descriptor for any app which can be found in the path /proc/{pid}/fd? Especially for sockets. $ ll /proc/4229/fd total 0 lrwx------. 1 ...
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how to get disk read/write bytes per second from /proc in programming?

purpose :i want to get information like iostat command can get . I have already known that if open /proc/diskstats or /sys/block/sdX/stat there are information that :sectors read and sectors write. ...
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1answer
32 views

How to find the pci slot of an usb controller in Linux?

I have a nearly common Linux machine here. So, it has a PCI (*-X, etc) bus, on that some USB controllers, and I have USB devices on these USB controllers. Similar to this: $ lspci|grep USB 00:12.0 ...
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Why some shells `read` builtin fail to read the whole line from file in `/proc`?

In some Bourne-like shells, the read builtin can not read the whole line from file in /proc (the command below should be run in zsh, replace $=shell with $shell with other shells): $ for shell in ...
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2answers
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Is sysfs a strict subset of procfs? [duplicate]

Is the information that the Linux kernel provides to the user via sysfs a strict subset of the information that the Linux kernel provides to the user via procfs? If not, then which information is ...
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1answer
31 views

why do I find (under /proc/pid//fd) sockets with broken symlinks

I don't think they're closed, because I would expect that after a close() the fd would disappear, but I see a bunch of lingering fd -> socket[xxxxx] entries with broken symlinks which don't seem to be ...
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How does Linux decide the /proc/PID/stat “name” of a process?

Currently my machine has 5 processes running scripts through python, but Linux thinks only 2 of them have the name python (according to /proc/$pid/stat). That is, pgrep -af python shows: 1784 ...
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37 views

Duration of /proc/pid/stat

I have a process that starts a child process and when the child exits, scans /proc/<pid>/stat to gather some information about the CPU and memory the child used. However I am worried that I am ...
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0answers
50 views

How to get the path of a current running script file?

Knowing that program's PID, I want to list out the executable file of a running program. For binary programs, I can read /proc/$pid/exe, which is a symlink to the executable. However for scripting ...
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1answer
47 views

Get the process start time irrespective of NTP updates

I'm trying to record the start time of a process kicked off by an @reboot cronjob. I'm using ps -p $$ -o ltime= presently, but I've run into a catch. My machine (a Raspberry Pi) connects to the ...
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OOM Killer: Processes have a score of over a 1000

All top links when Googling for OOM score seem to indicate that the values must be between -1000 and 1000. I tried to verify that with a simple cat /proc/*/oom_score | sort -n | less and I ...
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3answers
49 views

Get Linux architecture from /proc filesystem

I'm writing a program in Java and I need to determine the architecture for which Linux was compiled. I need something like uname -m, but without running any program, but instead from the /proc ...
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1answer
18 views

du access failures

I ran du on a particular machine and two instances of failure: Since I ran as superuser I do understand how I can get denied. Second problem was with the proc tree: I kind of get the gist of why ...
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1answer
45 views

How can I check read permission of /proc/*/* files?

Files in /proc/ seem to be world-readable, but return permission denied: $ ls -lh /proc/5589/smaps -r--r--r-- 1 root root 0 Mar 18 13:11 /proc/5589/smaps $ cat /proc/5589/smaps cat: ...
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2answers
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Can I add to /proc/self?

I want to create a number of named memory regions in my program, and mmap them somewhere so that other processes can read them. I can't guarantee that only one instance of my program will run at a ...
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1answer
54 views

Why doesn't INotify work with `/etc/mtab` or `/proc/mounts`? [duplicate]

When I used INotify with /etc/mtab or /proc/mounts, it doesn't detect changes when things mount or unmount, even though /etc/mtab and /proc/mounts both have changed when I check manually. Why is this, ...
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2answers
38 views

Can I set my core file location without being root?

It seems strange that I need to be root in order to say "place cores in my current directory" (via cat whatever /proc/sys/kernel/core_pattern). Isn't there any user-specific override for this?
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2answers
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Awk run time error: not enough arguments passed

Here is the script: TYPE="${BLOCK_INSTANCE:-mem}" awk -v type=$TYPE ' /^MemTotal:/ { mem_total=$2 } /^MemFree:/ { mem_free=$2 } /^Buffers:/ { mem_free+=$2 } /^Cached:/ { mem_free+=$2 ...
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Why would the size of /proc/stat show as zero? [duplicate]

ls -rlth /proc/stat -r--r--r-- 1 root root 0 Feb 21 04:25 /proc/stat Although if we cat it, its got enough contents. Any help regarding this virtual FS will be helpful.
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Meaning and usage of /proc/[pid]/make-if-fail

I am currently developing inside an embedded Linux environment (kernel 3.10.0), and while goofing around in the procfs mount of the system I found that all processes present the following file in ...
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1answer
55 views

Linux Unix /proc Rename

How can I rename /proc to something else forcefully? mv /proc /0 gives mv: cannot move ‘/proc’ to ‘/0’: Device or resource busy
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74 views

How to find out the reason why ssh processes are hanging?

When I run command like iostat -dkx 2 2 via ssh, I get the expected result, but the processes on the local computer are saying alive in status "interruptible sleep". Why is this happening? Is there a ...
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1answer
60 views

Convert meminfo kB to bytes [duplicate]

To convert the readings in /proc/meminfo from "kB" to bytes, should I multiply by 1024, or 1000?
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1answer
55 views

Encoding of /proc/<pid>/cmdline files

I am thinking about working with the /proc/<pid>/cmdline files, but I couldn't find any documentation about the file encoding. The only piece of information I could find is located in the man ...
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2answers
192 views

Is there any way to hide kernel threads from ps command results?

When I type ps -ef , there are lots of special kernel thread processes showing. I am not interested in kernel threads; I am only interested in user process/thread. Is there a way that I can hide the ...
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2answers
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Recover from faking /proc/meminfo

So, without really thinking too much, I ran this script: #!/bin/bash SWAP="${1:-512}" NEW="$[SWAP*1024]"; TEMP="${NEW//?/ }"; OLD="${TEMP:1}0" sed "/^Swap\(Total\|Free\):/s,$OLD,$NEW," /proc/meminfo ...
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This name appears in multiple /proc/interrupts

The name of the interrupt appears as follows: Multiple.. (85:exynos4210-uart) root@test:~# cat /proc/interrupts CPU0 CPU1 CPU2 CPU3 28: 3543629726 1086578047 3268216812 ...
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836 views

How can I wake a process from sleep status via signal or /proc?

Many years ago I had an issue with Linux where processes would randomly go to sleep. Back then, I knew a trick with the /proc filesystem to trigger a wakeup of the process. I vaguely remember being ...
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fsync () get the impact of road /proc/sys/vm/drop_caches?

I have been testing the service life of TLC(1000write) SD card (4GB). SD card has been formatted with a fat partition. I am a write (), fsync () on a file of 10M SD card repeatedly. 1st (10M): ...
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247 views

cannot read key “net.ipv6.conf.all.stable_secret” in sysctl?

I am running kernel version as followings on an Arch Linux computer: [root@router ~ ]$ uname -a Linux router 4.2.5-1-ARCH #1 SMP PREEMPT Tue Oct 27 08:13:28 CET 2015 and I noticed that every time ...
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3answers
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How is the data in /proc/* gathered, and how reliable is it? [duplicate]

Recently I've been working with a cluster monitoring tool (ganglia) which aggregates system metrics from /proc/* on each machine. How is the data in /proc/* gathered? Who writes the data there? How ...
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1answer
295 views

What is the BOOT_IMAGE parameter in /proc/cmdline

I'm currently reading the book How Linux Works and in chapter 5 it talks about Linux parameters. Curious I started to see what were the parameters passed to my installed kernel when it boots up and ...
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225 views

(standard_in) illegal character when looping through a for loop

I'm trying to get statistics related to processes and general system information. If I do it without looping it runs fine, but if I put it within a loop it just gives me a chained error of illegal ...
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1answer
73 views

Does SSH access trigger keyboard interrupts?

So, I've been studying the basics for my LPIC-1, and I have a question about /proc/interrupts When consoled into a server, I can see key logging occurring (cat /proc/interrupts | grep i8042 count for ...
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Why number of dirty pages is always 0 on 2.6?

In /usr/src/linux/Documentation/filesystems/proc.txt i've found the string: Table 1-3: Contents of the statm files (as of 2.6.8-rc3) ...
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1answer
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Why is the size of “/proc/kcore” file so bigger than the physical memory size?

From proc manual: /proc/kcore This file represents the physical memory of the system and is stored in the ELF core file format. With this pseudo-file, and an unstripped kernel ...
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1answer
50 views

Best way to programatically detect the current host (by hardware features)

I have a hard drive with a Linux installation on it that I like to boot from different physical computers. My question is whether it's possible to programmatically detect which computer the drive is ...
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68 views

There is no /proc/bus/usb directory

I'm running a centos VM on ESXi. Does the /proc/bus/usb directory not show up until a USB device is connected? I just added a USB controller to the VM (it previously had non) and ran lsusb: $ ...
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1answer
77 views

What is /proc/dma? Is it just for legacy support?

I reading a Linux book that told me I can check the dma channels by reading /proc/dma. This is what I see when I run cat /proc/dma: 2: floppy 4: cascade I'm confused because that looks like old ...
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proc system interrupts information

There are many info under /proc For examples, for each process : raw format : cat /proc/< pid >/stat human readable : cat /proc/< pid >/status My goal is to read the info ...
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code generating /proc file system

In my assignment, I have added "casper" flag to task descriptor and it takes only 0, 1, 2 and 3 (default 0). I asked to "modify the code that generates the /proc filesystem so that its behavior is ...
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Under what circumstances, if any, will the result of reading /proc/cpuinfo change?

What I understand so far is that when a program opens and reads any file under /proc/, the kernel will generate the information on the fly. In the specific case of cpuinfo most of that data is ...
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1answer
43 views

What happened to /proc/sys/fs/relatime_interval?

According to one answer relatime interval can be changed by echo 60 > /proc/sys/fs/relatime_interval but I do not have such a file? Where did it go? $ ls /proc/sys/fs aio-max-nr ...
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1answer
155 views

iotop and ionice -p show a different class/priority for the same process

After running ionice -c2 -n7 <PID> on an I/O-intensive process (VirtualBox VM) and checking the result with ionice -p <PID> it shows best-effort: prio 7 which is expected. But when ...
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292 views

How to get UID and PID

So here's what I want to do: User inputs a USERNAME. Based on this username, I need to get the list of processes started by this user. I am planning to do this by getting the UID of this user and ...