A process is an instance of a computer program that is being executed.

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123
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7answers
75k views

Keep SSH Sessions running after disconnection

I sometimes have long running processes that I want to kick off before going home, so I create a SSH session to the server to start the process, but then I want to close my laptop and go home and ...
262
votes
12answers
243k views

What if 'kill -9' does not work?

I have a process I can't kill with kill -9 <pid>. What's the problem in such a case, especially since I am the owner of that process. I thought nothing could evade that kill option.
94
votes
4answers
63k views

How do I read from /proc/$pid/mem under Linux?

The Linux proc(5) man page tells me that /proc/$pid/mem “can be used to access the pages of a process's memory”. But a straightforward attempt to use it only gives me $ cat /proc/$$/mem /proc/self/...
143
votes
11answers
128k views

How can I close a terminal without killing the command running in it?

Sometimes I want to start a process and forget about it. If I start it from the command line, like this: redshift I can't close the terminal, or it will kill the process. Can I run a command in ...
40
votes
5answers
40k views

How to determine which process is creating a file? [duplicate]

Given file path, how can I determine which process creates it (and/or reads/writes to it)?
38
votes
5answers
10k views

What process created this X11 window?

Given an X11 window ID, is there a way to find the ID of the process that created it? Of course this isn't always possible, for example if the window came over a TCP connection. For that case I'd ...
37
votes
8answers
13k views

Block network access of a process?

Is it possible to block the (outgoing) network access of a single process?
37
votes
2answers
16k views

What do the brackets around processes mean?

mark@mark-VirtualBox:~/auto/lib$ ps -Awwo pid,comm,args PID COMMAND COMMAND 1 init /sbin/init 2 kthreadd [kthreadd] 3 ksoftirqd/0 [ksoftirqd/0] 5 ...
7
votes
2answers
2k 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, ...
31
votes
4answers
7k views

What's the difference between running a program as a daemon and forking it into background with '&'?

What are the practical differences from a sysadmin point of view when deploying services on a unix based system?
38
votes
5answers
15k views

Measuring RAM usage of a program

time is a brilliant command if you want to figure out how much CPU time a given command takes. I am looking for something similar that can measure the max RAM usage of the program and any children. ...
3
votes
2answers
647 views

Is there a log of past threads that are now closed?

Sometimes, I have a rogue Java process which takes up 100% of my CPU and makes it jump about 30C in temperature (usually resulting in a crash if not killed). Problem is, I can never really identify ...
30
votes
6answers
10k views

Who's got the other end of this unix socketpair?

I want to determine which process has the other end of a UNIX socket. Specifically, I'm asking about one that was created with socketpair(), though the problem is the same for any UNIX socket. I ...
105
votes
4answers
100k views

How to get the pid of the last executed command in shell script?

I want to have a shell script like this: my-app & echo $my-app-pid But I do not know how the get the pid of the just executed command. I know I can just use the jobs -p my-app command to grep ...
10
votes
1answer
1k views

Reliable way to jail child processes using `nsenter:`

I know that Linux namespaces, among many other things, can be leveraged to handle restricting and jailing child processes securely without any chance of their being zombied and dumped on init. But I'm ...
25
votes
3answers
3k views

How can I set the processor affinity of a process on Linux?

The question is all in the title: How can I set the processor affinity of a process on Linux?
6
votes
2answers
2k views

Hide processes from other users based on groups (under Linux)?

Is it possible to configure process hiding for certain user groups under a linux system? For example: Users from group X should not see processes owned by users from group Y in ps/top or under /proc. ...
112
votes
5answers
130k views

How to check how long a process has been running?

I would like to avoid doing this by launching the process from a monitoring app.
8
votes
4answers
4k views

New parent process when the parent process dies

In UNIX, when a parent process disappears, I thought that all child processes reset init as their parent. Is this not correct all the time? Are there any exceptions?
7
votes
4answers
22k views

Finding the ID of a process and killing it

When ever I need to kill a background process I do ps -e | grep <process_name> Which prints something like this 1766 ? 00:00:13 conky , Then I use the process ID to kill it like so kill 1766 . ...
44
votes
3answers
77k views

Find and remove large files that are open but have been deleted

How does one find large files that have been deleted but are still open in an application? How can one remove such a file, even though a process has it open? The situation is that we are running a ...
24
votes
1answer
13k views

What is the maximum value of the PID of a process?

What is the maximum value of the PID of a process? Also, is it possible to change the PID of a running process?
10
votes
1answer
2k views

Turning off swapping for only one process with cgroups?

I would like to turn off swapping for only one process. Swap should work as usual for the other processes. How I can implement this with cgroups?
4
votes
4answers
20k views

Check for Process if Same is Running

Is there a script or a way in linux that when I try to execute a shell script/process, if the same is running, it will prompt that same is running and will exit otherwise it will continue.
50
votes
5answers
8k views

How can I check what signals a process is listening to?

How can I verify whether a running process will catch a signal, or ignore it, or block it? Ideally I'd like to see a list of signals, or at least not have to actually send the signal to check.
19
votes
5answers
19k views

view stdout for another pts [duplicate]

Here is the situation. I left my pc at home doing an rsync from a 2TB hard drive to another 2TB hard drive (it's going to take a while since they are both USB 2.0). I am now at work and I have ssh-ed ...
32
votes
9answers
5k views

How can I kill a process and be sure the PID hasn't been reused

Suppose, for example, you have a shell script similar to: longrunningthing & p=$! echo Killing longrunningthing on PID $p in 24 hours sleep 86400 echo Time up! kill $p Should do the trick, ...
20
votes
4answers
6k views

What happens to the output of a process that has been disowned and lost its terminal?

If I close the virtual terminal, where some process was started, does the output just go straight to /dev/null, or can it pollute memory somehow? Can I anyhow grab the output to continue reading it at ...
20
votes
3answers
19k views

How to read environment variables of a process

Linux's /proc/<pid>/environ does not update (as I understand it, the file contain the initial environment of the process). How can I read a process's current environment?
3
votes
1answer
3k views

per process private file system mount points

I was checking unshare command and according to it's man page, unshare - run program with some namespaces unshared from parent I also see there is a type of namespace listed as, mount ...
40
votes
5answers
51k views

How to view the output of a running process in another bash session?

I have left a script running on a remote machine from when I was locally working at it. I can connect over SSH to the machine as the same user and see the script running in ps. $ ps aux | grep ...
84
votes
4answers
2k views

Can I somehow add a “&& prog2” to an already running prog1?

Most shells provide functions like && and ; to chain the execution of commands in certain ways. But what if a command is already running, can I still somehow add another command to be executed ...
43
votes
3answers
18k views

What are “session leaders” in `ps`?

What are session leaders, as in ps -d which selects all processes except session leaders?
59
votes
6answers
99k views

How to monitor CPU/memory usage of a single process?

I would like to monitor one process's memory / cpu usage in real time. Similar to top but targeted at only one process, preferably with a history graph of some sort.
39
votes
2answers
38k views

Limit process to one cpu core

How to limit process to one cpu core ? Something similar to ulimit or cpulimit would be nice. (Just to ensure: I do NOT want to limit percentage usage or time of execution. I want to force app (with ...
57
votes
3answers
32k views

Find out current working directory of a running process?

What command(s) can one use to find out the current working directory (CWD) of a running process? These would be commands you could use externally from the process.
61
votes
2answers
21k views

Why does `htop` show more process than `ps`

In ps xf 26395 pts/78 Ss 0:00 \_ bash 27016 pts/78 Sl+ 0:04 | \_ unicorn_rails master -c config/unicorn.rb 27042 pts/78 Sl+ 0:00 | ...
35
votes
4answers
5k views

Is there any UNIX variant on which a child process dies with its parent?

I have been studying the Linux kernel behaviour for quite some time now, and it's always been clear to me that: When a process dies, all its children are given back to the init process (PID 1) ...
32
votes
4answers
34k views

How can I pause/resume rsync

How can I pause an rsync that's running? First time I did Ctrl+C to kill it and used the -P flag to run again. Is this prone to corrupt the current file transfer? Second time I simply put MacOS to ...
34
votes
4answers
8k views

Save entire process for continuation after reboot

I developed an algorithm for a fairly hard problem in mathematics which is likely to need several months to finish. As I have limited resources only, I started this on my Ubuntu 12.04 (x86) laptop. ...
19
votes
2answers
5k views

Why does process substitution result in a file called /dev/fd/63 which is a pipe?

I am trying to understand named pipes in the context of this particular example. I type <(ls -l) in my terminal and get the output as, bash: /dev/fd/63: Permission denied. If I type cat <(ls -...
22
votes
6answers
15k views

How can I close a terminal without killing its children (without running `screen` first)?

sometimes I run an app in the gnome-terminal, but then I suddenly have to restart gnome or something. I guess the answer to the question is also useful then I want to disconnect from SSH where ...
28
votes
3answers
14k views

What is the difference between a job and a process?

What is the difference between a "job" and a "process"?
6
votes
2answers
5k views

Write inside a socket open by another process in Linux

Is it possible on Linux for a process to write inside a socket open by another one? Let's say I open a connection to google.com using netcat: myuser@linux:~$ nc google.com 80 Now I can lookup for ...
13
votes
5answers
14k views

How to send keystrokes (F5) from terminal to a process?

I'm using an Raspberry Pi in combination with Chromium (kiosk mode) to show up some stats. The Pi doesn't have an connected keyboard so I searched for a solution to send keystrokes from the terminal ...
4
votes
1answer
284 views

Shared library mappings in /proc/pid/maps

Why does /proc/pid/maps contain a few records for the same library ? Here is an example: 7fae7db9f000-7fae7dc8f000 r-xp 00000000 08:05 536861 /usr/lib/x86_64-linux-gnu/libstdc++....
6
votes
3answers
913 views

Understanding environmental variables in different contexts

Trying to understand the behaviour of the environment in Linux (Ubuntu 13.04 concretely), I've find different situations where setting envirionment variables are used or defined for/in different ...
5
votes
1answer
2k views

I don't want other users see my processes in ps aux. I have root. It's Debian. How to use grsec?

I installed 'linux-patch-grsecurity2' and it has some sort of interface. ~$ sudo gradm2 gradm 2.1.14 grsecurity administration program Usage: gradm [option] ... Examples: gradm -P ...
10
votes
5answers
4k views

Process descendants

I'm trying to build a process container. The container will trigger other programs. For example - a bash script that launches running background tasks with '&' usage. The important feature I'm ...
8
votes
5answers
4k views

Understanding top and load average

I'm observing a high load average on a certain machine (about 9) in all three load fields. I understand load as the number of processes in state "run" / currently desiring CPU time. Am I correct at ...