A process is an instance of a computer program that is being executed.
76
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11answers
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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.
43
votes
6answers
10k 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 ...
38
votes
3answers
16k 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 ...
34
votes
6answers
10k views
How can I disown a running process and associate it to a new screen shell?
I have a running program on a SSH shell. I want to pause it and be able to unpause its execution when I come back.
One way I thought of doing that was to transfer its ownership to a screen shell, ...
29
votes
4answers
13k 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 ...
23
votes
2answers
2k views
Why is the default process creation mechanism fork?
The UNIX system call for process creation, fork(), creates a child process by copying the parent process. My understanding is that this is almost always followed by a call to exec() to replace the ...
21
votes
4answers
1k 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
368 views
When you try to terminate a process for good, which option for “kill” should you use?
I am getting a lot of mixed messages from people, and was wondering if it there really is not much of a difference in what you use.
kill 'x'
killall 'x'
kill -9 'x'
These are some options I've been ...
19
votes
3answers
30k views
How can I get a full process list in solaris, without truncated lines?
Is there a way to generate a full process listing in solaris, without truncated lines? I've tried the ps commmand, with the following arguments:
-f Generates a full listing. ...
18
votes
4answers
737 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?
18
votes
3answers
706 views
Can other users view the arguments passed to a command?
If I invoke a command with arguments like so:
bob@bob-pc:~$ command -arg1 -arg2
...can other users view the arguments passed to the command?
18
votes
3answers
4k views
What are “session leaders” in `ps`?
What are session leaders, as in ps -d which selects all processes except session leaders?
18
votes
5answers
13k views
How to find which processes are taking all the memory?
I'm looking for somthing like top is to CPU usage. Is there a command line argument for top that does this? Currently, my memory is so full that even 'man top' fails with out of memory :)
17
votes
4answers
4k views
Determine which process is creating a file
Given file path, how can I determine which process creates it (and/or reads/writes to it)?
16
votes
4answers
2k 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. ...
16
votes
1answer
493 views
How does systemd survive a kill -9?
Between the recent "Why does 'kill -9 0' end my console session" and "How to get a kernel panic" questions, I got a bur under my saddle and tried kill -9 1 on a mostly up-to-date Arch linux laptop. I ...
16
votes
2answers
3k views
Who's got the other end of this unix socketpair?
I want to determine what process has the other end of a unix socket, that was created with socketpair().
I have a program parent which creates a socketpair(AF_UNIX, SOCK_STREAM, 0, fds), and fork()s. ...
15
votes
2answers
2k views
What is the difference between a job and a process?
What is the difference between a "job" and a "process"?
15
votes
4answers
10k 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.
15
votes
4answers
2k 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 ...
14
votes
4answers
2k views
How do I find out which processes are preventing unmounting of a device?
Sometimes, I would like to umount a usb device, but I get a drive is busy error.
How do I find out which processes or programs are accessing the device?
14
votes
2answers
445 views
How are the processes in UNIX numbered?
I can't find any pattern when I look at the numbering of PIDs in process table (ps -a), as the PIDs are not subsequent numbers and sometimes there are large "gaps" between those numbers.
Is it ...
13
votes
3answers
961 views
How to kill a process with a single command?
I want to kill a process, after finding the id in a single step.
I currently use these two commands:
pidof <name>
kill <#number_which_is_result_of_command>
How can I write a single ...
13
votes
5answers
4k 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 ...
13
votes
3answers
15k 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.
13
votes
3answers
441 views
Limiting a specific shell's internet bandwidth usage
I want update my linux in one shell but by default wget or axel in updater use all the bandwidth.
How can I limit the speed in this shell?
I want other shells to have a fair share, and to limit ...
13
votes
3answers
1k 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?
12
votes
4answers
491 views
Is there a program that can send me a notification e-mail when a process finishes?
I am a computational scientist, and I run a lot of lengthy calculations on Linux. Specifically, I run molecular dynamics (MD) simulations using the GROMACS package. These simulations can take days ...
12
votes
5answers
3k views
Is there a way to limit the amount of memory a particular process can use in Unix?
I need to test a process for memory management.
I do not have the source, so I need to do all the testing from the OS side.
I want to be able to say something like limitmemory 400k -p <pid>
...
12
votes
2answers
270 views
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 ...
11
votes
5answers
2k views
What is using this network socket?
I'm trying to use NTP to update the time on my machine. However, it gives me an error:
host # ntpdate ntp1.example.org
10 Aug 12:38:50 ntpdate[7696]: the NTP socket is in use, exiting
What does the ...
11
votes
3answers
3k views
What would cause ps to report uid instead of username?
I have Eucalyptus installed on my Linux machine, and I've noticed that for processes owned by the eucalyptus user, ps reports the userid instead of the username. For example:
$ sudo -i -u eucalyptus
...
11
votes
1answer
2k views
How to tell if a running program is 64-bit in Linux?
In Mac OS X, I could use the Activity Monitor program to see if a running program/process is 64-bit. How do I do that in a Linux OS, regardless of flavour? Thanks.
11
votes
2answers
884 views
Is there a way to intercept interprocess communication in Unix/Linux?
For intercepting/analyzing network traffic, we have a utility called Wireshark.
Do we have a similar utility for intercepting all the interprocess communication between any two processes in ...
11
votes
4answers
356 views
How can I find which process sends data to a specific port?
I have a service, keeping a certain port open.
I'm getting data to it, that I neither expect nor want to get, and I'm trying to pin-point the source of this data. So how can I find which process that ...
11
votes
4answers
283 views
Is there a top-like command that shows the network bandwidths and file accesses of running processes
For example, we'd like to see:
PROCESS IF TX RX FILE(regular) R/W
prog1 eth0 200kB/s 12kB/s -- --
wlan0 12kB/s 100kB/s -- ...
10
votes
4answers
537 views
What is the difference between running a executable just by name and by appending a dot /slash before it?
This is the output from ls -all command :
-rwxr----- 1 subhrcho dba 3600 Nov 13 17:26 jdev
-rw-r----- 1 subhrcho dba 1566 Nov 13 17:26 jdev-Darwin.conf
-rw-r----- 1 subhrcho dba 347 Mar 6 2009 ...
10
votes
2answers
2k views
After fork(), where does the child begin its execution?
I'm trying to learn UNIX programming and came across a question regarding fork(). I understand that fork() creates an identical process of the currently running process, but where does it start? For ...
10
votes
3answers
8k 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 ...
10
votes
2answers
4k 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 ...
10
votes
2answers
382 views
Why does bash show 'Terminated' after killing a process?
Here is the behaviour I want to understand:
$ ps
PID TTY TIME CMD
392 ttys000 0:00.20 -bash
4268 ttys000 0:00.00 xargs
$ kill 4268
$ ps
PID TTY TIME CMD
392 ttys000 ...
10
votes
3answers
2k views
Can I limit a process to a certain amount of time / CPU cycles?
We have a script which runs on our web servers, triggered by customer action, which initiates a unix process to generate some cache files. Because this process acts upon files supplied by our ...
10
votes
4answers
13k views
Is there a way to see details of all the threads that a process has in Linux?
For Windows, I think Process Explorer shows you all the threads under a process.
Is there a similar command line utility for Linux that can show me details about all the threads a particular process ...
10
votes
3answers
6k views
Where can I see a list of kernel killed processes?
Is there some way I can check which of my processes the kernel has killed? Sometimes I log onto my server and find that something that should've run all night just stopped 8 hours in and I'm unsure if ...
10
votes
1answer
978 views
per process swapiness for linux
/proc/sys/vm/swappiness is nice but i want a knob that's per process like /proc/$PID/oom_adj so that i can make certain processes less likely than others to have any of their pages swapped out unlike ...
10
votes
2answers
480 views
Is there an upper limit to the number of zombie processes you can have?
I used to work with an HP-UX system and the old admin told me there is an upper limit on the number of zombie processes you can have on the system, I believe 1024.
Is this a hard fact ceiling? I ...
10
votes
4answers
353 views
In bash, what are potential negative consequences of pausing a process with control-z?
Using bash, one can pause a process with control-z. However, are there any general circumstances or guidelines to beware of where a process would not behave well with being paused?
My specific ...
10
votes
2answers
2k 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 | ...
10
votes
3answers
346 views
Maintain 100 instances of a program running
I'm currently using supervisord to maintain 100 instances of a script running at once. If any die then it starts up a new one.
However it seems to be struggling maintaining larger numbers (>300 ...
9
votes
1answer
240 views
How do I monitor opened files of a process in realtime?
I know I can view the open files of a process using lsof at that moment in time on my Linux machine. However, a process can open, alter and close a file so quickly that I won't be able to see it when ...
