Hi I need to restart a running C process from Linux prompt. I googled it and some sites suggested SIGHUP which is not working in my case. Any other suggestions/pointers?
I have following code snippet
#include <stdio.h>
#include <unistd.h>
int main() {
fprintf(stderr,"%s","Entering main function\n");
while(1) {
sleep (1);
}
fprintf(stderr,"%s","Exiting main function\n");
return;
}
Linux output
#] ./simple &
[1] 489440
#] Entering main function
#] ps aux | grep simple
user 489440 0.0 0.0 3924 360 pts/135 S 13:25 0:00 ./simple
user 489710 0.0 0.0 105312 804 pts/135 S+ 13:25 0:00 grep simple
#] kill -1 489440
[1] Hangup ./simple
#] ps aux | grep simple
user 490181 0.0 0.0 105312 800 pts/135 S+ 13:25 0:00 grep simple
#]
If you want to use signals to re-start your process, you can in theory create your own signal handler for SIGHUP and and have the signal handler exec your program+arguments again. Although; I suspect you may want to really read up on signal handlers and the semantics around them before undertaking this.
See: man signal and man execvp
Restart a process is to stop it and start it again. So you may just kill the process and start it again. Also, you may easily write a script to kill and start a process (by its name or by its pid).
Related
Trying to stop Apache2 service, but get PID error:
#service apache2 stop
[FAIL] Stopping web server: apache2 failed!
[....] There are processes named 'apache2' running which do not match your pid file which are left untouched in the name of safety, Plea[warnview the situation by hand. ... (warning).
Trying to kill, those processes:
#kill -9 $(ps aux | grep apache2 | awk '{print $2}')
but they get re-spawned again:
#ps aux | grep apache2
root 19279 0.0 0.0 4080 348 ? Ss 05:10 0:00 runsv apache2
root 19280 0.0 0.0 4316 648 ? S 05:10 0:00 /bin/sh /usr/sbin/apache2ctl -D FOREGROUND
root 19282 0.0 0.0 91344 5424 ? S 05:10 0:00 /usr/sbin/apache2 -D FOREGROUND
www-data 19284 0.0 0.0 380500 2812 ? Sl 05:10 0:00 /usr/sbin/apache2 -D FOREGROUND
www-data 19285 0.0 0.0 380500 2812 ? Sl 05:10 0:00 /usr/sbin/apache2 -D FOREGROUND
And though the processes are running i can't connect to the server on port 80. /var/log/apache2/error.log.1 has no new messages when i do the kill -9.
Before I tried to restart everything worked perfectly.
Running on Debian: Linux adara 3.2.0-4-amd64 #1 SMP Debian 3.2.54-2 x86_64 GNU/Linux
UPD:
also tried apache2ctl:
#/usr/sbin/apache2ctl -k stop
AH00526: Syntax error on line 76 of /etc/apache2/apache2.conf:
PidFile takes one argument, A file for logging the server process ID
Action '-k stop' failed.
The Apache error log may have more information.
but there is no pid file in /var/run/apache2
I'm new to linux, looks like it has to do something with startup scripts, but can't figure out what exactly.
Below is the command to find out the process running on port 80
lsof -i tcp:80
Kill the process with PID.Restart the system once to check if their is any start up script executing and using the Port 80 which is preventing you to start your service.
For start up scripts you can check
/etc/init.d/ or /etc/rc.local or crontab - e
You can try Apache official documentation for stop/restart operations.
link
I'm new to linux.
How can I show a list of all processes that says about each process if it's running or suspended?
I've tried
ps -ef|grep myusername
but it doesn't say if the processes are running or not.
also tried
ps ux
same thing, it doesn't say if the processes are running or not.
I'm looking for something like this list:
I get this list when I move a process to background, I don't know how to see it otherwise...
You can use "ps" to list processes, This (ps aux) will list all the processes. Given an example output of it below.
ps aux | more
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.0 0.1 189160 9376 ? Ss 15:51 0:04 /usr/lib/systemd/systemd --switched-root --system --deserialize 20
root 2 0.0 0.0 0 0 ? S 15:51 0:00 [kthreadd]
root 3 0.0 0.0 0 0 ? S 15:51 0:00 [ksoftirqd/0]
root 5 0.0 0.0 0 0 ? S< 15:51 0:00 [kworker/0:0H]
root 7 0.0 0.0 0 0 ? S 15:51 0:06 [rcu_sched]
root 8 0.0 0.0 0 0 ? S 15:51 0:00 [rcu_bh]
root 9 0.0 0.0 0 0 ? S 15:51 0:04 [rcuos/0]
By checking the STAT of the process ( UNDER "STAT" ) you can identify the process states, Below are some possible states codes.
R running or runnable (on run queue)
D uninterruptible sleep (usually IO)
S interruptible sleep (waiting for an event to complete)
Z defunct/zombie, terminated but not reaped by its parent
T stopped, either by a job control signal or because it is being
traced
You can type "man ps" to get more info.
You can use htop to see the list of processes and there is a column for process state
What does a C process status mean in htop?
http://www.howtogeek.com/howto/ubuntu/using-htop-to-monitor-system-processes-on-linux/
ps -p PID -o comm=
Enter the code above where PID is PID of the process.
Following command will be more helpful to you.
Use the command : sudo lsof -i -n -P
This command lists the Application Name, PID, User, IP version, Device ID and the Node with Port Name. It shows both TCP and UDP.
Variations :
To format it in a nice, readable way; use :
sudo lsof -i -n -P | more
To view view only TCP connections :
sudo lsof -i -n -P | grep TCP | more
To view view only UDP connections :
sudo lsof -i -n -P | grep UDP | more
I know if I type ps -ef I get the processes. But how can I read the process tree of a user say xyz, so that I can draw it in hierarchal form?
Should I read the file path towards process and draw it as a tree structure? Or what?
Here is a selection from a larger ps -ef output:
UID PID PPID C STIME TTY TIME CMD
....
xyz 15152 15112 0 23:08:00 pts/19 0:00 usr/bin/bash
xyz 15112 15106 0 23:07:54 ? 0:00 /local/openssh/4.5p1/sbin/sshd -R
root 236 6535 0 21:27:06 ? 0:01 /local/openssh/4.5p1/sbin/sshd -R
xyz 15431 15152 0 23:09:30 pts/19 0:00 ps -ef
.....
How can I draw the process hierarchy of xyz?
Thanks
pstree [options] [pid or username];
see http://www.linfo.org/pstree.html and http://manpages.ubuntu.com/manpages/precise/man1/pstree.1.html
You can use htop -u USERNAME and then press F5
I am looking for a general method to launch and then kill an R process, including possibly all forks or other processes that it invoked.
For example, a user runs a script like this:
library(multicore);
for(i in 1:3) parallel(foo <- "bar");
for(i in 1:3) system("sleep 300", wait=FALSE);
for(i in 1:3) system("sleep 300&");
q("no")
After the user quits the R session, the child processes are still running:
jeroen#jeroen-ubuntu:~$ ps -ef | grep R
jeroen 4469 1 0 16:38 pts/1 00:00:00 /usr/lib/R/bin/exec/R
jeroen 4470 1 0 16:38 pts/1 00:00:00 /usr/lib/R/bin/exec/R
jeroen 4471 1 0 16:38 pts/1 00:00:00 /usr/lib/R/bin/exec/R
jeroen 4502 4195 0 16:39 pts/1 00:00:00 grep --color=auto R
jeroen#jeroen-ubuntu:~$ ps -ef | grep "sleep"
jeroen 4473 1 0 16:38 pts/1 00:00:00 sleep 300
jeroen 4475 1 0 16:38 pts/1 00:00:00 sleep 300
jeroen 4477 1 0 16:38 pts/1 00:00:00 sleep 300
jeroen 4479 1 0 16:38 pts/1 00:00:00 sleep 300
jeroen 4481 1 0 16:38 pts/1 00:00:00 sleep 300
jeroen 4483 1 0 16:38 pts/1 00:00:00 sleep 300
jeroen 4504 4195 0 16:39 pts/1 00:00:00 grep --color=auto sleep
To make things worse, their their parent process id is 1 making it hard to identify them. Is there a method to run an R script in a way that allows me to recursively kill the process and its children at any time?
Edit: so I don't want to manually have to go in to search & kill processes. Also I don't want to kill all R processes, as there might be others that are doing fine. I need a method to kill a specific process and all of its children.
This is mainly about the multicore part. Children are waiting for you to collect the results - see ?collect. Normally, you should never use parallel without a provision to clean up, typically in on.exit. multicore cleans up in high-level functions like mclapply, but if you use lower-level functions it is your responsibility to perform the cleanup (since multicore cannot know if you left the children running intentionally or not).
Your example is really bogus, because you don't even consider collecting results. But anyway, if that is really what you want, you'll have to do the cleanup at some point. For example, if you want to terminate all children on exit, you could define .Last like this:
.Last <- function(...) {
collect(wait=FALSE)
all <- children()
if (length(all)) {
kill(all, SIGTERM)
collect(all)
}
}
Again, the above is not a recommended way to deal with this - it rather a last resort. You should really assign jobs and collect results like
jobs <- lapply(1:3, function(i) parallel({Sys.sleep(i); i}))
collect(jobs)
As for the general process child question - init inherits the children only after R quits, but in .Last you can still find their pids since the parent process exists at that point so you could perform similar cleanup as in the multicore case.
Before the user quits the R session, the processes you want to kill will have parent process ID equal to the process ID of the session that started them. You could perhaps use the .Last or .Last.sys hooks (see help(q)) to kill all processes with the appropriate PPID at that point; those can be suppressed with q(runLast=FALSE), so it isn't perfect, but I think it's the best option you have.
After the user quits the R session, there is no reliable way to do what you want -- the only record the kernel keeps of process parentage is the PPID you see in ps -ef, and when a parent process exits, that information is destroyed, as you have discovered.
Note that if one of the child processes forks, the grandchild will have PPID equal to the child's PID, and that will get reset to 1 when the child exits, which it might do before the grandparent exits. Thus, there is no reliable way to catch all of a process's descendants in general, even if you do so before the process exits. (One hears that "cgroups" provide a way, but one is unfamiliar with the details; in any case, that is an optional feature which only some iterations/configurations of the Linux kernel provide, and is not available at all elsewhere.)
I believe the latter part of the question is more a consideration of the shell, rather than the kernel. (Simon Urbanek has answered the multicore part better than pretty much anyone else could, as he's the author. :))
If you're using bash, you can find the PID of the most recently launched child process in $!. You can aggregate the PIDs and then be sure to kill those off when you close R.
If you want to be really gonzo, you could store parent PID (i.e. the output of Sys.getpid()) and child PID in a file and have a cleaning daemon that checks whether or not the parent PID exists and, if not, kills the orphans. I don't think it'll be that easy to get a package called oRphanKilleR onto CRAN, though.
Here is an example of appending the child PID to a file:
system('(sleep 20) & echo $! >> ~/childPIDs.txt', wait = FALSE)
You can modify this to create your own shell command and use R's tempfile() command to create a temporary file (albeit, that will disappear when the R instance is terminated, unless you take a special effort to preserve the file via permissions).
For some other clever ideas, see this other post on SO.
You can also create a do while loop in the shell that will check for whether or not a particular PID is in existence. While it is, the loop sleeps. Once the loop terminates (because the PID is no longer in use), the script will kill another PID.
Basically, I think your solution will be in shell scripting, rather than R.
I'm writing a plugin to highlight text strings automatically as you visit a web site. It's like the highlight search results but automatic and for many words; it could be used for people with allergies to make words really stand out, for example, when they browse a food site.
But I have problem. When I try to close an empty, fresh FF window, it somehow blocks the whole process. When I kill the process, all the windows vanish, but the Firefox process stays alive (parent PID is 1, doesn't listen to any signals, has lots of resources open, still eats CPU, but won't budge).
So two questions:
How is it even possible for a process not to listen to kill -9 (neither as user nor as root)?
Is there anything I can do but a reboot?
[EDIT] This is the offending process:
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
digulla 16688 4.3 4.2 784476 345464 pts/14 D Mar28 75:02 /opt/firefox-3.0/firefox-bin
Same with ps -ef | grep firefox
UID PID PPID C STIME TTY TIME CMD
digulla 16688 1 4 Mar28 pts/14 01:15:02 /opt/firefox-3.0/firefox-bin
It's the only process left. As you can see, it's not a zombie, it's running! It doesn't listen to kill -9, no matter if I kill by PID or name! If I try to connect with strace, then the strace also hangs and can't be killed. There is no output, either. My guess is that FF hangs in some kernel routine but which?
[EDIT2] Based on feedback by sigjuice:
ps axopid,comm,wchan
can show you in which kernel routine a process hangs. In my case, the offending plugin was the Beagle Indexer (openSUSE 11.1). After disabling the plugin, FF was a quick and happy fox again.
As noted in comments to the OP, a process status (STAT) of D indicates that the process is in an "uninterruptible sleep" state. In real-world terms, this generally means that it's waiting on I/O and can't/won't do anything - including dying - until that I/O operation completes.
Processes in a D state will normally only be there for a fraction of a second before the operation completes and they return to R/S. In my experience, if a process gets stuck in D, it's most often trying to communicate with an unreachable NFS or other remote filesystem, trying to access a failing hard drive, or making use of some piece of hardware by way of a flaky device driver. In such cases, the only way to recover and allow the process to die is to either get the fs/drive/hardware back up and running so the I/O can complete or to give up and reboot the system. In the specific case of NFS, the mount may also eventually time out and return from the I/O operation (with a failure code), but this is dependent on the mount options and it's very common for NFS mounts to be set to wait forever.
This is distinct from a zombie process, which will have a status of Z.
Double-check that the parent-id is really 1. If not, and this is firefox, first try sudo killall -9 firefox-bin. After that, try killing the specific process IDs individually with sudo killall -9 [process-id].
How is it even possible for a process not to listen to kill -9 (neiter as user nor as root)?
If a process has gone <defunct> and then becomes a zombie with a parent of 1, you can't kill it manually; only init can. Zombie processes are already dead and gone - they've lost the ability to be killed as they are no longer processes, only a process table entry and its associated exit code, waiting to be collected. You need to kill the parent, and you can't kill init for obvious reasons.
But see here for more general information. A reboot will kill everything, naturally.
Is it possible, that this process is restarted (for example by init) just at the time you kill it?
You can check this easily. If the PID is the same after kill -9 PID then the process wasn't killed, but if it has changed the process has been restarted.
I lately get trapped into a pitfall of Double Fork and had landed to this page before finally finding my answer. The symptoms are identical even if the problem is not the same:
WYKINWYT :What You Kill Is Not What You Thought
The minimal test code is shown below based on an example for an SNMP Daemon
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
int main(int argc, char* argv[])
{
//We omit the -f option (do not Fork) to reproduce the problem
char * options[]={"/usr/local/sbin/snmpd",/*"-f","*/-d","--master=agentx", "-Dagentx","--agentXSocket=tcp:localhost:1706", "udp:10161", (char*) NULL};
pid_t pid = fork();
if ( 0 > pid ) return -1;
switch(pid)
{
case 0:
{ //Child launches SNMP daemon
execv(options[0],options);
exit(-2);
break;
}
default:
{
sleep(10); //Simulate "long" activity
kill(pid,SIGTERM);//kill what should be child,
//i.e the SNMP daemon I assume
printf("Signal sent to %d\n",pid);
sleep(10); //Simulate "long" operation before closing
waitpid(pid);
printf("SNMP should be now down\n");
getchar();//Blocking (for observation only)
break;
}
}
printf("Bye!\n");
}
During the first phase the main process (7699) launches the SNMP daemon (7700) but we can see that this one is now Defunct/Zombie. Beside we can see another process (7702) with the options we specified
[nils#localhost ~]$ ps -ef | tail
root 7439 2 0 23:00 ? 00:00:00 [kworker/1:0]
root 7494 2 0 23:03 ? 00:00:00 [kworker/0:1]
root 7544 2 0 23:08 ? 00:00:00 [kworker/0:2]
root 7605 2 0 23:10 ? 00:00:00 [kworker/1:2]
root 7698 729 0 23:11 ? 00:00:00 sleep 60
nils 7699 2832 0 23:11 pts/0 00:00:00 ./main
nils 7700 7699 0 23:11 pts/0 00:00:00 [snmpd] <defunct>
nils 7702 1 0 23:11 ? 00:00:00 /usr/local/sbin/snmpd -Lo -d --master=agentx -Dagentx --agentXSocket=tcp:localhost:1706 udp:10161
nils 7727 3706 0 23:11 pts/1 00:00:00 ps -ef
nils 7728 3706 0 23:11 pts/1 00:00:00 tail
After the 10 sec simulated we will try to kill the only process we know (7700). What we succeed at last with waitpid(). But Process 7702 is still here
[nils#localhost ~]$ ps -ef | tail
root 7431 2 0 23:00 ? 00:00:00 [kworker/u256:1]
root 7439 2 0 23:00 ? 00:00:00 [kworker/1:0]
root 7494 2 0 23:03 ? 00:00:00 [kworker/0:1]
root 7544 2 0 23:08 ? 00:00:00 [kworker/0:2]
root 7605 2 0 23:10 ? 00:00:00 [kworker/1:2]
root 7698 729 0 23:11 ? 00:00:00 sleep 60
nils 7699 2832 0 23:11 pts/0 00:00:00 ./main
nils 7702 1 0 23:11 ? 00:00:00 /usr/local/sbin/snmpd -Lo -d --master=agentx -Dagentx --agentXSocket=tcp:localhost:1706 udp:10161
nils 7751 3706 0 23:12 pts/1 00:00:00 ps -ef
nils 7752 3706 0 23:12 pts/1 00:00:00 tail
After giving a character to the getchar() function our main process terminates but the SNMP daemon with the pid 7002 is still here
[nils#localhost ~]$ ps -ef | tail
postfix 7399 1511 0 22:58 ? 00:00:00 pickup -l -t unix -u
root 7431 2 0 23:00 ? 00:00:00 [kworker/u256:1]
root 7439 2 0 23:00 ? 00:00:00 [kworker/1:0]
root 7494 2 0 23:03 ? 00:00:00 [kworker/0:1]
root 7544 2 0 23:08 ? 00:00:00 [kworker/0:2]
root 7605 2 0 23:10 ? 00:00:00 [kworker/1:2]
root 7698 729 0 23:11 ? 00:00:00 sleep 60
nils 7702 1 0 23:11 ? 00:00:00 /usr/local/sbin/snmpd -Lo -d --master=agentx -Dagentx --agentXSocket=tcp:localhost:1706 udp:10161
nils 7765 3706 0 23:12 pts/1 00:00:00 ps -ef
nils 7766 3706 0 23:12 pts/1 00:00:00 tail
Conclusion
The fact that we ignored the double fork mechanism made us think that the kill action did not succeed. But in fact we simply killed the wrong process !!
By adding the -f option ( Do Not (Double) Fork ) all go as expected
ps -ef | grep firefox;
and you can see 3 process, kill them all.
sudo killall -9 firefox
Should work
EDIT: [PID] changed to firefox
You can also do a pstree and kill the parent. This makes sure that you get the entire offending process tree and not just the leaf.