I have simple batch script in linux debian - Debian GNU/Linux 6.0 - that stop process then deletes log files and start the process again :
#!/bin/bash
killall -KILL rsyslogd
sleep 5s
rm /var/log/syslog
rm /var/log/messages
rm /var/log/kern.log
sleep 3s
rsyslogd
exit
The process name is rsyslogd. I have to close it before deleting the log files, for linux to empty the space from disk.
I see that killall -KILL closes the process by its name, but what is the opposite - the run command?
Calling it by its name without any command seems to not work. I will be glad for any tips, thank you.
Debian uses systemd to manage processes. You should, therefore, use the systemd's commands to stop and start rsyslogd.
systemctl stop rsyslog
and
systemctl start rsyslog
If you are using really old versions of Debian (so old that you should upgrade), it may be possible that sys V is still used. In that case, there is a file under /etc/init.d which is called rc.rsyslog or something comparable (use ls /etc/init.d to find the exact name). In that case, it would be
sudo /etc/init.d/rc.rsyslog stop
and
sudo /etc/init.d/rc.rsyslog start
Or it may be, that your systemd-package may be broken. In that case, the package can be re-installed:
apt-get --reinstall install systemd
To start rsyslogd:
systemctl start rsyslog
To stop it:
systemctl stop rsyslog
If you want to do both, use
systemctl restart rsyslog
I am on arch linux, accessing an account on a server over SSH. I have run a bash script containing recursion that results in an infinite loop of "no such file or directory" which continues despite any interrupt command ctrl C etc, it is totally uninterruptible. This eventually results in an endless stream of bash: fork: No child processes. I cannot execute any commands whilst this happens, and when it stops with "Resource temporarily unavailable", i am unable to execute any commands to kill the script because "bash: fork: No child processes" starts up again. I have no idea what to do, any help?
ps doesn't work
Looks like you've caused a fork bomb. You can try the methods here to stop it, but you'll most likely end up needing to reboot.
Run kill -9 -1 from the user login that caused the forkbomb . No need to reboot.
PS: Consult your seniors before running it on Prod server
1) ps faux (find PID and place in second command)
2) kill [PID]
If any virus attack then again this process come so you need to enable virus scanner on cpanel and scan and remove.
Important:
Hosting providers must install the following services for this interface to appear:
The ClamAV Scanner plugin in WHM’s Manage Plugins interface (WHM >> Home >> cPanel >> Manage Plugins).
The Exim Mail Server service on the server in WHM’s Service Manager interface (WHM >> Home >> Service Configuration >> Service Manager).
Run ps faux (you might need to run it from other user or with sudo) and search for the offending process (may look like a big branch of the tree)
If needed, kill the process via its PID
Why do we use /etc/init.d/httpd start in the below program? Why can't we use service httpd start? For me it's showing as unrecognized service. (I have installed httpd already.)
#!/bin/bash
if (( $(ps -ef | grep httpd | wc -l) > 1 ))
then
echo "httpd is running!!!"
else
/etc/init.d/httpd start
fi
:-) vishal I don't mean to frustrate you. However, it's difficult to answer your question without a lot of assumptions.
Some considerations for not using /etc/init.d/httpd start
hard-coded location
assumes that httpd is stored in file /etc/init.d/httpd and not say apache2 or nginx or something else.
even the ps -ef test assumes the process name to be httpd and sometimes it's not
Some considerations for not using service httpd start
There may also be good reasons for not using service httpd start in this script because it may have side effects. For example,
service may not have httpd registered as a service
if you use service you may end up relaunching other dependent services which you may not want to do
service may bury the errors during start up and you may want to.
I have this protocol port open to read remotely from Python, PHP applications but daily it crash and the port is unavailable as a result Python, PHP all client application fails
$ cat /var/tmp/server.sh
#!/bin/bash
while true; do tail -f /usr/local/freeswitch/log/freeswitch.log | nc -l -p 9999 -q 1 &
Q. Is there anyway to make this script always running like service this start or stop and if its crashed that somehow it automatically again get restarted ? Any advise or link to do such thing? i am using CentOS 6.x
Put your script in /etc/inittab as following
id:1:respawn:/var/tmp/server.sh
Refer to http://linux.about.com/od/commands/l/blcmdl5_inittab.htm for more information about the /etc/initab file.
After editing /etc/inittab restart your system.
I'm trying to ensure a script remains running on a development server. It collates stats and provides a web service so it's supposed to persist, yet a few times a day, it dies off for unknown reasons. When we notice we just launch it again, but it's a pain in the rear and some users don't have permission (or the knowhow) to launch it up.
The programmer in me wants to spend a few hours getting to the bottom of the problem but the busy person in me thinks there must be an easy way to detect if an app is not running, and launch it again.
I know I could cron-script ps through grep:
ps -A | grep appname
But again, that's another hour of my life wasted on doing something that must already exist... Is there not a pre-made app that I can pass an executable (optionally with arguments) and that will keep a process running indefinitely?
In case it makes any difference, it's Ubuntu.
I have used a simple script with cron to make sure that the program is running. If it is not, then it will start it up. This may not be the perfect solution you are looking for, but it is simple and works rather well.
#!/bin/bash
#make-run.sh
#make sure a process is always running.
export DISPLAY=:0 #needed if you are running a simple gui app.
process=YourProcessName
makerun="/usr/bin/program"
if ps ax | grep -v grep | grep $process > /dev/null
then
exit
else
$makerun &
fi
exit
Then add a cron job every minute, or every 5 minutes.
Monit is perfect for this :)
You can write simple config files which tell monit to watch e.g. a TCP port, a PID file etc
monit will run a command you specify when the process it is monitoring is unavailable/using too much memory/is pegging the CPU for too long/etc. It will also pop out an email alert telling you what happened and whether it could do anything about it.
We use it to keep a load of our websites running while giving us early warning when something's going wrong.
-- Your faithful employee, Monit
Notice: Upstart is in maintenance mode and was abandoned by Ubuntu which uses systemd. One should check the systemd' manual for details how to write service definition.
Since you're using Ubuntu, you may be interested in Upstart, which has replaced the traditional sysV init. One key feature is that it can restart a service if it dies unexpectedly. Fedora has moved to upstart, and Debian is in experimental, so it may be worth looking into.
This may be overkill for this situation though, as a cron script will take 2 minutes to implement.
#!/bin/bash
if [[ ! `pidof -s yourapp` ]]; then
invoke-rc.d yourapp start
fi
If you are using a systemd-based distro such as Fedora and recent Ubuntu releases, you can use systemd's "Restart" capability for services. It can be setup as a system service or as a user service if it needs to be managed by, and run as, a particular user, which is more likely the case in OP's particular situation.
The Restart option takes one of no, on-success, on-failure, on-abnormal, on-watchdog, on-abort, or always.
To run it as a user, simply place a file like the following into ~/.config/systemd/user/something.service:
[Unit]
Description=Something
[Service]
ExecStart=/path/to/something
Restart=on-failure
[Install]
WantedBy=graphical.target
then:
systemctl --user daemon-reload
systemctl --user [status|start|stop|restart] something
No root privilege / modification of system files needed, no cron jobs needed, nothing to install, flexible as hell (see all the related service options in the documentation).
See also https://wiki.archlinux.org/index.php/Systemd/User for more information about using the per-user systemd instance.
I have used from cron "killall -0 programname || /etc/init.d/programname start". kill will error if the process doesn't exist. If it does exist, it'll deliver a null signal to the process (which the kernel will ignore and not bother passing on.)
This idiom is simple to remember (IMHO). Generally I use this while I'm still trying to discover why the service itself is failing. IMHO a program shouldn't just disappear unexpectedly :)
Put your run in a loop- so when it exits, it runs again... while(true){ run my app.. }
I couldn't get Chris Wendt solution to work for some reason, and it was hard to debug. This one is pretty much the same but easier to debug, excludes bash from the pattern matching. To debug just run: bash ./root/makerun-mysql.sh. In the following example with mysql-server just replace the value of the variables for process and makerun for your process.
Create a BASH-script like this (nano /root/makerun-mysql.sh):
#!/bin/bash
process="mysql"
makerun="/etc/init.d/mysql restart"
if ps ax | grep -v grep | grep -v bash | grep --quiet $process
then
printf "Process '%s' is running.\n" "$process"
exit
else
printf "Starting process '%s' with command '%s'.\n" "$process" "$makerun"
$makerun
fi
exit
Make sure it's executable by adding proper file permissions (i.e. chmod 700 /root/makerun-mysql.sh)
Then add this to your crontab (crontab -e):
# Keep processes running every 5 minutes
*/5 * * * * bash /root/makerun-mysql.sh
The supervise tool from daemontools would be my preference - but then everything Dan J Bernstein writes is my preference :)
http://cr.yp.to/daemontools/supervise.html
You have to create a particular directory structure for your application startup script, but it's very simple to use.
first of all, how do you start this app? Does it fork itself to the background? Is it started with nohup .. & etc? If it's the latter, check why it died in nohup.out, if it's the first, build logging.
As for your main question: you could cron it, or run another process on the background (not the best choice) and use pidof in a bashscript, easy enough:
if [ `pidof -s app` -eq 0 ]; then
nohup app &
fi
You could make it a service launched from inittab (although some Linuxes have moved on to something newer in /etc/event.d). These built in systems make sure your service keeps running without writing your own scripts or installing something new.
It's a job for a DMD (daemon monitoring daemon). there are a few around; but I usually just write a script that checks if the daemon is running, and run if not, and put it in cron to run every minute.
Check out 'nanny' referenced in Chapter 9 (p197 or thereabouts) of "Unix Hater's Handbook" (one of several sources for the book in PDF).
A nice, simple way to do this is as follows:
Write your server to die if it can't listen on the port it expects
Set a cronjob to try to launch your server every minute
If it isn't running it'll start, and if it is running it won't. In any case, your server will always be up.
I think a better solution is if you test the function, too. For example, if you had to test an apache, it is not enough only to test, if "apache" processes on the systems exist.
If you want to test if apache OK is, then try to download a simple web page, and test if your unique code is in the output.
If not, kill the apache with -9 and then do a restart. And send a mail to the root (which is a forwarded mail address to the roots of the company/server/project).
It's even simplier:
#!/bin/bash
export DISPLAY=:0
process=processname
makerun="/usr/bin/processname"
if ! pgrep $process > /dev/null
then
$makerun &
fi
You have to remember though to make sure processname is unique.
One can install minutely monitoring cronjob like this:
crontab -l > crontab;echo -e '* * * * * export DISPLAY=":0.0" && for
app in "eiskaltdcpp-qt" "transmission-gtk" "nicotine";do ps aux|grep
-v grep|grep "$app";done||"$app" &' >> crontab;crontab crontab
disadvantage is that the app names you enter have to be found in ps aux|grep "appname" output and at same time being able to be launched using that name: "appname" &
also you can use the pm2 library.
sudo apt-get pm2
And if its a node app can install.
Sudo npm install pm2 -g
them can run the service.
linux service:
sudo pm2 start [service_name]
npm service app:
pm2 start index.js