We have a Linux Daemon in c and a bash script to start it. The daemon sometimes fail to start because of some configuration file errors but the script reports the daemon was started successfully. A snippet of the script is shown as below, could someone tell me what's wrong with the script?
...
case "$1" in
start)
echo -n "Starting Demo Daemon: "
sudo -u demouser env DEMO_HOME=$DEMO_HOME /usr/local/demouser/bin/democtl startup > /dev/null 2> /dev/null
if [ "$?" = "0" ]; then
echo_success
else
echo_failure
fi
echo
;;
...
Thanks!
I feel there is nothing wrong with the script,it is the reponsibility of daemon to return non zero exit status if failed to start properly and based on those the script will display the message.(which i think it does)
You can add following line in your script to get running status of your Linux Daemon
status=`ps -aef |grep "\/usr\/local\/demouser\/bin\/democtl" |grep -v grep|wc -l`
if [ "$status" = "1" ]; then
echo_success
else
echo_failure
fi
Related
I wrote a node.js application and have written a bash script to start it and verify if it's running. I have my script run npm start & first, then I have a check to see if the ports I want open are open using netstat. The check works fine when I run it after the script is run, but during the running of the script, the check fails because the server has not fully started before the check is run. My code is below:
echo "Starting the server..."
npm start & > /dev/null 2>&1
if [[ -z $(sudo netstat -tulpn | grep :$portNum | grep node) ]] ; then
echo -e "\tPort $portNum is not in use, something went wrong. Exiting."
else
echo -e "\tPort $portNum is in use!"
fi
Is there a good way to take the above script and change it so that the check doesn't occur until the server is fully started? I don't want to use sleep if I can help it.
You can use a wait call:
echo "Starting the server..."
npm start & > /dev/null 2>&1
wait
if [[ -z $(sudo netstat -tulpn | grep :$portNum | grep node) ]] ; then
echo -e "\tPort $portNum is not in use, something went wrong. Exiting."
else
echo -e "\tPort $portNum is in use!"
fi
The only limitation to this is that if npm daemonizes itself then it's no longer a child of the script so the wait command will have no effect (the reason for this is that a process daemonizes itself by terminating and spawning a new process that inherits its role).
I am having this script which looks for the process filebeat and restarts it if is not running. Cron runs this script every 5 minutes. Most of the time this works fine except sometime it creates multiple filebeat process. Can someone please point out what is the issue in my script.
#!/bin/bash
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
service=filebeat
servicex=/usr/share/filebeat/bin/filebeat
pid=`pgrep -x "filebeat"`
if [ $pid > /dev/null ]
then
echo "$(date) $service is running!!!"
else
echo "$(date) starting $service"
cd /home/hpov/beats/filebeat
./filebeat -c filebeat.yml &
fi
#!/bin/bash
pidof script.x86 >/dev/null
if [[ $? -ne 0 ]] ; then
echo "Restarting script: $(date)" >> /var/log/script.txt
/etc/script/script.x86 &
fi
Super easy :D
I have BBB based custom Embedded Linux based board with busybox shell(ash)
I have a situation where my script must run in background with following condition
There must only one instance of the script.
wrapper script need to know if script started successfully in background or not.
There is another wrapper script which starts and stops my script, wrapper script is as mentioned below.
#!/bin/sh
export PATH=/bin:/sbin:/usr/bin:/usr/sbin
readonly TEST_SCRIPT_PATH="/home/testscript.sh"
readonly TEST_SCRIPT_LOCK_PATH="/var/run/${TEST_SCRIPT_PATH##*/}.lock"
start_test_script()
{
local pid_of_testscript=0
local status=0
#Run test script in background
"${TEST_SCRIPT_PATH}" &
#---------Now When this point is hit, lock file must be created.-----
if [ -f "${TEST_SCRIPT_LOCK_PATH}" ];then
pid_of_testscript=$(head -n1 ${TEST_SCRIPT_LOCK_PATH})
if [ -n "${pid_of_testscript}" ];then
kill -0 ${pid_of_testscript} &> /dev/null || status="${?}"
if [ ${status} -ne 0 ];then
echo "Error starting testscript"
else
echo "testscript start successfully"
fi
else
echo "Error starting testscript.sh"
fi
fi
}
stop_test_script()
{
local pid_of_testscript=0
local status=0
if [ -f "${TEST_SCRIPT_LOCK_PATH}" ];then
pid_of_testscript=$(head -n1 ${TEST_SCRIPT_LOCK_PATH})
if [ -n "${pid_of_testscript}" ];then
kill -0 ${pid_of_testscript} &> /dev/null || status="${?}"
if [ ${status} -ne 0 ];then
echo "testscript not running"
rm "${TEST_SCRIPT_LOCK_PATH}"
else
#send SIGTERM signal
kill -SIGTERM "${pid_of_testscript}"
fi
fi
fi
}
#Script starts from here.
case ${1} in
'start')
start_test_script
;;
'stop')
stop_test_script
;;
*)
echo "Usage: ${0} [start|stop]"
exit 1
;;
esac
Now actual script "testscript.sh" looks something like this,
#!/bin/sh
#Filename : testscript.sh
export PATH=/bin:/sbin:/usr/bin:/usr/sbin
set -eu
LOCK_FILE="/var/run/${0##*/}.lock"
FLOCK_CMD="/bin/flock"
FLOCK_ID=200
eval "exec ${FLOCK_ID}>>${LOCK_FILE}"
"${FLOCK_CMD}" -n "${FLOCK_ID}" || exit 0
echo "${$}" > "${LOCK_FILE}"
# >>>>>>>>>>-----Now run the code in background---<<<<<<
handle_sigterm()
{
# cleanup
"${FLOCK_CMD}" -u "${FLOCK_ID}"
if [ -f "${LOCK_FILE}" ];then
rm "${LOCK_FILE}"
fi
}
trap handle_sigterm SIGTERM
while true
do
echo "do something"
sleep 10
done
Now in above script you can see "---Now run the code in background--" at that point I am sure that either lock file is successfully created or instance of this script is already running. So Then I can safely run other code in background and wrapper script can check for lockfile and find out if the process mentioned in the lock file is running or not.
can shellscript itself make it to run in background ?
if not is there a better way to meet all the conditions ?
I think you can look into job control built-in, specifically bg.
Job Control Commands
When processes say they background themselves, what they actually do is fork and exit the parent. You can do the same by running whichever commands, functions or statements you want with & and then exiting.
#!/bin/sh
echo "This runs in the foreground"
sleep 3
while true
do
sleep 10
echo "doing background things"
done &
According to the documentation, an exec does not modify the pid of a process.
I'm using a service to lauch my process, and aim to get his pid to save him in /var/run/.
For that i use $!.
My init script make a call to a .sh file that does an exec to an other .sh file. This file then make an exec call to java.
In the end, the pid the java app has is not the one I get in my init script. Why ?
Note : when i make only one sh script that does exec java, that works. But I don't see why adding one exec would change anything.
Code if it can help understanding.
Init script:
$DAEMON > /var/local/red5/log/jvm.stdout 2>&1 &
RETVAL=$?
if [ $RETVAL -eq 0 ]; then
echo $! > $PIDFILE
fi
$DAEMON calls :
if [ -z "$RED5_HOME" ]; then export RED5_HOME=`pwd`; fi
ulimit -n 32767
# start Red5
exec /bin/bash $RED5_HOME/red5.sh > $RED5_HOME/log/jvm.stdout 2>&1 &
And my red5.sh calls java : (with a few exports before that)
# start Red5
exec "$JAVA" "$JYTHON" -Dred5.root="${RED5_HOME}" $JAVA_OPTS -cp "${RED5_CLASSPATH}" "$RED5_MAINCLASS" $RED5_OPTS
Works if i do :
if [ -z "$RED5_HOME" ]; then export RED5_HOME=`pwd`; fi
ulimit -n 32767
# start Red5
exec "$JAVA" "$JYTHON" -Dred5.root="${RED5_HOME}" $JAVA_OPTS -cp "${RED5_CLASSPATH}" "$RED5_MAINCLASS" $RED5_OPTS
Result :
pid via ps -ef: 15950.
pid with $! : 15947
Any idea ?
Thank you.
Your original $DAEMON is starting another new process when you call exec as a background process, so your Java program does run in a separate process than the background process started in the init script. Just run exec with
if [ -z "$RED5_HOME" ]; then export RED5_HOME=`pwd`; fi
ulimit -n 32767
# start Red5
# CHANGE: no ampersand at the end of this line
exec /bin/bash $RED5_HOME/red5.sh > $RED5_HOME/log/jvm.stdout 2>&1
You submit your job in the background when appending a & character, and thus it gets its own new pid.
EDIT: Thanks for the downvote. I meant this line:
exec /bin/bash $RED5_HOME/red5.sh > $RED5_HOME/log/jvm.stdout 2>&1 &
I have a Perl script that I want to daemonize. Basically this perl script will read a directory every 30 seconds, read the files that it finds and then process the data. To keep it simple here consider the following Perl script (called synpipe_server, there is a symbolic link of this script in /usr/sbin/) :
#!/usr/bin/perl
use strict;
use warnings;
my $continue = 1;
$SIG{'TERM'} = sub { $continue = 0; print "Caught TERM signal\n"; };
$SIG{'INT'} = sub { $continue = 0; print "Caught INT signal\n"; };
my $i = 0;
while ($continue) {
#do stuff
print "Hello, I am running " . ++$i . "\n";
sleep 3;
}
So this script basically prints something every 3 seconds.
Then, as I want to daemonize this script, I've also put this bash script (also called synpipe_server) in /etc/init.d/ :
#!/bin/bash
# synpipe_server : This starts and stops synpipe_server
#
# chkconfig: 12345 12 88
# description: Monitors all production pipelines
# processname: synpipe_server
# pidfile: /var/run/synpipe_server.pid
# Source function library.
. /etc/rc.d/init.d/functions
pname="synpipe_server"
exe="/usr/sbin/synpipe_server"
pidfile="/var/run/${pname}.pid"
lockfile="/var/lock/subsys/${pname}"
[ -x $exe ] || exit 0
RETVAL=0
start() {
echo -n "Starting $pname : "
daemon ${exe}
RETVAL=$?
PID=$!
echo
[ $RETVAL -eq 0 ] && touch ${lockfile}
echo $PID > ${pidfile}
}
stop() {
echo -n "Shutting down $pname : "
killproc ${exe}
RETVAL=$?
echo
if [ $RETVAL -eq 0 ]; then
rm -f ${lockfile}
rm -f ${pidfile}
fi
}
restart() {
echo -n "Restarting $pname : "
stop
sleep 2
start
}
case "$1" in
start)
start
;;
stop)
stop
;;
status)
status ${pname}
;;
restart)
restart
;;
*)
echo "Usage: $0 {start|stop|status|restart}"
;; esac
exit 0
So, (if I have well understood the doc for daemon) the Perl script should run in the background and the output should be redirected to /dev/null if I execute :
service synpipe_server start
But here is what I get instead :
[root#master init.d]# service synpipe_server start
Starting synpipe_server : Hello, I am running 1
Hello, I am running 2
Hello, I am running 3
Hello, I am running 4
Caught INT signal
[ OK ]
[root#master init.d]#
So it starts the Perl script but runs it without detaching it from the current terminal session, and I can see the output printed in my console ... which is not really what I was expecting. Moreover, the PID file is empty (or with a line feed only, no pid returned by daemon).
Does anyone have any idea of what I am doing wrong ?
EDIT : maybe I should say that I am on a Red Hat machine.
Scientific Linux SL release 5.4 (Boron)
Thanks,
Tony
I finally re-wrote the start function in the bash init script, and I am not using daemon anymore.
start() {
echo -n "Starting $pname : "
#daemon ${exe} # Not working ...
if [ -s ${pidfile} ]; then
RETVAL=1
echo -n "Already running !" && warning
echo
else
nohup ${exe} >/dev/null 2>&1 &
RETVAL=$?
PID=$!
[ $RETVAL -eq 0 ] && touch ${lockfile} && success || failure
echo
echo $PID > ${pidfile}
fi
}
I check that the pid file is not existing already (if so, just write a warning). If not, I use
nohup ${exe} >/dev/null 2>&1 &
to start the script.
I don't know if it is safe this way (?) but it works.
The proper way to daemonize a process is have it detach from the terminal by itself. This is how most larger software suites do it, for instance, apache.
The rationale behind daemon not doing what you would expect from its name, and how to make a unix process detach into the background, can be found here in section 1.7 How do I get my program to act like a daemon?
Simply invoking a program in the background isn't really adequate for
these long-running programs; that does not correctly detach the
process from the terminal session that started it. Also, the
conventional way of starting daemons is simply to issue the command
manually or from an rc script; the daemon is expected to put itself
into the background.
For further reading on this topic: What's the difference between nohup and a daemon?
According to man daemon correct syntax is
daemon [options] -- [command] [command args]
Your init script startup should run something like:
daemon --pidfile ${pidfile} -- ${exe}
As said here, it seems that the process needs to be sent to the background using &.
Daemon don’t do it for you.