Netdata init script for Synology DSM

rc.netdata

#!/bin/bash

# Install this as `/etc/rc.netdata` and call it from `/etc/rc.local`
# to have it executed on boot.

NETDATA_DIR=/opt/netdata
DAEMON=$NETDATA_DIR/bin/srv/netdata
TIMEOUT=30  # seconds to wait for netdata to exit

[ -x $DAEMON ] || exit 0

function get_pid() {
	pid=$( ps ax | grep -v grep | grep -m 1 $DAEMON | awk '{ print $1 }' )
}

function check_netdata() {
	count=1
	while [ $count -lt $TIMEOUT ]; do
		get_pid
		if [ -z $pid ]; then
			break
		else
			sleep 1
			count=$(( $count + 1))
		fi
	done

	if [ $count -eq $TIMEOUT ]; then
		echo "Timeout exceeded waiting for netdata to exit."
		echo "Use '$0 kill' to force netdata to exit."
		exit 1
	fi
}

function stop_netdata() {
	get_pid
	if [ "x$pid" != "x" ]; then
		if [ "x$1" = "xforce" ]; then
			kill -9 $pid
		else
			kill $pid
		fi
	else
		echo "No running netdata found."
	fi

}

function start_netdata() {
	get_pid
	if [ "x$pid" = "x" ]; then
		echo "Starting Netdata."
		$DAEMON
	else
		echo "Netdata already running with pid $pid"
	fi
}

case "$1" in
    start)
		start_netdata
    ;;
    stop)
		echo "Shutting down Netdata."
		stop_netdata
    ;;
	restart)
		echo "Shutting down Netdata."
		stop_netdata
		if [ "x$pid" != "x" ]; then
			echo "Waiting maximum of $TIMEOUT seconds for netdata to exit."
		fi
		check_netdata
		start_netdata
	;;
	kill)
		echo "Killing netdata."
		stop_netdata force
	;;
	status)
		get_pid
		if [ "x$pid" != "x" ]; then
			echo "Netdata running with PID $pid"
		else
			echo "No running netdata found."
		fi
	;;
    *)
        echo "Usage: $0 {start|stop|kill|restart|status}"
        exit 1
esac

exit 0

Hi, @oskapt. We have a link to this file in our documentation. And there is a bug report:

/etc/rc.netdata: line 20: [: 17389: binary operator expected

The problem is get_pid() func returns 2 PIDs:

# ps ax | grep /opt/netdata/bin/srv/netdata | grep -v grep
18652 ?        SNsl 109:21 /opt/netdata/bin/srv/netdata -P /opt/netdata/var/run/netdata/netdata.pid -D
18677 ?        SNl    0:00 /opt/netdata/bin/srv/netdata --special-spawn-server
# ps ax | grep /opt/netdata/bin/srv/netdata | grep -v grep | awk '{ print $1 }'
18652
18677

I think adding -m 1 option to the first grep will fix the issue.

# ps ax | grep -m 1 /opt/netdata/bin/srv/netdata | grep -v grep
18652 ?        SNsl 109:23 /opt/netdata/bin/srv/netdata -P /opt/netdata/var/run/netdata/netdata.pid -D
# ps ax | grep -m 1 /opt/netdata/bin/srv/netdata | grep -v grep | awk '{ print $1 }'
18652

Thanks!

Updated. Thanks for reaching out!

I believe that the modification suggested above can result in the issued command ps ax... being the only result passed to grep -v grep. I've swapped this:
ps ax | grep -m 1 $DAEMON | grep -v grep | awk '{ print $1 }'
with
ps ax | grep -v grep | grep -m 1 $DAEMON | awk '{ print $1 }'

Thoughts?

It's possible, but only if grep -v $DAEMON is earlier in the process list than "$DAEMON" itself. The only way that can happen is if this script is run before netdata is started, in which case netdata isn't running and will be started by the script. Your change doesn't hurt anything, and is probably cleaner from a logical flow. I'll make the adjustment. Thanks for posting it.

I am not sure I follow this part

ps ax | grep -v grep

I am not sure I follow this part

ps ax | grep -v grep

This is standard when grepping for something because the grep command also includes the thing you're grepping for. For example (from something unrelated but that I already had open in my terminal):

root@axigen-0:/axigen/var/log# ps ax | grep entrypoint.sh
      1 pts/0    Ss+    0:00 /bin/bash /axigen/bin/entrypoint.sh
    348 pts/1    S+     0:00 grep --color=auto entrypoint.sh

If I was only looking for lines with entrypoint.sh to find the PID, I need to exclude the grep command that also matches.

Using grep -v grep means, "exclude any line that has grep in it," which assures you that you're only processing the lines you're looking for.

Yeah, I mean the order - ps ax | grep -v grep. Why grep after ps? It does nothing.

On a side note: I usually do the following (first letter in square brackets)

ps ax | grep [e]ntrypoint.sh

• ps ax shows all processes running on the host.
• grep -v grep excludes the grep command
• grep -m 1 $DAEMON returns the first match of whatever is in the variable $DAEMON
• awk '{ print $1 }' returns the first field (which is the pid)

The two grep lines were in the opposite order, which could, in an unusual circumstance, cause the grep line to be matched before $DAEMON and then excluded, resulting in no matches. Flipping it around ensures that only $DAEMON lines are included.

Doing it with square brackets is another way, but it's dependent on the shell. Using grep -v is consistent across any shell I might be working in, or any scripts that I write.

Can you explain why you think that "grep after ps does nothing?"

Ah, you were fixing this

It's possible, but only if grep -v $DAEMON is earlier in the process list than "$DAEMON" itself. The only way that can happen is if this script is run before netdata is started, in which case netdata isn't running and will be started by the script.

I guess I didn't read or understand. So grep -v grep is supposed to filter other grep $DAEMON command that is running at the same time but also started before Netdata. I am not sure this can happen. But thanks for your detailed explanation.

I agree that it's not likely to ever happen, since it would require that the grep command had a pid lower than the running netdata process. However, placing grep -v grep first in the chain changes "unlikely to happen" to "will never happen," and that seemed reasonable.