I want to execute action once in a day. Like whenever day's 1st alert is present in the Zabbix that time Action will restart the service/process. After that suppose same alert is come in Zabbix that time no Action will performed that time.
I am using Zabbix version 6.2.4 and on client side it is zabbix-agent2
I have created the Action on the trigger.
item --> get information process is running or not.
system.run["ps -aux | grep -i 'proces' | grep -v 'grep' | wc -l"]
trigger --> When process is down that time trigger id generated.
last(/Monitor process/system.run["ps -aux | grep -i 'proces' | grep -v 'grep' | wc -l"])<1
0 indicate --> Through the alert in Zabbix
1 indicate --> do not do anything.
Action --> When trigger is present in the Zabbix Action execute the service start script.
Up to this point all function is working fine.
But I want this action only once in a day. Like whenever day's 1st alert is present in the Zabbix that time Action will restart the service/process.
Problem history is not available as an Action condition, so you don't know in Zabbix if the Event already triggered, and when. You can however manage it inside the restart script.
Following script restarts the service when it's been more than 24 hours since last restart.
#!/bin/bash
SEMAPHORE=/tmp/zabbix.service1.lastrestart
first_time=0
day=$(expr 24 \* 60 \* 60)
delta=$(expr $(date +%s) - $(stat -c %Y $SEMAPHORE 2>/dev/null) 2>/dev/null)
if [ -z "$delta" ]; then
# file doesn't exists
first_time=1
elif [ $delta -gt $day ] ; then
# more than 1d since last restart
first_time=1
fi
if [ $first_time -eq 1 ]; then
systemctl restart service1
touch $SEMAPHORE
fi
Please note that system.run[] is deprecated, you should use it for tests only. In this case the appropriate key may be proc.num[], or even systemd.unit.info[] since you are using Agent2 newer than 4.4 (see https://www.zabbix.com/documentation/6.2/en/manual/discovery/low_level_discovery/examples/systemd?hl=systemd).
I have a pretty simple script that is something like the following:
#!/bin/bash
VAR1="$1"
MOREF='sudo run command against $VAR1 | grep name | cut -c7-'
echo $MOREF
When I run this script from the command line and pass it the arguments, I am not getting any output. However, when I run the commands contained within the $MOREF variable, I am able to get output.
How can one take the results of a command that needs to be run within a script, save it to a variable, and then output that variable on the screen?
In addition to backticks `command`, command substitution can be done with $(command) or "$(command)", which I find easier to read, and allows for nesting.
OUTPUT=$(ls -1)
echo "${OUTPUT}"
MULTILINE=$(ls \
-1)
echo "${MULTILINE}"
Quoting (") does matter to preserve multi-line variable values; it is optional on the right-hand side of an assignment, as word splitting is not performed, so OUTPUT=$(ls -1) would work fine.
$(sudo run command)
If you're going to use an apostrophe, you need `, not '. This character is called "backticks" (or "grave accent"):
#!/bin/bash
VAR1="$1"
VAR2="$2"
MOREF=`sudo run command against "$VAR1" | grep name | cut -c7-`
echo "$MOREF"
Some Bash tricks I use to set variables from commands
Sorry, there is a loong answer, but as bash is a shell, where the main goal is to run other unix commands and react on result code and/or output, ( commands are often piped filter, etc... ).
Storing command output in variables is something basic and fundamental.
Therefore, depending on
compatibility (posix)
kind of output (filter(s))
number of variable to set (split or interpret)
execution time (monitoring)
error trapping
repeatability of request (see long running background process, further)
interactivity (considering user input while reading from another input file descriptor)
do I miss something?
First simple, old (obsolete), and compatible way
myPi=`echo '4*a(1)' | bc -l`
echo $myPi
3.14159265358979323844
Compatible, second way
As nesting could become heavy, parenthesis was implemented for this
myPi=$(bc -l <<<'4*a(1)')
Using backticks in script is to be avoided today.
Nested sample:
SysStarted=$(date -d "$(ps ho lstart 1)" +%s)
echo $SysStarted
1480656334
bash features
Reading more than one variable (with Bashisms)
df -k /
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/dm-0 999320 529020 401488 57% /
If I just want a used value:
array=($(df -k /))
you could see an array variable:
declare -p array
declare -a array='([0]="Filesystem" [1]="1K-blocks" [2]="Used" [3]="Available" [
4]="Use%" [5]="Mounted" [6]="on" [7]="/dev/dm-0" [8]="999320" [9]="529020" [10]=
"401488" [11]="57%" [12]="/")'
Then:
echo ${array[9]}
529020
But I often use this:
{ read -r _;read -r filesystem size using avail prct mountpoint ; } < <(df -k /)
echo $using
529020
( The first read _ will just drop header line. ) Here, in only one command, you will populate 6 different variables (shown by alphabetical order):
declare -p avail filesystem mountpoint prct size using
declare -- avail="401488"
declare -- filesystem="/dev/dm-0"
declare -- mountpoint="/"
declare -- prct="57%"
declare -- size="999320"
declare -- using="529020"
Or
{ read -a head;varnames=(${head[#]//[K1% -]});varnames=(${head[#]//[K1% -]});
read ${varnames[#],,} ; } < <(LANG=C df -k /)
Then:
declare -p varnames ${varnames[#],,}
declare -a varnames=([0]="Filesystem" [1]="blocks" [2]="Used" [3]="Available" [4]="Use" [5]="Mounted" [6]="on")
declare -- filesystem="/dev/dm-0"
declare -- blocks="999320"
declare -- used="529020"
declare -- available="401488"
declare -- use="57%"
declare -- mounted="/"
declare -- on=""
Or even:
{ read _ ; read filesystem dsk[{6,2,9}] prct mountpoint ; } < <(df -k /)
declare -p mountpoint dsk
declare -- mountpoint="/"
declare -a dsk=([2]="529020" [6]="999320" [9]="401488")
(Note Used and Blocks is switched there: read ... dsk[6] dsk[2] dsk[9] ...)
... will work with associative arrays too: read _ disk[total] disk[used] ...
Other related sample: Parsing xrandr output: and end of Firefox tab by bash in a size of x% of display size? or at AskUbuntu.com Parsing xrandr output
Dedicated fd using unnamed fifo:
There is an elegent way! In this sample, I will read /etc/passwd file:
users=()
while IFS=: read -u $list user pass uid gid name home bin ;do
((uid>=500)) &&
printf -v users[uid] "%11d %7d %-20s %s\n" $uid $gid $user $home
done {list}</etc/passwd
Using this way (... read -u $list; ... {list}<inputfile) leave STDIN free for other purposes, like user interaction.
Then
echo -n "${users[#]}"
1000 1000 user /home/user
...
65534 65534 nobody /nonexistent
and
echo ${!users[#]}
1000 ... 65534
echo -n "${users[1000]}"
1000 1000 user /home/user
This could be used with static files or even /dev/tcp/xx.xx.xx.xx/yyy with x for ip address or hostname and y for port number or with the output of a command:
{
read -u $list -a head # read header in array `head`
varnames=(${head[#]//[K1% -]}) # drop illegal chars for variable names
while read -u $list ${varnames[#],,} ;do
((pct=available*100/(available+used),pct<10)) &&
printf "WARN: FS: %-20s on %-14s %3d <10 (Total: %11u, Use: %7s)\n" \
"${filesystem#*/mapper/}" "$mounted" $pct $blocks "$use"
done
} {list}< <(LANG=C df -k)
And of course with inline documents:
while IFS=\; read -u $list -a myvar ;do
echo ${myvar[2]}
done {list}<<"eof"
foo;bar;baz
alice;bob;charlie
$cherry;$strawberry;$memberberries
eof
Practical sample parsing CSV files:
As this answer is loong enough, for this paragraph,
I just will let you refer to
this answer to How to parse a CSV file in Bash?, I read a file by using an unnamed fifo, using syntax like:
exec {FD}<"$file" # open unnamed fifo for read
IFS=';' read -ru $FD -a headline
while IFS=';' read -ru $FD -a row ;do ...
... But using bash loadable CSV module.
On my website, you may find the same script, reading CSV as inline document.
Sample function for populating some variables:
#!/bin/bash
declare free=0 total=0 used=0 mpnt='??'
getDiskStat() {
{
read _
read _ total used free _ mpnt
} < <(
df -k ${1:-/}
)
}
getDiskStat $1
echo "$mpnt: Tot:$total, used: $used, free: $free."
Nota: declare line is not required, just for readability.
About sudo cmd | grep ... | cut ...
shell=$(cat /etc/passwd | grep $USER | cut -d : -f 7)
echo $shell
/bin/bash
(Please avoid useless cat! So this is just one fork less:
shell=$(grep $USER </etc/passwd | cut -d : -f 7)
All pipes (|) implies forks. Where another process have to be run, accessing disk, libraries calls and so on.
So using sed for sample, will limit subprocess to only one fork:
shell=$(sed </etc/passwd "s/^$USER:.*://p;d")
echo $shell
And with Bashisms:
But for many actions, mostly on small files, Bash could do the job itself:
while IFS=: read -a line ; do
[ "$line" = "$USER" ] && shell=${line[6]}
done </etc/passwd
echo $shell
/bin/bash
or
while IFS=: read loginname encpass uid gid fullname home shell;do
[ "$loginname" = "$USER" ] && break
done </etc/passwd
echo $shell $loginname ...
Going further about variable splitting...
Have a look at my answer to How do I split a string on a delimiter in Bash?
Alternative: reducing forks by using backgrounded long-running tasks
In order to prevent multiple forks like
myPi=$(bc -l <<<'4*a(1)'
myRay=12
myCirc=$(bc -l <<<" 2 * $myPi * $myRay ")
or
myStarted=$(date -d "$(ps ho lstart 1)" +%s)
mySessStart=$(date -d "$(ps ho lstart $$)" +%s)
This work fine, but running many forks is heavy and slow.
And commands like date and bc could make many operations, line by line!!
See:
bc -l <<<$'3*4\n5*6'
12
30
date -f - +%s < <(ps ho lstart 1 $$)
1516030449
1517853288
So we could use a long running background process to make many jobs, without having to initiate a new fork for each request.
You could have a look how reducing forks make Mandelbrot bash, improve from more than eight hours to less than 5 seconds.
Under bash, there is a built-in function: coproc:
coproc bc -l
echo 4*3 >&${COPROC[1]}
read -u $COPROC answer
echo $answer
12
echo >&${COPROC[1]} 'pi=4*a(1)'
ray=42.0
printf >&${COPROC[1]} '2*pi*%s\n' $ray
read -u $COPROC answer
echo $answer
263.89378290154263202896
printf >&${COPROC[1]} 'pi*%s^2\n' $ray
read -u $COPROC answer
echo $answer
5541.76944093239527260816
As bc is ready, running in background and I/O are ready too, there is no delay, nothing to load, open, close, before or after operation. Only the operation himself! This become a lot quicker than having to fork to bc for each operation!
Border effect: While bc stay running, they will hold all registers, so some variables or functions could be defined at initialisation step, as first write to ${COPROC[1]}, just after starting the task (via coproc).
Into a function newConnector
You may found my newConnector function on GitHub.Com or on my own site (Note on GitHub: there are two files on my site. Function and demo are bundled into one unique file which could be sourced for use or just run for demo.)
Sample:
source shell_connector.sh
tty
/dev/pts/20
ps --tty pts/20 fw
PID TTY STAT TIME COMMAND
29019 pts/20 Ss 0:00 bash
30745 pts/20 R+ 0:00 \_ ps --tty pts/20 fw
newConnector /usr/bin/bc "-l" '3*4' 12
ps --tty pts/20 fw
PID TTY STAT TIME COMMAND
29019 pts/20 Ss 0:00 bash
30944 pts/20 S 0:00 \_ /usr/bin/bc -l
30952 pts/20 R+ 0:00 \_ ps --tty pts/20 fw
declare -p PI
bash: declare: PI: not found
myBc '4*a(1)' PI
declare -p PI
declare -- PI="3.14159265358979323844"
The function myBc lets you use the background task with simple syntax.
Then for date:
newConnector /bin/date '-f - +%s' #0 0
myDate '2000-01-01'
946681200
myDate "$(ps ho lstart 1)" boottime
myDate now now
read utm idl </proc/uptime
myBc "$now-$boottime" uptime
printf "%s\n" ${utm%%.*} $uptime
42134906
42134906
ps --tty pts/20 fw
PID TTY STAT TIME COMMAND
29019 pts/20 Ss 0:00 bash
30944 pts/20 S 0:00 \_ /usr/bin/bc -l
32615 pts/20 S 0:00 \_ /bin/date -f - +%s
3162 pts/20 R+ 0:00 \_ ps --tty pts/20 fw
From there, if you want to end one of background processes, you just have to close its fd:
eval "exec $DATEOUT>&-"
eval "exec $DATEIN>&-"
ps --tty pts/20 fw
PID TTY STAT TIME COMMAND
4936 pts/20 Ss 0:00 bash
5256 pts/20 S 0:00 \_ /usr/bin/bc -l
6358 pts/20 R+ 0:00 \_ ps --tty pts/20 fw
which is not needed, because all fd close when the main process finishes.
As they have already indicated to you, you should use `backticks`.
The alternative proposed $(command) works as well, and it also easier to read, but note that it is valid only with Bash or KornShell (and shells derived from those),
so if your scripts have to be really portable on various Unix systems, you should prefer the old backticks notation.
I know three ways to do it:
Functions are suitable for such tasks:**
func (){
ls -l
}
Invoke it by saying func.
Also another suitable solution could be eval:
var="ls -l"
eval $var
The third one is using variables directly:
var=$(ls -l)
OR
var=`ls -l`
You can get the output of the third solution in a good way:
echo "$var"
And also in a nasty way:
echo $var
Just to be different:
MOREF=$(sudo run command against $VAR1 | grep name | cut -c7-)
When setting a variable make sure you have no spaces before and/or after the = sign. I literally spent an hour trying to figure this out, trying all kinds of solutions! This is not cool.
Correct:
WTFF=`echo "stuff"`
echo "Example: $WTFF"
Will Fail with error "stuff: not found" or similar
WTFF= `echo "stuff"`
echo "Example: $WTFF"
If you want to do it with multiline/multiple command/s then you can do this:
output=$( bash <<EOF
# Multiline/multiple command/s
EOF
)
Or:
output=$(
# Multiline/multiple command/s
)
Example:
#!/bin/bash
output="$( bash <<EOF
echo first
echo second
echo third
EOF
)"
echo "$output"
Output:
first
second
third
Using heredoc, you can simplify things pretty easily by breaking down your long single line code into a multiline one. Another example:
output="$( ssh -p $port $user#$domain <<EOF
# Breakdown your long ssh command into multiline here.
EOF
)"
You need to use either
$(command-here)
or
`command-here`
Example
#!/bin/bash
VAR1="$1"
VAR2="$2"
MOREF="$(sudo run command against "$VAR1" | grep name | cut -c7-)"
echo "$MOREF"
If the command that you are trying to execute fails, it would write the output onto the error stream and would then be printed out to the console.
To avoid it, you must redirect the error stream:
result=$(ls -l something_that_does_not_exist 2>&1)
This is another way and is good to use with some text editors that are unable to correctly highlight every intricate code you create:
read -r -d '' str < <(cat somefile.txt)
echo "${#str}"
echo "$str"
You can use backticks (also known as accent graves) or $().
Like:
OUTPUT=$(x+2);
OUTPUT=`x+2`;
Both have the same effect. But OUTPUT=$(x+2) is more readable and the latest one.
Here are two more ways:
Please keep in mind that space is very important in Bash. So, if you want your command to run, use as is without introducing any more spaces.
The following assigns harshil to L and then prints it
L=$"harshil"
echo "$L"
The following assigns the output of the command tr to L2. tr is being operated on another variable, L1.
L2=$(echo "$L1" | tr [:upper:] [:lower:])
Mac/OSX nowadays come with old Bash versions, ie GNU bash, version 3.2.57(1)-release (arm64-apple-darwin21). In this case, one can use:
new_variable="$(some_command)"
A concrete example:
newvar="$(echo $var | tr -d '123')"
Note the (), instead of the usual {} in Bash 4.
Some may find this useful.
Integer values in variable substitution, where the trick is using $(()) double brackets:
N=3
M=3
COUNT=$N-1
ARR[0]=3
ARR[1]=2
ARR[2]=4
ARR[3]=1
while (( COUNT < ${#ARR[#]} ))
do
ARR[$COUNT]=$((ARR[COUNT]*M))
(( COUNT=$COUNT+$N ))
done
I have this simple script that checks if mysql on remote servers (db-test-1 and db-test-2) is in SST mode and sends a message to a slack channel. The script is running on a third server dedicated for running cron jobs. Here is the code below:
#!/bin/bash
time=$(date);
array=( db-test-1 db-test-2 )
for i in "${array[#]}"
do
S=$(ssh $i ps -ef |grep mysql | grep wsrep_sst_xtrabackup-v2);
if [[ "$S" != "" ]]; then
curl -X POST --data-urlencode "payload={\"channel\": \"#db-share-test\", \"username\": \"wsrep_local_state_comment\", \"text\": \"*$i*: ${time}\n>State transfer in progress, setting sleep higher mysqld\", \"icon_emoji\": \":scorpion:\"}" https://hooks.slack.com/services/G824ZJS9N/B6QS5JEKP/ZjV1hmM1k4dZGsf9HDC1o1jd
exit 0
else
curl -X POST --data-urlencode "payload={\"channel\": \"#db-share-test\", \"username\": \"wsrep_local_state_comment\", \"text\": \"*$i*: ${time}\n>State transfer is complete. Server is Synced now.\", \"icon_emoji\": \":scorpion:\"}" https://hooks.slack.com/services/G824ZJS9N/B6QS5JEKP/ZjV1hmM1k4dZGsf9HDC1o1jd
exit 2
fi
done
The two servers, db-test1 and db-test-2 are part of a PXC cluster. So when i start db-test-1 in SST to join the cluster, i get the following in my slack channel as expected:
*db-test-1*: Sun Aug 27 15:12:44 CST 2017
>State transfer in progress, setting sleep higher mysqld
[3:12]
*db-test-1*: Sun Aug 27 15:12:49 CST 2017
State transfer in progress, setting sleep higher mysqld
[3:12]
*db-test-1*: Sun Aug 27 15:12:51 CST 2017
State transfer in progress, setting sleep higher mysqld
[3:12]
*db-test-1*: Sun Aug 27 15:12:54 CST 2017
State transfer in progress, setting sleep higher mysqld
So the results are being displayed approximately every 3 seconds. However, the cron job executing this script is scheduled to run every minute, hence not sure why it is sending results every 3 seconds or so as shown above.
How can i ensure that the results are displayed every 1 minute to avoid my channel being thrown the same message every 3 seconds? Also, how can i make sure that when the SST is finished, a single message to slack to indicate that the state transfer is finished instead of sending this message none-stop every time the two db servers are not in SST mode?
Besides checking that the cron is properly set, probably something like:
#every_minute /path/to/script
or
*/1 * * * * /path/to/script
It could be also good to ensure that only one occurrence of the program is running, try adding this to your script used within the cron job
*/1 * * * * pgrep script > /dev/null || /path/to/script
or by using something like:
#!/bin/sh
if ps -ef | grep -v grep | grep your_script_name ; then
exit 0
fi
# your code goes below
# ...
I want to ping an external ip from all of my servers that run zabbix agent.
I searched and find some articles about zabbix user parameters.
In /etc/zabbix/zabbix_agentd.conf.d/ I created a file named userparameter_ping.conf with following content:
UserParameter=checkip[*],ping -c4 8.8.8.8 && echo 0 || echo 1
I created an item named checkip in zabbix server with a graph but got no data. After some another digging I found zabbix_get and tested my userparameter but I got the error : ZBX_NOTSUPPORTED
# zabbix_get -s 172.20.4.43 -p 10050 -k checkip
my zabbix version :
Zabbix Agent (daemon) v2.4.5 (revision 53282) (21 April 2015)
Does anybody know what I can do to address this?
After some change and talks with folks in mailing list finally it worked but how :
first i created a file in :
/etc/zabbix/zabbix_agentd.conf.d/
and add this line :
UserParameter=checkip[*],ping -W1 -c2 $1 >/dev/null 2>&1 && echo 0 || echo 1
and run this command :
./sbin/zabbix_agentd -t checkip["8.8.8.8"]
checkip[8.8.8.8] [t|0]
so everything done but Timeout option is very important for us :
add time out in /etc/zabbix/zabbix_agentd.conf
Timeout=30
Timeout default is 3s so if we run
time ping -W1 -c2 8.8.8.8
see maybe it takes more than 3s so you got error :
ZBX_NOTSUPPORTED
It can be anything. For example timeout - default timeout is 3 sec and ping -c4 requires at least 3 seconds, permission/path to ping, not restarted agent, ...
Increase debug level, restart agent and check zabbix logs. Also you can test zabbix_agentd directly:
zabbix_agentd -t checkip[]
[m|ZBX_NOTSUPPORTED] [Timeout while executing a shell script.] => Timeout problem. Edit zabbix_agentd.conf and increase Timeout settings. Default 3 seconds are not the best for your ping, which needs 3+ seconds.
If you need more than 30s for the execution, you can use the nohup (command..) & combo to curb the timeout restriction.
That way, if you generate some file with the results, in the next pass, you can read the file and get back the results without any need to wait at all.
For those who may be experiencing other issues with the same error message.
It is important to run zabbix_agentd with the -c parameter:
./sbin/zabbix_agentd -c zabbix_agentd.conf --test checkip["8.8.8.8"]
Otherwise zabbix might not pick up on the command and will thus yield ZBX_NOTSUPPORTED.
It also helps to isolate the command into a script file, as Zabbix will butcher in-line commands in UserParameter= much more than you'd expect.
I defined two user parameters like this for sync checking between to samba DCs.
/etc/zabbix/zabbix_agentd.d/userparameter_samba.conf:
UserParameter=syncma, sudo samba-tool drs replicate smb1 smb2 cn=schema,cn=configuration,dc=domain,dc=com
UserParameter=syncam, sudo samba-tool drs replicate smb2 smb1 cn=schema,cn=configuration,dc=domain,dc=com
and also provided sudoer access for Zabbix user to execute the command. /etc/sudoers.d/zabbix:
Defaults:zabbix !syslog
Defaults:zabbix !requiretty
zabbix ALL=(ALL) NOPASSWD: /usr/bin/samba-tool
zabbix ALL=(ALL) NOPASSWD: /usr/bin/systemctl
And "EnableRemoteCommands" is enabled on my zabbix_aganetd.conf, sometimes when I run
zabbix_get -s CLIENT_IP -p10050 -k syncma or
zabbix_get -s CLIENT_IP -p10050 -k syncam
I get the error ZBX_NOTSUPPORTED: Timeout while executing a shell script.
but after executing /sbin/zabbix_agentd -t syncam on the client, Zabbix server just responses normally.
Replicate from smb2 to smb1 was successful.
and when it has a problem I get below error on my zabbix.log
failed to kill [ sudo samba-tool drs replicate smb1 smb2 cn=schema,cn=configuration,dc=domain,dc=com]: [1] Operation not permitted
It seems like it is a permission error! but It just resolved after executing /sbin/zabbix_agentd -t syncam but I am not sure the error is gone permanently or will happen at the next Zabbix item check interval.