Script for CentOS to restart MySQL service whenever it is stopped - mysql

I want to write a script for restart MySQL service whenever it is in stopped status.
I don't know how to write the IF statement on this script.

#vastlysuperiorman
if [ ! $(ps aux | grep mysql) ]
then
service mysql restart
fi
First, don't forget to protect your operand. See this reminder : bash : Illegal number
Then, you could simplify by :
[[ $(ps -ef | grep [m]ysql) ]] || service mysql restart
(I prefere to use ps -ef because it's more POSIX compliant even if I always use [[ instead of test or [ in Bash).
Finaly, it's better to check the status with service mysql status. You could try something like instead :
[[ $(service mysql status) =~ running ]] || service mysql restart
#user33398
You could try to use this test in a loop or with watch command for example. Or you could use more smart tools like cron or jenkins or nagios to do that.

No sense re-inventing the wheel. There are great software solutions out there that can do this for you. Monit is a good open source example.
If you do opt to write a script, a simple solution could be to do something like the following:
if [ ! $(ps aux | grep mysql) ]
then
service mysql restart
fi

Related

Is there a command line tool that will auto pretty-print json?

I know that tools like 'jq' can let you add a pipe to the command and format it, but you can't use it for situations like displaying real time json logs from a local server. Is there a tool that can achieve that?
I assume you use a default linux distribution with systemd installed, and all services will communicate with systemd to make protocol entries.
Back in the days linux created log files only, but they got to big. Then they added logrotate to keep it a bit more clean.
A up to date linux distribution uses systemd to store protocol entries, which is much better.
To read a protocol you need to find the service you are looking for first.
To list all services connected with systemd call ...
systemctl list-units | grep service
You could use it without grep if you really cant use pipes.
Anyway, pick the service you like and call its protocol via journalctl. Here are some examples ...
journalctl -u ssh.service -p warning -n 30 # (sudo) last 30 warnings and errors SSH created
journalctl -u apache2.service -p err --no-pager # (sudo) all Apache entries without using the pager (less)
journalctl -k -p err --since today # (sudo) kernel error messages of today
Add the option -o json or -o json-pretty to it and you will have the output you wanted. You can also add option -F or --follow to show most recent journal entries, and continuously print new entries as they are appended to the journal. This way you could make cool backgrounds with conky for example.
You can also get the status of your service via systemctl ...
systemctl status apache2.service # (sudo) status of Apache
This way you can pretty print ...
real time json logs from a local server
like you wanted, and without using jq ...
admin#suse:~$ journalctl -u apache2.service -p warning -n 1 -o json-pretty --no-pager
{
"__CURSOR" : "s=65cbb17b253f44c0b800cee690cfb9ee;i=187fd;b=d3effa777ddf4ba9b4f82f126be4439e;m=51cb2bb2d53;t=54b7c4c9ffbeb;x=9fd3b1bc1e50a798",
"__REALTIME_TIMESTAMP" : "1490372117134315",
"__MONOTONIC_TIMESTAMP" : "5620815834451",
"_BOOT_ID" : "d3effa777ddf4ba9b4f82f126be4439e",
"_TRANSPORT" : "syslog",
"_SYSTEMD_SLICE" : "system.slice",
"_MACHINE_ID" : "dc3b59f36cc34cfa8873c5b530577a2a",
"_HOSTNAME" : "suse",
"SYSLOG_FACILITY" : "1",
"_UID" : "33",
"_GID" : "33",
"PRIORITY" : "4",
"SYSLOG_IDENTIFIER" : "/usr/lib/cgi-bin/captainlog/search.sh",
"MESSAGE" : "Request for the specified frontend is not possible. REMOTE_ADDR: xxxx:xxx:xxxx:xxxx:xxxx:xxxx:xxx:xxxx",
"_COMM" : "logger",
"_CAP_EFFECTIVE" : "0",
"_SYSTEMD_CGROUP" : "/system.slice/apache2.service",
"_SYSTEMD_UNIT" : "apache2.service",
"SYSLOG_PID" : "21314",
"_PID" : "21314",
"_SOURCE_REALTIME_TIMESTAMP" : "1490372117133991"
}
Here is a good guide I found on the internet.

userparameters and ZBX_NOTSUPPORTED

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.

Shell script to check if mysql is up or down

I want a bash shell script that i can run using a cron job to check if mysql on a remote server is running. If it is, then do nothing, other start the server.
The cronjob will be checking the remote server for a live (or not) mysql every minute. I can write the cron job myself, but i need help with the shell script that checks if a remote mysql is up or down. The response after a check if up or down is not important. But the check is important.
You can use below script
#!/bin/bash
USER=root
PASS=root123
mysqladmin -h remote_server_ip -u$USER -p$PASS processlist ###user should have mysql permission on remote server. Ideally you should use different user than root.
if [ $? -eq 0 ]
then
echo "do nothing"
else
ssh remote_server_ip ###remote server linux root server password should be shared with this server.
service mysqld start
fi
The script in the selected answer works great, but requires that you have the MySQL client installed on the local host. I needed something similar for a Docker container and didn't want to install the MySQL client. This is what I came up with:
# check for a connection to the database server
#
check=$(wget -O - -T 2 "http://$MYSQL_HOST:$MYSQL_PORT" 2>&1 | grep -o mariadb)
while [ -z "$check" ]; do
# wait a moment
#
sleep 5s
# check again
#
check=$(wget -O - -T 2 "http://$MYSQL_HOST:$MYSQL_PORT" 2>&1 | grep -o mariadb)
done
This is a little different, in that it will loop until a database connection can be made. I am also using MariaDB instead of the stock MySQL database. You can change this by changing the grep -o mariadb to something else - I'm not sure what MySQL returns on a successful connection, so you'll have to play with it a bit.

how to reinitialize the database

I have downloaded a demo copy of Hybris for evaluation purposes, and it has been more than 30 days since I downloaded it, and recently I tried to restart it, but it would not, and instead gave me the following message:
"This licence is only for demo or develop usage and is valid for 30 days.
After this time you have to reinitialize database to continue your work."
I am/have been running it on a Mac, and the database is MySQL...
What (UNIX) commands do I use to re-initialise the database, so that I can start up the Hybris Server?
Using command line in the Terminal application - goto YOURPATH/hybris/bin/platform and run the ant clean all then ant initialize command then start hybris:
1) Goto your platform directory
cd $YOURPATH/hybris/bin/platform
2) Set ant's environment by runing "dot" "space" "dot-slash" setantenv.sh
. ./setantenv.sh
3) Then run ant clean all (to clean environment)
ant clean all
4) then run ant initialize (to re-initialize environment)
ant initialize
5) Re-start the hybris server process by running hybrisserver.sh
./hybrisserver.sh
6) have a nice rest of your day! (if this helped you then please give an UP vote - thanks!)
:)
you can use Ant command ant initialize and error will go away
Ant initialize would removes tables that exists in Hybris items.xml files? If you want to reset your DB i have a script that i use across various projects (can be found here, on GitHub)
#!/bin/bash
MUSER="$1"
MPASS="$2"
MDB="$3"
# Detect paths
MYSQL=$(which mysql)
AWK=$(which awk)
GREP=$(which grep)
if [ $# -ne 3 ]
then
echo "Usage: $0 {MySQL-User-Name} {MySQL-User-Password} {MySQL-Database-Name}"
echo "Drops all tables from a MySQL"
exit 1
fi
TABLES=$($MYSQL -u $MUSER -p$MPASS $MDB -e 'show tables' | $AWK '{ print $1}' | $GREP -v '^Tables' )
for t in $TABLES
do
echo "Deleting $t table from $MDB database..."
$MYSQL -u $MUSER -p$MPASS $MDB -e "drop table $t"
done
You need to reinitialize, [ant all] and rebuild hybris as you have did in first time:
Reason : Evaluation copy works only for 30 days and after it will be expired.
When you start your server it will show in console like below image. Pls Check.
Yo can also use Hybris Administration Console to initialization
Platfrom -> Initialization

Issues with MySQL restart on running through a crontab scheduler

I have written a shell script which starts MySQL when its killed/terminated. I am running this shell script using a crontab.
My cron looks for the script file named mysql.sh under /root/mysql.sh
sh /root/mysql.sh
mysql.sh:
cd /root/validate-mysql-status
sh /root/validate-mysql-status/validate-mysql-status.sh
validate-mysql-status.sh:
# mysql root/admin username
MUSER="xxxx"
# mysql admin/root password
MPASS="xxxxxx"
# mysql server hostname
MHOST="localhost"
MSTART="/etc/init.d/mysql start"
# path mysqladmin
MADMIN="$(which mysqladmin)"
# see if MySQL server is alive or not
# 2&1 could be better but i would like to keep it simple
$MADMIN -h $MHOST -u $MUSER -p${MPASS} ping 2>/dev/null 1>/dev/null
if [ $? -ne 0 ]; then
# MySQL's status log file
MYSQL_STATUS_LOG=/root/validate-mysql-status/mysql-status.log
# If log file not exist, create a new file
if [ ! -f $MYSQL_STATUS_LOG ]; then
cat "Creating MySQL status log file.." > $MYSQL_STATUS_LOG
now="$(date)"
echo [$now] error : MySQL not running >> $MYSQL_STATUS_LOG
else
now="$(date)"
echo [$now] error : MySQL not running >> $MYSQL_STATUS_LOG
fi
# Restarting MySQL
/etc/init.d/mysql start
now1="$(date)"
echo [$now1] info : MySQL started >> $MYSQL_STATUS_LOG
cat $MYSQL_STATUS_LOG
fi
When I run the above mysql shell script manually using webmin's crontab, MySQL started successfully (when its killed).
However, when I schedule it using a cron job, MySQL doesn't starts. The logs are printed properly (it means my cron runs the scheduled script successfully, however MySQL is not restarting).
crontab -l displays:
* * * * * sh /root/mysql.sh
I found from URL's that we should give absolute path to restart MySQL through schedulers like cron. However, it haven't worked for me.
Can anyone please help me!
Thank You.
First, crontab normaly looks like this:
* * * * * /root/mysql.sh
So remove the surplus sh and put it at the beginning of the script - #!/bin/bash I suppose (why are you referring to sh instead of bash?) and don't forget to have an execute permission on the file (chmod +x /root/mysql.sh)
Second, running scripts within crontab is tricky, because the environment is different! You have to set it manually. We start with PATH: go to console and do echo $PATH, and then copy-paste the result into export PATH=<your path> to your cron script:
mysql.sh:
#!/bin/bash
export PATH=.:/bin:/usr/local/bin:/usr/bin:/opt/bin:/usr/games:./:/sbin:/usr/sbin:/usr/local/sbin
{
cd /root/validate-mysql-status
/root/validate-mysql-status/validate-mysql-status.sh
} >> OUT 2>> ERR
Note that I also redirected all the output to files so that you don't receive emails from cron.
Problem is how to know which other variables (besides PATH) matter. Try to go through set | less and try to figure out which variables might be important to set in the cron script too. If there are any MYSQL related variables, you must set them! You may also examine the cron script environment by putting set > cron.env to the cron script and then diff-ing it against console environment to look for significant differences.