If you want to disable host key checking for ansible adhoc command, first run the the command below.
[root@server ~]# export ANSIBLE_HOST_KEY_CHECKING=FalseNow, once you have disabled host key checking run your ansible ad-hoc command.
[root@server ~]# ansible all -i inventory -m shell -a 'uptime'What is exit status in the linux?
Whenever you fire a shell command it returns a status to check if that command was successful or not – exit status can be very useful in scripts to make you scripts stable.
Example:-
In the example below, I ran uptime command and it was successful – so when I checked the exit status using echo $? it showed 0.
[root@server ~]# uptime
05:15:27 up 50 days, 16:53, 1 user, load average: 0.08, 0.03, 0.08
[root@server ~]# echo $?
0
[root@server ~]#
Now let’s see what happens when command is not successful.
So in the example below, I typed incorrect command and exit status was other than 0 – which indicates error.
[root@server ~]# uptimee
-bash: uptimee: command not found
[root@server ~]# echo $?
127
[root@server ~]#
Practical usage in shell scripting.
#!/bin/bash
cd $1 > /dev/null 2>&1
if [ $? != 0 ]
then
echo "Directory Not Found" ; exit
fi
echo "Great!"
So, above script terminates if cd command is not successful.
If it’s successful it will execute further code.
[root@server ~]# ./exitstatus.sh /tmp
Great!
[root@server ~]# ./exitstatus.sh /tmpp
Directory Not Found
[root@server ~]#
So you are running you own webserver which at the times is short of resources and the services like MySQL and HTTPD stops – results your website is down until you get a chance to fix it.
Quick solution would be to implement a script which restarts services at such situations and emails you that the service was restarted – so you can later go and check what was the problem
So below is the script, which will make sure that HTTP , MySQL and Postfix is running all the time – It will check status of the service and if it’s stopped or Dead it will restart it.
How to Implement this Script ?
Setup a cron to run the script every minute – like below.
* * * * * root /home/bob/scripts/servicecheck.shCreate a file called servicecheck.sh and put the code below.
Just change the email address in the script to yours and you are done.
#!/bin/bash
#####################
#MySQL CHECK
#####################
/sbin/service mariadb status > /var/log/mysqlservicestatus 2>&1
STATUS=$(cat /var/log/mysqlservicestatus | egrep 'dead|failed')
if [[ $STATUS = "" ]]
then
/bin/logger -t MYSQL IS RUNNING
else
/sbin/service mariadb restart
/bin/logger -t restarted mysql
echo "Restarted MYSQL" | /bin/mail -s "Restarted MYSQL" you@email.com
fi
echo > /var/log/mysqlservicestatus
#####################
#HTTPD CHECK
#####################
/sbin/service httpd status > /var/log/httpdservicestatus 2>&1
STATUS=$(cat /var/log/httpdservicestatus | egrep 'dead|failed')
if [[ $STATUS = "" ]]
then
/bin/logger -t httpd IS RUNNING
else
/sbin/service httpd restart
/bin/logger -t restarted httpd
echo "Restarted HTTPD" | /bin/mail -s "Restarted HTTPD" you@email.com
fi
echo > /var/log/httpdservicestatus
#####################
#POSTFIX CHECK
#####################
/sbin/service postfix status > /var/log/postfixservicestatus 2>&1
STATUS=$(cat /var/log/postfixservicestatus | egrep 'dead|failed')
if [[ $STATUS = "" ]]
then
/bin/logger -t postfix IS RUNNING
else
/sbin/service postfix restart
/bin/logger -t restarted postfix
echo "Restarted postfix" | /bin/mail -s "Restarted postfix" you@email.com
fi
You want to monitor other services, just go ahead and add it.
First we will see what is Array in Linux
If you have been doing shell scripting, you must have definitely came across the term called variable. So when you use a variable, you can add a single name to the variable – In other words one variable can hold only one value.
Example of an Variable
#!/bin/bash
cityname="Berlin"
echo "$cityname"So if you want to hold names of multiple cities, then you will have to create new variable for each city.
For an Example
cityname01="Berlin"
cityname02="Tokyo"
cityname03="Moscow"
cityname04="Rio"
cityname05="Denver"However, to ease life we could use a single Array which could hold up all values in a single variable.
To define Array :-
cityname[0]="Berlin"
cityname[1]="Tokyo"
cityname[2]="Moscow"
cityname[3]="Rio"
cityname[4]="Denver"So here we have stored all city Names in a Array called “cityname”. So now question is how do you access an Array.
You just need to echo it’s number 🙂 Like shown below.
#!/bin/bash
cityname[0]="Berlin"
cityname[1]="Tokyo"
cityname[2]="Moscow"
cityname[3]="Rio"
cityname[4]="Denver"
echo "${cityname[3]}"So above script will print “Rio” If you want to print all city names then you would use
echo "${cityname[@]}"
OR
echo "${cityname[*]}"You can copy paste the script below and run it which will help you understand better.
#!/bin/bash
cityname[0]="Berlin"
cityname[1]="Tokyo"
cityname[2]="Moscow"
cityname[3]="Rio"
cityname[4]="Denver"
echo Cities I love are : "${cityname[@]}"
Output would be.
Cities I love are : Berlin Tokyo Moscow Rio Denver