Install Oracle JDK

Go to the link : http://www.oracle.com/technetwork/java/javase/downloads/

Accept the license agreement and Download the tar.gz file (eg: jdk -8u65-linux-i586.tar.gz)

Extract the file using the command tar -xzvf jdk-8u65-linux-i586.tar.gz

Copy the extracted directory (In my case jdk1.8.0_65) to the required location say /scratch

alternatives –install /usr/bin/java java /scratch/jdk1.8.0_65/bin/java 20000

alternatives –config java

You can see the list of available java versions and select our installed one by typing the number corresponding to that one.

Run a script at boot time in CentOS 7

By default /etc/rc.local and /etc/rc.d/rc.local are no longer executable in CentOS7 with the new systemd-changes. Follow the below steps to make the script /root/g.sh run at boot time:

1. chmod +x /etc/rc.d/rc.local
2. chmod +x /root/g.sh
2. Mention your script at the bottom of the file /etc/rc.local (/etc/rc.local is a symlink to /etc/rc.d/rc.local)as below :

sh /root/g.sh

Restart and check 🙂

Reset the password from single user mode in CentOS7

While booting up your machine, select the existing kernel and press ‘e’

Replace the entry ‘ro‘ with ‘rw init=/sysroot/bin/sh’

changed to

Press ctrl+x to save and start single user mode using the bash shell we mentioned above.

Run the below command and change password after that:

chroot /sysroot

passwd

Update selinux parameters as below :

touch /.autorelabel

Now reboot your machine. It may take some time to apply the apply the changes while booting up.

Thanks 🙂

Check whether the server is virtual or physical

1. Install the package : facter
In centOS : yum install facter
In ubuntu : apt-get install facter
2. Run the command :

facter virtual

3. Check the output.

for example :

[root@test1 ~]# facter virtual
vmware

root@test2:~# facter virtual
physical

Thanks 🙂

Change the color of your terminal

To change the color of the terminal :

tput setaf number

Use the below numbers for the corresponding color.

Black : 0
Red : 1
Green : 2
Yellow : 3
blue : 4
Magenta : 5
Cyan : 6
White : 7

Eg : For Green(my fav :)),

tput setaf 2

Enjoy 🙂

Import certificate and key into jks

1. First create a p12 file and import both the certificate and key into it using openssl.

openssl pkcs12 -export -name theg -in /etc/ssl/certs/theg.crt -inkey /etc/ssl/private/theg.key -out theg.p12

2.Convert the p12 format into jks format using keytool :

keytool -importkeystore -destkeystore theg.jks -srckeystore theg.p12 -srcstoretype pkcs12 -alias theg

Note : Here I used the name theg for my certificates and alias, change it accordingly.

Plugin ‘InnoDB’ registration as a STORAGE ENGINE failed.

I got the below error while restarting mysql service after updating the my.cnf file :

 [ERROR] Plugin ‘InnoDB’ init function returned error.
 [ERROR] Plugin ‘InnoDB’ registration as a STORAGE ENGINE failed.
 [ERROR] Unknown/unsupported storage engine: INNODB
 [ERROR] Aborting 

Just followed the below steps to resolve the issue :

cd /var/lib/mysql
mv ibdata1 ib_logfile0 ib_logfile1 /tmp/

Note that my datadir was /var/lib/mysql. Change the location accordingly.

service mysqld restart

[root@theg-01 mysql]# service mysqld restart
Stopping mysqld:                                           [  OK  ]
Starting mysqld:                                           [  OK  ]

Thats it 🙂