Thursday, June 2, 2016

[Quick Tips: Reser Root Password]: reset root user password rhel7 Centos 7

reset root user password rhel7 Centos 7

reset root user password rhel7 and centos 7.  Some times if you forgot root user password, you can’t reset root user password from any other user since Linux is not allowed to reset the root user password from other Normal / Administrator user.
If your going to write RHCSA (Red hat Certified System Administrator) and RHCE (Red hat Certified Engineer) certifications this is the first step you have to resolve.

reset root user password procedure

Authentication Failure
When you type wrong password above authentication failure screen will appear. Then in the top right corner there is a power button will appear as shown in below screenshot, click on power button then click restart
restart server click on power button
Click Restart
Server will restart.
press e to edit arkit
When server is loading boot menu then press any key (Arrow Key / Space Bar) to stop the boot menu, then press ‘e’ to edit the kernel line. Whenever kernel lines are edited below screen will appear
ctrl s
in kernel line where you see “linux16” word go to end of that line and type rd.break console=tty1then press CTRL+X
server will continue to boot in single user mode. File system in this mode will be in Read Only mode. So we have to remount the file system as Read / Write then only we can able to make a change in configuration files. when we change an Password of root user encrypted password will be stored in /etc/shadow.
remount as read write file system
switch_root# mount -o remount,rw /sysroot
above command will mount an file system as read-write
switch_root# chroot /sysroot
above command will change as actual root
sh-4.2# passwd
above command will change the password of root user
Now root password is changed. 
Note: In RHEL7 by default SELinux is in enforcing state so we have to relabel the SELinux then only server will boot properly when you reboot to do that follow the below steps
sh-4.2# touch /.autorelabel
Above mentioned command will create an hidden file under the slash which means SELinux will auto matically relabel the SELinux policy when server is booting.
That’s it After the successful boot of server use new password to login.

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