Linux Root Password Recovery Steps on RedHat/Cent OS

Step 1 #> Single User Mode

1. Restart the Server
2. Press Enter in Redhat Enterprise Linux (2.6.32-71.el6_64)
3. Press e edit
4. Select the 2^nd line which will start the word from kernel
5. Press e to edit
6. Type single or s or 1 in end of the line (after rhgb quiet words)
7. Enter
8. Press b to boot in single user mode
9. Shell will come
10. Type the passwd command and enter the new password for root account

Step 2 #> CD Rescue Mode

1. Bash-4.1# This shell is read only so follow the step to read/write mode
2. chroot /mnt/sysimage (This will change the shell to sh-4.1#)
3. Type the passwd command and enter the new password for root account

OR

4. Vim /etc/passwd and delete the x letter only (encypted passwd) in root user line.

Ex: root:x:

Step 3 #> Account Lock Remove

1. Do the same as Single User Mode and run the below command for Unlocking the root user account
2. Shell> passwd –u root

Step 4 #> Password Expiry Remove

1. Go the Single User Mode
2. Shell>chage –l root (To check the account status of root user)
3. If Account expired run the below command
4. Shell>chage –E never

RedHat Linux Grub Password Recovery Steps:

1. If you know the root password just remove the password line from /etc/grub.conf
2. If you know the root password and want to change the grub password do the below steps

Shell> grub-md5-crypt

#copy the encrypted password and paste it in /etc/grub.conf as like below after the line “timeout”

Password - -md5 encryptedpassword

Ex:

default 0
timeout 8
password --md5 $1$lS2dv/$JOcHkLosIn7CJk9xShzzJVw/

3. If you don’t know the grub password and root password do the following steps

#Use the CD Rescue Mode and check the grub.conf file

Shell>vim /boot/grub/grub.conf

#Correct the grub.conf file