Changing/ Recovering root user password in RHEL7/ Cent OS 7

We are going to see How to Changing/ Recovering root user password in RHEL7/ CentOS 7 in this post

Boot the system and wait for GRUB menu. On some Operating systems, you need to disturb the booting by pressing any keys in your system.

Changing/ Recovering root user password in RHEL7/ Cent OS 7
Highlight the first line which is pointing the Operating System entry like showed in the above image and press “e” key in your keyboard to edit manually.
Then will get the below screen.
Using up/down, left/right arrow keys move the cursor to the “rhgb quiet” which is in kernel line starting with “linux16”
Using delete/backspace keys manually delete “rhgb quiet” entry and append “init=/bin/bash” entry like below.

Than press Ctrl+x  to reboot your OS with specified option. Once rebooted, will get a shell prompt without credentials.

check whether the root filesystem has been mounted or not.

Mount the root filesystem with RW permission.

Now issue the “passwd” command to recover/change the root password. It will ask for the new password and re-enter the password for confirmation. Once provided the new password will receive the “Authentication token successfully updated”

Relabel the SELinux content using below command.
Restart the machine using the below command.
Finally, we recovered the root password. Now will restart the machine and login with a new root password.

Configuring LVM in redhat

For LVM Configuration need to follw the below steps.

1. Partition creation
2. Physical volume creation
3. Volume group creation
4. Logical volume creation

Here i’m using /dev/sda and /dev/sdb hard disks


/dev/sda – 500GB
/dev/sdb – 500GB

I already shared the steps to create partitions in previous post.

Click here to create new partition/filesystem in a physical disk.

Using fdisk we have to change the partition type by changing the ID.

For that we should use “t” option to change the partition type. Once we executed this, it will ask for
the Hex code of partition type. Here we need to mention “8e” as Hex code for LVM partition type.

Note: change the partition type for all HDD/ Partitions which we are going to configure LVM.

Than follow the below steps for LVM configuration.

Next we have to create physical volumes using below mentioned commands.

#pvcreate /dev/sda1 /dev/sdb1

#vgcreate -s 16M newvg /dev/sda1 /dev/sdb1

“newvg” is new volume group name and /dev/sda1, /dev/sdb1 will be added in this volume group.
Now this two hard disks will act as a single hard disk and the new size of hard disk is 1000GB.

Next we have to create logical volumes over the volume group, which is like a partitioning here.

#lvcreate -n lv1 -L 200G newvg

-n:  This option is to mention the new logical volume group.
lv1: new logical volume group name.
-L:  this option is to mention the size of new logical volume.

Now we have created logical volume and we should format and mount the lv.

#mkfs.xfs /dev/newvg/lv1

directory is required to mount the lv.

#mkdir /data

#mount /dev/newvg/lv1 /data

Now we successfully configured LVM. Follow the lvcreate steps to create more lv’s.