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Reset Password in Linux

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This text provides instructions on how to reset the root password for CentOS 4, 5, 6, and 7, as well as Ubuntu and Debian systems. It includes different methods for each operating system, involving editing kernel options and using single user mode to change the root password. The text also mentions the need to update system information and reboot the system after resetting the password.

Reset root password#

CentOS 4, 5, 6#

Press 'e' after rhgb quit, add 1 or single
Press Enter to save, press 'b' to boot and modify password with passwd

CentOS 7#

Method 1#

Enter grub2 and press 'e' to edit. Scroll down to the linux16 line and delete rhgb, quiet, and LANG parameters. To easily move to the end of the line, press ctrl+e. To move to the beginning of the line, press ctrl+a. The linux16 line will be linuxefi on UEFI systems.

#linux16 /vmlinuz-3.10.0-327.el7.x86_64 root=/dev/mapper/centos-root \ ro rd.lvm.lv=centos/root rd .lvm.lv=centos/swap rd.break
linux16 /vmlinuz-3.10.0-327.el7.x86_64 root=/dev/mapper/centos-root \ rw init=/sysroot/bin/sh rd.lvm.lv=centos/root rd .lvm.lv=centos/swap rd.break
Press ctrl+x to enter single user mode

#mount -o remount,rw  /sysroot
chroot /sysroot
# restorecon /etc/shadow
passwd root
# Update system information
touch /.autorelabel
exit
reboot

Method 2#

rw init=/bin/bash
linux16 /vmlinuz-3.10.0-327.el7.x86_64 root=/dev/mapper/centos-root \
 ro rd.lvm.lv=centos/root rd.lvm.lv=centos/swap rw init=/bin/bash
Press ctrl+x
/usr/sbin/load_policy -i
mount -o remount,rw /
passwd root
exec /sbin/init 3

# Method 3-gpt
Reset root password on CentOS 7:

1. Restart your CentOS 7 server and select the Kernel from the GRUB menu.
2. Press 'e' to edit the Kernel option.
3. Find the line starting with "linux16" and change "ro" at the end to "rw init=/sysroot/bin/sh".
4. Press "Ctrl + X" to start the CentOS 7 system.
5. When in single user mode, run the following commands:

chroot /sysroot
passwd root
  1. Enter a new root password and confirm.
  2. Run the following command to apply the changes:
touch /.autorelabel
  1. Reboot CentOS 7:
exit
reboot

Reset root password on Ubuntu:

  1. Restart your Ubuntu system and select the Kernel from the GRUB menu.
  2. Press 'e' to edit the Kernel option.
  3. Find the line starting with "linux" and change "ro quiet splash $vt_handoff" at the end to "rw init=/bin/bash".
  4. Press "Ctrl + X" to start the Ubuntu system.
  5. Ubuntu will automatically start bash as the root user. Enter the following command:
passwd root
  1. Enter a new root password and confirm.
  2. Reboot Ubuntu:
reboot

Reset root password on Debian:

  1. Restart your Debian system and select the Kernel from the GRUB menu.
  2. Press 'e' to edit the Kernel option.
  3. Find the line starting with "linux" and change "ro quiet" at the end to "rw init=/bin/bash".
  4. Press "Ctrl + X" to start the Debian system.
  5. Debian will automatically start bash as the root user. Enter the following command:
passwd root
  1. Enter a new root password and confirm.
  2. Reboot Debian:
reboot
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