Linux Rescue

RedHat/CentOS

• How to recover a root password in Red Hat-based Linux systems

Reset the root's password

For GRUB Bootloader)

系統重開機 -> 進入開機選單

1. Select the kernel
2. Press the e key to edit the entry
3. Select second line (the line starting with the word kernel)
4. Press the e key to edit kernel entry so that you can append single user mode
5. Append the letter S (or word Single) to the end of the (kernel) line
6. Press ENTER key
7. Now press the b key to boot the Linux kernel into single user mode
8. At prompt type passwd command to reset password:

mount -t proc proc /proc
mount -o remount,rw /
passwd
sync
reboot

For LILO Bootloader)

Boot: linux single

passwd
sync
reboot

TIP: 除了 single mode 以外，還有另一個 emergency mode 也可以試試看。

RedHat 8 的環境，輸入的字串改成 systemd.unit=emergency.target , 或 systemd.unit=rescue.target 。