How to reset a lost root password on CentOS 7?
Jun 30, 2025 am 12:09 AMTo reset the root password of CentOS 7, go to the GRUB menu and start single user mode. 1. Press the arrow keys repeatedly during startup to interrupt the startup process to enter the GRUB menu; 2. Select the kernel and press "e" to edit the startup parameters; 3. Add rd.break at the end of line 16 of Linux, and then start; 4. After entering the initramfs shell, remount the root file system to read and write mode; 5. Use chroot to switch to the real root environment and use passwd root to modify the password; 6. Create a .autorelabel file to ensure that SELinux relabel correctly; 7. Enter exit to exit and restart the system. This method requires physical or console access, and the remote server needs to pay attention to using the correct console method. After completion, you can log in with your new password.
If you've lost the root password on a CentOS 7 system, don't panic — it's possible to reset it without reinstalling the OS. The process involves booting into single-user mode via the GRUB menu and changing the password from there. It's straightforward but requires physical or console access.
Accessing the GRUB Menu
CentOS 7 uses GRUB2 as its bootloader, and the first step is interrupting the boot process so you can enter the GRUB menu.
- As the system boots up, start tapping the arrow keys (usually any arrow key works) before the boot countdown finishes.
- This will stop the automatic boot and bring up the GRUB menu.
- If your system boots too fast, try holding down the arrow key during startup.
Once in the GRUB menu, select the kernel you want to boot (probably the top one), then press "e" to edit the boot configuration.
Editing the Kernel Command Line
Inside the GRUB editor, you'll see several lines of configuration. You need to modify the kernel line:
- Find the line that starts with
linux16
, usually around the middle of the screen. - At the end of that line, add
rd.break
— this tells the system to pause before mounting the root filesystem. - Then press Ctrl X or F10 to boot with this modified setting.
This will drop you into a minimum shell called the "emergency mode" or initramfs shell.
Remounting Root Filesystem Read-Write
At this point, the root filesystem is mounted read-only. You need to turn it with write access:
- Run:
mount -o remount,rw /sysroot
- Then use the
chroot
command to switch into the real root environment:chroot /sysroot
Now you're inside the system's environment and can change the root password using the standard passwd
command:
passwd root
You'll be prompted to type and confirm the new password.
After setting the password, it's important to relabel SELinux contexts, otherwise the system might get stuck on reboot:
touch /.autorelabel
Exit the chroot environment by typing exit
, then reboot the system with reboot
.
Final Notes
The system should now boot normally, and you can log in with the new root password.
One thing people often forget is that if the system doesn't have a graphic interface or if you're connecting via a remote console, getting into GRUB can feel unfamiliar. Make sure you know how your system boots — for example, cloud VMs might require using a serial console instead of a regular keyboard.
Also, keep in mind that this method requires local access, which is why physical security matters for servers.
Basically that's all— once you've done it once, it becomes second nature.
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