Single User Mode in CentOS 7 / RHEL 7

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CentOS 7

Single user mode is one of the Run levels in the Linux operating system, Linux operating system has 6 run levels that are used for different requirement or situation. Single user mode mainly used for doing the administrative task such as cleaning the file system, Managing the quotas, Recovering the file system and also recover the lost root password. In this mode services won’t start, none of the users are allowed to login except root, and also system won’t ask for a password to login.

Step 1: While booting you might see the splash screen like below, grub is counting the time to boot the default operating system as mentioned in /etc/grub2.cfg; this time press any key to interrupt the auto boot.

Single User Mode in CentOS 7 - Reset root Password Autoboot
Single User Mode in CentOS 7- Reset root Password Auto boot

Step 2: It will list operating systems (in my case only CentOS installed) that you have installed on the machine, In below that you might find some information about booting the OS and editing the parameters of menu. If you want to enter into single user mode; select the operating system and press “e” edit arguments of kernel.

Single User Mode in CentOS 7 - Reset root password - Select Kernel
Single User Mode in CentOS 7 – Reset root password – Select Kernel

Step 3: Once you have pressed, you should see the information about the selected operating system. It gives you the information about the hard disk and partition where the OS installed, location of the kernel, language, video output, keyboard type, keyboard table, crash kernel and initrd (Initial ram disk).

To enter into single user mode; Go to second last line (Starts with linux 16 or linuxefi) using up and down arrow then  modify the ro argument.

Single User Mode in CentOS 7 - Before changing Kernel Argument RO
Single User Mode in CentOS 7 – Before changing Kernel Argument

Step 5: Modify it to “rw init=/sysroot/bin/sh”. Once done, press “Ctrl+x”

Single User Mode in CentOS 7 - After changing Kernel Argument
Single User Mode in CentOS 7 – After changing Kernel Argument

Now you should be in command line mode with root privileges (without entering password). Now you can start to troubleshoot your system or can do maintenance of your system.

Single User Mode in CentOS 7 - Single user mode
Single User Mode in CentOS 7 – Single user mode

chroot to access your system.

chroot /sysroot

That’s all. You must chroot to reset root password in CentOS 7 / RHEL 7

Further Reading

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Single User Mode in CentOS 7 / RHEL 7

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