RHCSA Version 8: Operating Running Systems

Boot, reboot, and shut down a system normally

Boot systems into different targets manually

Interrupt the boot process in order to gain access to a system

TLDR; 1) Reboot 2) At Grub Menu, select rescue kernel and press e 3) At the end of the linux kernel line, remove rhgb quiet and add rd.break enforcing=0

In order to recover the root password of a system, you must have console access to the server in order to modify the boot loader to boot into single user mode.

When you’re first prompted with the boot menu, press down down arrow on the keyboard to stop the boot timer. Then scroll through your boot menu options until the rescue kernel is highlighted. With the rescue kernel highlighted, press the e button to edit the rescue boot options.

Grub Menu

In the Grub edit menu, locate the line that starts with linux. The command may span multiple lines and will end with rhgb quiet. Go to the end of the line.

Grub Menu: Edit

Remove rhgb quiet from the command and add rd.break enforcing=0. Once complete, press the Ctrl-X key sequence to continue booting to the rescue mode.

Grub Menu:Single User Mode

At this point, the system will boot into single user mode and will boot into a switch_root:/# prompt. The /sysroot filesystem will mount in read-only mode. This can be verified by executing: mount | grep /sysroot. You’ll need to remount the filesystem as read-write. To to this execute, mount -o rw,remount /sysroot. The mount | grep /sysroot command will verify that it’s mounted as read-write.

With the system booted into single user mode and the /sysroot volume mounted with read-write permissions, you will need to change the root to /sysroot. This can be done by executing chroot /sysroot. Once completed, execute the passwd command to change the root password. Once completed type exit twice and the system will reboot. At this point, you will be able to login with the new root password.

When the system has booted back to normal, the security context must be restored for the shadow file. This can be done by executing restorecon /etc/shadow. ls -Z /etc/shadow can be used to view the current security context.

Identify CPU/memory intensive processes and kill processes

Adjust process scheduling

Manage tuning profiles

Locate and interpret system log files and journals

Preserve system journals

Start, stop, and check the status of network services

Securely transfer files between systems