Redhat 8 Boot Single User Mode via Serial Console

To boot into single user mode via the serial console you need to edit grub before it boots.

When it starts booting you will see the grub menu, before it starts hit the “e” key to edit. You will see something similar as below. Change the information to whats shown below in BOLD

set gfx_payload=keep
insmod gzio
linux ($root)/vmlinuz-0-rescue-2e2ae80928c8406ca64a9b3427ec91a6 root=/dev/mapp\
er/rhel-root ro crashkernel=auto resume=/dev/mapper/rhel-swap\
oot console=tty0 console=ttyS0,115200 rd.break
initrd ($root)/initramfs-0-rescue-2e2ae80928c8406ca64a9b3427ec91a6.img

Press Ctrl-x to start, Ctrl-c for a command prompt or Escape to
discard edits and return to the menu. Pressing Tab lists
possible completions.

Once you boot enter the following to make your partition default and writable. Then do what you need to do.                                             

Everything is under /sysroot
Make it writable: mount -w -o remount /

Thats it, be careful you have full root privledges.