The system does not find the root partition, installed on lvm.

Article shows how to solve the issue with missing swap and plymouthd sigrtmin error, when swap is not created as LVM, but as a standard swap.

Boot-Message:

dracut-initqueue[279] Warning: Could not boot
dracut-initqueue[279] Warning; /dev/mapper/rhel_…-root does not exit
sigrtmin+20 from PID 297 plymouthd 

Last error is because of mounting swap failed.

The solution is really simple. Check is standard swap is on with command:

swapon -s

Check where swap is mounted in /etc/fstab

cat /etc/fstab | grep -i swap

If it will show something similar to this:

/dev/sdc    swap swap defaults 0 0

Turn off swap:

swapoff /dev/sdc

Then extend the logical group for example rhel, create logical volume swap in rhel volume group and make a swap on this logical volume:

vgextend rhel /dev/sdc
lvcreate rhel -n swap -L 1024M
mkswap /dev/rhel/swap

Add the following entry in /etc/fstab instead /dev/sdc

/dev/rhel/swap swap swap defaults 0 0

Enable swap

swapon -v /dev/rhel/swap

Example: Change this:

GRUB_CMDLINE_LINUX="rd.lvm.lv=rootVG/root rd.lvm.lv=oldnameVG/swapLV rhgb quiet"

To this:

GRUB_CMDLINE_LINUX="rd.lvm.lv=rootVG/root rd.lvm.lv=rhel/swap rhgb quiet"

When that is completed, you ‘ll want to regenerate the grub config:

grub2-mkconfig -o /boot/grub2/grub.cfg

You can verify that it worked by looking at /boot/grub2/grub.cfg and verifying that swap is now pointed at the correct VG/LV

cat /boot/grub2/grub.cfg

It should contain this:

GRUB_CMDLINE_LINUX="rd.lvm.lv=rootVG/root rd.lvm.lv=rhel/swap rhgb quiet"