SLE12 Boot exits to dracut emergency shell

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Environment

SUSE Linux Enterprise Server 12

Situation

The server hangs at boot time with a screen similar to:

[  OK  ] Started Show Plymouth Boot Screen.
[  OK  ] Reached target Paths.
[  OK  ] Reached target Basic System.
[    6.990557] sd 30:0:0:0: [sda] Assuming drive cache: write through

If allowed to wait for up to five minutes, the hang condition will change to an emergency shell with something similar to:

   Starting Dracut Emergency Shell...
Warning: /dev/sdb1 does not exist

Generating "/run/initramfs/rdsosreport.txt"
[   199.368656] end_request: I/O error, dev fd0, sector 0

Entering emergency mode. Exit the shell to continue.

dracut:/#

Running the "journalctl" command reveals the following errors:

dracut-initqueue[189]: Warning: Count not boot.
dracut-initqueue[189]: Warning: /dev/sdb1 does not exist

Tailing the "/run/initramfs/rdsosreport.txt" yields the same dracut-initqueue errors.

The /etc/default/grub contains the following line:

GRUB_CMDLINE_LINUX_DEFAULT=" root=/dev/sdb1 resume=/dev/sda1 splash=silent quiet showopts"

Resolution

1. Boot from the installation media and select Rescue System
2. Mount the root device to /mnt
3. Mount the boot device to /mnt/boot (# Many times the root and boot devices are the same)
4. Bind the rescue system's proc, sys and dev to /mnt. For example,
# for i in proc sys dev; do mount --rbind /$i /mnt/$i; done
5. Chroot to /mnt
# chroot /mnt
6. Edit the /etc/default/grub file and remove or set a correct root= path in the GRUB_CMDLINE_LINUX_DEFAULT variable.
7. Save /etc/default/grub
8. Run grub2-mkconfig -o /boot/grub2/grub.cfg.
9. Reboot the server normally.

Cause

An invalid root= kernel parameter set in the grub2 configuration file. In this case root=/dev/sdb1 had to be removed or changed to root=/dev/sda2 in the /etc/default/grub file.

Disclaimer

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