[Solved] Fedora/CentOS emergency prompt after boot.

October 11th, 2016 by Andrea Matesi 246 Views

Recently, one of my backup servers started complaining - during its latest reboot, I ended up with an emergency boot prompt loop!

The server was a Fedora (but the workaround should also apply to almost every CentOS, Ubuntu and maybe to other distros too!).

Why no regular boot up?

Here's a 'shot of what I got:

I'll paste the error for the search engines:

*** An error occurred during the file system check.
*** Dropping you to a shell; the system will reboot
*** when you leave the shell.
Give root password for maintenance
(or type control-D to continue):

By interpreting the above error, it seems there's an issue while checking the filesystems.

The md arrays looks alright ("clean"), although there's a problem with /dev/sdc1 ("No such file or directory while opening /dev/sdc1").

IMHO, it's a good practice to keep an external HDD plugged (and maybe also rsync'ed).

As I discovered with my work-mates, that was the case, 'though (for reasons unknown), it seems the external HDD had been removed.

I also discovered the external HDD automount was (manually) hardcoded in fstab.

In conclusion, to fix the issue, I had to patch fstab.

'Thoug I couldn't edit fstab since the "slash" was mounted Read-Only.

After searching through endless posts and forums (OK, I may have used the wrong terms...), I just found what I needed:

mount -n -o remount,rw /

The above command mounted the ROOT (aka slash), as a READ-WRITE filesystem.

After mounting slash in RW-mode, I was able to manually patch fstab, namely, by commenting out the offending drive.

MOUNT-command details.

The "-n" parameter prevents the mount command to populate the mtab lines (while mounting devices).

The "-o" parameter is a switch to specify additional, comma-separated options (similar to the options used inside fstab - ie. 'defaults', 'sync', 'noatime', etc.).

The "remount" option tries to remount the fs as-is (since it is already mounted RO).

Finally, the "rw" option enables read & write mode for the desired filesystem.

Once done, I rebooted the backup box and ta-daaa! (Windows 3.1 welcome sound): onsite backup server back online.

Senior Professional Network and Computer Systems Engineer during work hours and father when home.

Andrea strives to deliver outstanding customer service and heaps of love towards his family.

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