MacOS – How much free space does fsck need to rebuild the catalog file

That's either a disk on it's way out or something has been corrupted and the OS is having problems mounting the drive.

Do you have your system disk? If so, you could try booting into is by holding the C key while booting and run Disk Utility, then do a permissions repair and a disk repair if you can.

What fsck command did you enter? fsck -f ? If not then you should try that too.

If you can get into single-user mode then you can run the following command to repair permissions:

sudo diskutil repairPermissions /

Honestly, you don't mess around with these messages. I think that the first thing to do is to make sure you have a complete backup of your hard drive. Get a second drive with enough capacity. Use Carbon Copy Cloner or Time Machine, or Super Duper to copy the drive.

Once you have a backup, you could easily reformat the drive, (this will avoid bad sectors), and then copy back from the backup.

My 2¢ Hope this helps..