So, you have removed power before shutting down. The disk could be a little confused. Use "fsck" to fix problems. However this should not be done when the disk is mounted. DO NOT TRY IT. However there is a way to check the FS on boot. There is no need to create a second system disk. Run the check by create a file "/forcefsck" and then reboot. This will cause a disk check to run on startup and minor problems will be repaired. To create the file you may need to use the command "sudo touch /forcefsck". Reboot using "sudo shutdown -r now". (this may have an alias but I only know the long hand version of reboot.) You should see an ASCII progress bar during boot and the file will be removed. If the progress bar is missing and the file still survives you have probably typed it wrong.