Inodes and the superblock

fezzie · 02-26-2010, 04:49 AM

I know that an inode is an area of the disk that contains info about a file. When you remove a file the entry is removed and the inode is marked open for use. What happens when you move a file? Does it retain its inode number or does it get a new unique number? How does this move effect the superblock?

timmeke · 02-26-2010, 05:16 AM

When you move a file, the inode is not changed, because the file is not changed. What does happen, is that the directory's contents (which is a list of inodes) is updated.
The superblock is more used to retain the status of inodes (ie list of free ones that can be recycled). This is thus also not affected
by the file move.
The inode will be updated when you hard link a file (reference count increments) or delete it (ref count decrement and if it turns 0, file
removal + inode freeing).

catkin · 02-26-2010, 05:35 AM

Quote:

Originally Posted by timmeke

When you move a file, the inode is not changed,

as long as the move is within one file system; a move between file systems is, in effect, a copy and a delete.

timmeke · 02-26-2010, 06:01 AM

Yes, you're right, catkin. Thanks for the completion.