I have disk usage problem with rsync and --link-dest
Incremental backup is taking full disk space:
@localhost media]$ ls
orig
----------------------------------------------------
localhost media]$ du -sh .
25M .
----------------------------------------------------
localhost media]$ rsync -avh orig/ full
----------------------------------------------------
@localhost media]$ du -sh .
49M .
----------------------------------------------------
localhost media]$ echo 1111 > orig/foo111
----------------------------------------------------
localhost media]$ rsync -avh --link-dest=full orig/ orig_1
----------------------------------------------------
localhost media]$ ls orig_1/foo111
orig_1/foo111
_____________________________________________________
localhost media]$ ls full/foo111
ls: cannot access full/foo111: No such file or directory
Everything looks good so far. The latest change is reflected in orig_1
But the directories aren't hard linked and they're all in full size.
-----------------------------------------------------
localhost media]$ du -sh .
74M .
---------------------------------------------
localhost media]$ du -sh orig_1/
25M orig_1/
--------------------------------------------
localhost media]$ du -sh orig
25M orig
---------------------------------------------
localhost media]$ du -sh full
25M full
Am I suppose to have the orig_1 size as 0? And stat command shows no hard links. What am I doing wrong?
When you ran rsync -avh --link-dest=full orig/ orig_1, you ignored this error message (it's more obvious if you remove -v):
--link-dest arg does not exist: full
If we then take a look at man rsync under --link-dest, we find:
If DIR is a relative path, it is relative to the destination directory.
And there it is. full is relative to the current directory. Relative to the destination directory, it would be ../full.
If you try again with rsync -avh --link-dest=../full orig/ orig_1, you get what you expect:
$ du -sh *
149M full
149M orig
232K orig_1
$ du -sh .
298M .
Note that, when counted individually, the directories still appear take up the full space:
$ du -sh orig_1
149M orig_1
This is because du keeps track of files it's already seen, and avoids counting them twice.
--link-dest takes a path relative to the destination. You want --link-dest=../orig.
Standard Unix filesystems do not allow hard links to directories, except for the special . and .. links. --link-dest only creates hard links for files, the rest of the directory structure is recreated as real directories.
And even if hard links were allowed to directories, du would still show the full size of each link. When using hard links, there's no distinction between the original and the link, they're each just names that refer to a particular inode, and du would scan them equivalently.