Re: Lost+Found directory (was: self image)

In message [ref] you wrote:

quoted

Your new filesystem is twice as big as the old one, so it  will  have
more inode blocks etc. Also, you may notice that our filesystem image
does not contain the (rather large) lost+found firectory.

How come the lost+found directory is large, or even has a single entry
to begin with? I thought it was used by fsck to collect file data lost
due to file system corruption over time; so in a freshly built embedded
image, there shouldn't be any of that. Did I miss something?

When the filesystem is created (by mke2fs) special care is  taken  to
create a big directory that allows for many entries to be reconnected
without  need  to  grow  the directory which could be dangerous on an
already corrupted filesystem. Have a look:

	# ls -l
	total 12
	drwx------    2 root     root        12288 Dec 11 10:14 lost+found
	# df .
	Filesystem           1K-blocks      Used Available Use% Mounted on
	/tmp/rd                  63461        13     63448   1% /mnt/tmp
	# rmdir lost+found/
	# df .
	Filesystem           1K-blocks      Used Available Use% Mounted on
	/tmp/rd                  63461         1     63460   1% /mnt/tmp

As you can see the "lost+found"  as  created  by  the  "mke2fs"  tool
occupies 12kB of filesystem space which get freed when you remove the
directory.

	# mkdir lost+found
	# ls -l
	total 1
	drwxr-xr-x    2 root     root         1024 Dec 11 10:15 lost+found
	# df .
	Filesystem           1K-blocks      Used Available Use% Mounted on
	/tmp/rd                  63461         2     63459   1% /mnt/tmp

If you manually create a directory it will occupy only 1 kB instead.

In older times you used to run something like
	for i in 0 1 2 3 4 5 6 7 8 9 ; do
	  for j in 0 1 2 3 4 5 6 7 8 9 ; do
	    for k in 0 1 2 3 4 5 6 7 8 9 ; do
	      touch lost+found/${i}${j}${k}
	done ; done ; done
	rm -f lost+found/*

to "blow up" the lost+found/ directory to allow  for  a  sufficiently
large   number   of   directory   entries.  Today  mke2fs  does  this
automagically (and people forget why it needs to be done).

Best regards,

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd@denx.de
Why can you only have two doors on a chicken coop? If it had four  it
would be a chicken sedan.

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