[Cialug] Very well-hidden directory

[Daniel A. Ramaley]

There exists a hidden directory on a machine, one so hidden that not 
even "ls -a" can show it. How is this possible? This is on Oracle Linux.

# ls -a /u02/app/oracle/oradata/datastore
.  ..  DVLP  TREL  lost+found
# ls -a /u02/app/oracle/oradata/datastore/.ACFS
.  ..  .fileid  repl  snaps

Note the lack of a ".ACFS" directory in the first "ls" command above, but that it seems to exist if i specify the full path to it in the second "ls"!

"df" shows that both are the same filesystem:

# df -h /u02/app/oracle/oradata/datastore/{,.ACFS}
Filesystem            Size  Used Avail Use% Mounted on
/dev/asm/datastore-495
                      1.7T  302G  1.4T  18% /u02/app/oracle/oradata/datastore
/dev/asm/datastore-495
                      1.7T  302G  1.4T  18% /u02/app/oracle/oradata/datastore

"du" is a bit more interesting:

# du -hs /u02/app/oracle/oradata/datastore/{,.ACFS}
141G	/u02/app/oracle/oradata/datastore/
293G	/u02/app/oracle/oradata/datastore/.ACFS

I'm not trying to solve any particular problem other than a bit of ignorance on my part. I didn't think it was possible to hide a directory so well that common tools like "ls" and "du" can't see it. Tab completion in bash also doesn't work for discovering the directory; i have to explicitly type out all the characters in its name to interact with it.

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Daniel A. Ramaley  |  Network Engineer 2
Drake Technology Services (DTS) | Drake University

T: +1 515 271-4540
F: +1 515 271-1938
E: daniel.ramaley at drake.edu