[Cialug] Very well-hidden directory

[Jeffrey Ollie]

"Any user can access the snapshot directory by specifying the path
name. However, the .ACFS directory itself is hidden from directory
listings of the root of the file system. This prevents recursive
commands, such as rm -rf or acfsutil tag set -r, from the root of the
file system inadvertently operating on snapshot files."

http://docs.oracle.com/cd/E11882_01/server.112/e18951/asmfs_util010.htm#OSTMG94000
http://bfy.tw/12I

On Tue, May 26, 2015 at 10:04 AM, Daniel A. Ramaley
<daniel.ramaley at drake.edu> wrote:
> 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.
>
> __
> 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
>
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-- 
Jeff Ollie