[Cialug] Very well-hidden directory

[Daniel A. Ramaley]

Thanks for the responses, everyone.

"acfs" seems to be an Oracle-specific filesystem, and .ACFS is where it 
keeps information related to snapshots and replication. The acfs 
filesystem type is where the Oracle database is stored. I'm not 
surprised that they have a custom filesystem for the database.

On 2015-05-26 at 10:16:36 Josh More wrote:
> I don't know if this is how Oracle handles .ACFS specifically, but you
> can create this behavior by creating a directory, accessing that
> directory in a process so it's "open", then deleting the directory.
> 
> The files will still be there as the "unlink" operation is pending
> until the process closes out.  However, the filesystem access will be
> by name only and won't show up via ls or tab completion (which is
> really the same operation).
> 
> -Josh
> 
> On Tue, May 26, 2015 at 10:13 AM, Jeffrey Ollie <jeff at ocjtech.us> 
wrote:
> > "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
> >> 
> >> _______________________________________________
> >> Cialug mailing list
> >> Cialug at cialug.org
> >> http://cialug.org/mailman/listinfo/cialug
> > 
> > --
> > Jeff Ollie
> > _______________________________________________
> > Cialug mailing list
> > Cialug at cialug.org
> > http://cialug.org/mailman/listinfo/cialug
> 
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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