question about Ext2/3 append-only attributes

question about Ext2/3 append-only attributes

[Xin Zhao]

I read some specification says that if append-only is set to a
directory, you can only create or modify files in that directory, but
no delete.

But when I tried this attribute on a directory,  I was not able to
create new files in that directory.  let's say the derectory is /dev, 
I set it to be append-only with:

chattr +a /dev.

Then I cannot create new files in it with command cp /dev/aa /dev/bb,
not that aa is a normal text file here.

Why the result conflict with the specification? Is there anyway to
make a directory really append-only? Thanks in advance!

-x

Re: question about Ext2/3 append-only attributes

[Valdis.Kletnieks]

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On Tue, 03 May 2005 16:58:13 EDT, Xin Zhao said:
> I read some specification says that if append-only is set to a
> directory, you can only create or modify files in that directory, but
> no delete.

Could you be more specific on "some specification", and convince us that
what you read wasn't in fact wrong about things?

> But when I tried this attribute on a directory,  I was not able to
> create new files in that directory.  let's say the derectory is /dev, 
> I set it to be append-only with:

Well, creating a new file implies creating a new entry in the directory
pointing at the inode, which is "appending" to the directory.  So this
isn't at all surprising, and I'd consider the spec that says "create or modify"
to be broken.

Were you possibly thinking of the +t (sticky) bit on a directory, which when
set restricts who can unlink the file?


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Re: question about Ext2/3 append-only attributes

[Robert Love]

On Tue, 2005-05-03 at 16:58 -0400, Xin Zhao wrote:

> I read some specification says that if append-only is set to a
> directory, you can only create or modify files in that directory, but
> no delete.

I suspect that your interpretation of the specification is wrong.

+a says that files can only be opened in append mode--O_APPEND.  It is
very specific as to what it allows.

Perhaps you want the sticky bit, +t, set on the directory?

	Robert Love