thorny (for me) permissions problem

[Jeremy Chadwick]

On Tue, Oct 07, 2008 at 10:23:53AM -0400, John Almberg wrote:
>
> On Oct 7, 2008, at 9:34 AM, Jeremy Hooks wrote:
>
>>>> 4. however, after upload, the file has the ownership A:B (i.e,  
>>>> owned by
>> A, group B) with permissions -rw-r--r--. So B does not have permission 
>> to
>> delete the file.
>>        -rw-r--r-- 1 user_a user_b 154879 Oct 7 08:40 data_file.csv
>>
>> Hi John.
>>
>> Correct me if I am wrong but permission to delete a file depends on  
>> the
>> users permissions for the containing directory.  If B has write  
>> permission
>> on the directory then B can delete the file.  However you will likely 
>> need
>> to use 'rm -f'.
>
> Argh!!!!
>
> As a newbie admin, I really have a tough time with permissions. I swear I 
> got a permissions error when I tried to delete this dang file, but I just 
> logged in as B and was able to delete it just fine. Of course this is 
> because B owns the directory.
>
> I guess I must have done something boneheaded an hour or two ago...  
> gosh, I hate wasting time. Mine, and the lists, of course.
>
> Well, thanks to Valintin, I did figure out how to change the umask for 
> pure-ftpd. So now uploaded files have the permissions I wanted, even if 
> they are not needed.

Be careful with what you've done.  If you changed the umask on the ftpd
as a whole, then suddenly unrelated users are going to find their files
writeable by whatever group/GID they default to.

For example, on my systems, everyone's default group is "users", and I
definitely would not want group-write set to files people upload on
their accounts!  The idea of a user being able to edit or zero out other
users' data is not good.

But that's also what the underlying directory permissions are for...  As
you've learned/remembered today.  :-)

> And thanks to the rest, I figured out it was working all along... And  
> now I can't even duplicate the error I saw before...
>
> <sigh> Does this ever get any easier??? How can any one person remember 
> all this stuff???

It gets easier with time; don't rush yourself.  :-)  Even those of us
who have been using UNIX for almost 20 years forget the simplest of
things on a regular basis.

Be sure to let us know when you make the infamous "rm -fr" typo that
nukes either / or ~.  :-)

-- 
| Jeremy Chadwick                                jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |