umask not working?

[Ken Brown]

On 3/21/2018 6:36 AM, David Allsopp wrote:
> Ken Brown
>> On 3/19/2018 8:48 AM, David Allsopp wrote:
>>> Is this expected behaviour:
>>>
>>> OPAM+DRA@OPAM ~
>>> $ uname -a ; umask ; touch /tmp/foo ; ls -l /tmp/foo ; mkdir /tmp/bar
>>> ; touch /tmp/bar/foo ; ls -l /tmp/bar/foo CYGWIN_NT-6.1-WOW OPAM
>>> 2.10.0(0.325/5/3) 2018-02-02 15:21 i686 Cygwin
>>> 0022
>>> -rw-r--r-- 1 OPAM+DRA OPAM+None 0 Mar 19 13:44 /tmp/foo
>>> -rw-rw-r--+ 1 OPAM+DRA OPAM+None 0 Mar 19 13:44 /tmp/bar/foo
>>>
>>> Why does the file /tmp/bar/foo get g+w when /tmp/foo doesn't - I'm not
>>> sure what to look at on my system to diagnose what I may have
>>> inadvertently tweaked. The directory itself is:
>>>
>>> drwxr-xr-x+ 1 OPAM+DRA OPAM+None 0 Mar 19 13:44 /tmp/bar
>>
>> See if this helps:
>>
>>     https://cygwin.com/faq/faq.html#faq.using.same-with-permissions
> 
> Thanks for the pointer. I wonder from it if this could be to do with the Cygwin installation being old (but upgraded). I tried on the same machine creating another installation to C:\cygwin2 (which behaves as Roger Wells noted) and then ran getfacl /tmp on each:
> 
> Old installation:
> 
> # file: /tmp
> # owner: OPAM+DRA-Admin
> # group: OPAM+None
> user::rwx
> user:OPAM+DRA:rwx
> group::r-x
> mask:rwx
> other:r-x
> default:user::rwx
> default:user:OPAM+DRA:rwx
> default:group::r-x
> default:mask:rwx
> default:other:r-x
> 
> Fresh installation:
> 
> # file: /tmp
> # owner: OPAM+DRA-Admin
> # group: OPAM+None
> # flags: --t
> user::rwx
> group::rwx
> other:rwx
> default:user::rwx
> default:group::r-x
> default:other:r-x
> 
> I expect that the extra OPAM+DRA:rwx on the old installation was manually added by me, years ago. What are the "mask" entries all about?
> 
> The default:mask entry seems to be the crucial one, as if I do setfacl default:mask:rwx /tmp on the fresh installation, then I get the same behaviour as on the old installation.
> 
> However, I'm struggling to find references for either what these mask entries are, or how they ever appeared?

If you search the web for "Posix acl mask" you'll find lots of 
information.  Here's one that seems pretty good:

   https://cs.unc.edu/help-article/posix-acls-in-linux/

Ken


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