Re: I'm stubborn or stupid (and that's not xor) (Was: CVS Import Permissions)

Duane Whitty <duane@xxxxxxxxxxxxxx> · Tue, 31 Jan 2006 06:29:35 +0000

Giorgos Keramidas wrote:

On 2006-01-31 00:44, Duane <duane@xxxxxxxxxxxxxx> wrote:
Hi everyone,
On the CVS server machine should our CVS repository directory belong to
the cvs group, i.e. user==root, group==cvs?

It's usually a good idea.
And as for the umask, as it appears to be 027, if we give the
cvs group write permission on /usr/local/cvsrep then when we
import our projects they will be writeable by members of group
cvs and the owner of the project, in this case jim.

No.  This is not how `umask' works.  Whatever value `umask'
currently has is logically-AND-ed with 0666.  This means that by
using 027, the result is:
    $ python
    >>> print "%04o" % (066 & 027)
    0026
These are the bits that will be turned *off* for new files (see
the umask(2) manpage for details), so to find out which
permission bits are allowed, you have to use the reverse mask:
    >>> print "%04o" % (0777 & ~(066 & 027))
    0751
The 0751 allowed-bits mask is equivalent to:
    rwxr-x--x
This means that with a umask of 027, you are effectivelly
allowing only the bits in ``rwxr-x--x'' to be turned on by
default for new files, and this doesn't include write permission
for the group.
I know that the whole `umask' concept is a bit tricky to grasp,
since it depends on knowledge of numbering with an octal-base
*AND* it works in the reverse order of that people usually think
it does, but hopefully, with the help of our excellent manpages
and a bit of experimentation, it will become more obvious :)
I apologize if I am being all the things suggested in my
subject heading.

Nah!  Never apologize for a question.  There is no such thing as
a stupid question for this list (well, unless the question refers
to Windows, of course :P).
- Giorgos
______________________________________________

Thanks Giorgos.
That's an excellent explanation on 
computing the allowed bits.  One of my 
mistakes was logically-AND-ing with 0777.
Sincerely
--Duane
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Re: I'm stubborn or stupid (and that's not xor) (Was: CVS Import Permissions)

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