Re: IFS Permissions

"I think you've misread it. The setgid bit *is* a Unix/Linux thing.”

Fair enough - I see now that I misread the first part of Scott’s email. It does makes me wonder why supposed Unix/Linux experts failed to recognize what the value represented - and that apparently includes the developers of the Wordpress plugin that is signalling the problem. But that is a different matter.

I’m aware of it being an octal representation.

Turning it off would probably be safe enough and I may try it to see if that cures the problem we have with WP not being able to automatically update files. Just as an experiment we literally copied our entire setup to a Linux box and the auto update works there. On our system it fails because it determines that the temporary directory does not contain any files - it does.

Thanks to all for their help.


Jon Paris

www.partner400.com
www.SystemiDeveloper.com

On Jun 26, 2015, at 12:12 PM, John Yeung <gallium.arsenide@xxxxxxxxx> wrote:

On Fri, Jun 26, 2015 at 10:59 AM, Jon Paris <jon.paris@xxxxxxxxxxxxxx> wrote:

Thanks Scott - as ever the perfect description. So I guess this has no equivalent in Unix/Linux systems.

I think you've misread it. The setgid bit *is* a Unix/Linux thing.

As I noted in another post, sadly it means that permissions are not the cause of our issues with Wordpress and we need to look elsewhere.

My takeaway from Scott's explanation is that you basically have a
couple avenues:

1. You can adjust the permissions on the relevant directories, so that
they are 755 instead of 2755. To do this, use

chmod g-s mydir

2. You can try to fix the plugin (or whatever program is detecting the
permissions) so that it ignores high-order bits (so just chop off the
leading '2' and ignore it).

In case you're not aware, the digits are just an octal representation
for permission bits. The rightmost 9 bits (3 octal digits) determine
the access rights. From a purely "can I read it? can I write it? can I
execute it?" standpoint, 2755 is IDENTICAL to 755. It's just that for
directories, the setgid bit has a special meaning when creating new
objects within that directory. So when people say "it should have no
effect" what they mean is "the RELEVANT bits are identical, and other
bits OUGHT TO BE ignored (but maybe some software is mistakenly not
ignoring it)".

We have no way to know, based on the information you've given us,
whether turning off the setgid bit (or ignoring it) is safe. It could
be that you have software which depends on that setgid bit being a
particular value (because it's going to create objects in the affected
directory or directories).

John Y.
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