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Re: Subject: UMASK 002 or 022?


On 27.06.2017 19:11, gwmfms6@openmailbox.org wrote:

> I'd like to know why giving the world (Other) read access is even under
> consideration. If user wants a file to have Other readability this
> should be on the user to set it, but it should not be the default.

That can be solved by excluding people from the directory the files are
in -- in order to access a file, all directories on the way there need
to have at least 'x' permission for the current user.

So, an umask of 022 and having each user in a single-member primary
group gives the user all options:

 - To make your home directory completely private, chmod it to 750 (the
group permissions don't matter really, because there is no one else in
the group).

 - To allow other users to pass through your home directory (e.g. the
webserver on the way to ~/public_html), chmod your home to 751.

 - To create a directory that a group of users may write to, use chgrp
and then set permissions to 2770 (or 2775, if others should also be able
to read).

The Debian installation used to ask whether home directories should be
private by default, IIRC that question still exists but is too low
priority to be shown outside of expert mode. You can use

    dpkg-reconfigure adduser

to set this up, then new user home directories will be created with 750

This method allows a one-time setup of desired behaviour, while the
umask would need to be set at every login, and if it weren't set up
correctly, this would lead to files having the wrong permission with no
warning -- that's why it's more robust to just create files as readable
for others and lock them out of the entire home directory.

> What is the justification that every user be able to read everyone
> else's documents?

That depends on your use case. At university, we generally left the home
directory open, and kept a separate ~/private directory with restrictive
permissions, because it allowed us to easily share non-private files by
just telling people to get them from our home directories.


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