Shouldn't a file I create default to being owned by me?

[Yuki Cuss]

Dave M G wrote:

> Ubuntu Users,
>
>    I have Appache, PHP, and MySQL all set up and running smoothly. I 
> also have three different web sites that I keep in my localhost 
> directory and view from within FireFox, without any problems.
>
>    So, I was suprised when I created a little PHP script to test 
> something, and when I viewed it through FireFox, it said there was a 
> "permissions error".
>
>    At first I thought this must be a PHP problem, because I create and 
> view files within my localhost directory all the time. But the people 
> on the PHP mailing list were sure it was just a file permissions problem.
>
>    Sure enough, I looked at the file properties from a command prompt, 
> and the default was not to be read or written to:
> -rw-------  1 dave dave 20 2006-02-13 22:45 
> /home/dave/web_sites/phpinfo.php
>
>    So I changed the properties with chmod 777 and the file opens fine.
>
>    Now I'm confused by this. Why would this file, which I created and 
> saved using gedit, automatically have its permissions set up so I 
> can't view or edit it? Why does no other file that I have made or 
> edited behaved like this? Is this a one time problem, or is there a 
> fundamental problem I'm missing?
>
>    Any advice would be much appreciated.
>
> -- 
> Dave M G
>
Perhaps you misread it;

-rw-------  1 dave dave 20 2006-02-13 22:45 
/home/dave/web_sites/phpinfo.php
That means *only* dave can view it. For a few more examples; from my 
filesystem:

drwx------    4 celtic celtic   4096 2006-02-17 18:47 .gconf
That means *only* celtic (myself!) can read/write/execute (ie. go into) 
that directory. (note the `d')

-rw-r-----    1 celtic celtic      0 2006-01-21 15:45 .gksu.lock
This means that only I (celtic) can read/write to this file, and members 
of the group `celtic' (eg. myself, by default) may read it.

drwxr-x---   19 celtic celtic   4096 2006-02-17 22:01 code
Much the same, except both I and group members of `celtic' can 
read/execute the directory.

drwxr-xr-x    3 celtic celtic 4096 2006-01-28 20:25 vmware
Now, I can read/write/execute, members of `celtic' can read/execute, 
*and* all other users can read/execute.

Files by default are created with the permissions 666 MINUS your umask. 
Directories are 777 MINUS your umask. To find your current umask, try 
typing it at a console; the default is 0022.

celtic at xyrias:~$ umask
0022
celtic at xyrias:~$

That means, if I create a directory, its permissions will be 777-22 = 
755. If you don't know how permissions are read in octal, here's the 
break down;

1 represents `x' (executable); 2 represents `w' (writable), and 4 
represents `r' (readable). Read the digits in left to right order; user, 
group, other. Thus, 755 means that the `user' (owner, eg. dave, celtic) 
can read+write+execute (1+2+4=7). The group members (celtic, dave, 
wheel, what have you ..) can read+execute (1+4=5), as can the other 
users (everyone else).

The most likely thing that happened is that your umask is set to 0077. 
(note that you can read a umask just like a normal permission, except 
that you're *denying* the privileges). Ignoring the first digit, which 
is for special bits, you can see that you deny the user (dave) nothing; 
but, deny group and the rest of the world everything.

Check your umask often, and read your permissions right. Don't set files 
to chmod 777 because it's unnecessary; 755 is good for scripts, 644 for 
files, 600 for private files; 640 for files you want your group to see; 
660 for files you want your group to write!

It's pretty trivial when you look at it!

 - Yuki.
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