[plug] To Anthony J. Breeds-Turima - file permissions

[James Elliott]

Hi Tony

Thank you for an excellent answer to my question.

James Elliott

----- Original Message -----
From: "Anthony J. Breeds-Taurima" <tony at cantech.net.au>
To: <plug at plug.linux.org.au>
Sent: Tuesday, May 07, 2002 12:29 PM
Subject: Re: [plug] file permissions


> On Tue, 7 May 2002, James Elliott wrote:
>
> > File permissions are typically read, write, and execute (rwx), but
> > sometimes you see and "S" or  "t" when you do and ls -l ... what do
these
> > mean, please, and are there any other permissions?
>
> an ls -l will show you 10 possible permissions fields
> ie
> ?rwxrw---x
> The first field is usually a '-' BUT you will see it as 'd' for
directories
> and 'l' for soft links.
>
> Owner permissions
> 'r' File is readable by owner
> 'w' File is writable by owner
> 'x' File is executable by owner
> 's' Means it has the execute bit AND the setUID bit set.
> 'S' Means it doesn't have the execute bit BUT the setUID bit is set.
>
> Group Permissions
> 'r' File is readable by group
> 'w' File is writable by group
> 'x' File is executable by group
> 's' Means it has the execute bit AND the setGID bit set.
> 'S' Means it doesn't have the execute bit BUT the setUID bit is set.
>
> Group Permissions
> 'r' File is readable by everyone NOT covered by owner or group
> 'w' File is writable by everyone NOT covered by owner or group
> 'x' File is executable by everyone NOT covered by owner or group
> 't' Means it has the execute bit AND the sticky bit set.
> 'T' Means it doesn't have the execute bit BUT the sticky bit is set.
>
> setUID means that the file (executable) will run as the actual owner NOT
> the user running the command.  This is used in apps like:
> /bin/su
> /bin/ping
> /bin/mount
> /bin/umount
>
> setGID has a similar meaning to setUID but as you'd prolly expect it
affect
> the groupID not the userID on a Redhat 6.2 system /sbin/netreport has
setgid
> set.
>
> The sticky bit is somewhat unused now days.  It basically meant leave this
> executable in memory even when it isn't running.  It was used for apps
that
> were frequently run as a way to boost performance.
>
> Each of the setuid, setgid and sticky bits have slightly different
meanings
> on directories, but you asked about files :)
>
> Yours Tony.
>
> /*
>  * "The significant problems we face cannot be solved at the
>  * same level of thinking we were at when we created them."
>  * --Albert Einstein
>  */
>
>