Home directory files invisible!

Chris Adams cmadams at hiwaay.net
Fri Apr 23 15:52:08 UTC 2010


Once upon a time, Suvayu Ali <fatkasuvayu+linux at gmail.com> said:
> I have never properly understood the leading bit in permissions. (the 0 
> in the 0755) Could you point me to some easily understandable resource?

The leading 3 bits is essentially an add-on to each of the user, group,
and other sections.  For user and group, the corresponding bit is the
set-id bit.  For executable filess with the set-user-id bit (e.g. 4xxx)
or set-group-id bit (e.g. 2xxx) set, the executable runs as the files
owner or group, not the calling user or group.

For directories, set-group-id means that new entries in that directory
inherit the group from the directory instead of the calling group.

The bit corresponding to other (e.g. 1xxx) is called the "sticky" bit.
On directories (such as /tmp), it means that only users/groups with
permissions to a file can delete it.

In old Unix, the sticky bit on an executable changed the way the kernel
paged it into and out of RAM, but I don't believe Linux uses it.
-- 
Chris Adams <cmadams at hiwaay.net>
Systems and Network Administrator - HiWAAY Internet Services
I don't speak for anybody but myself - that's enough trouble.


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