Home directory files invisible!

suvayu ali fatkasuvayu+linux at gmail.com
Fri Apr 23 19:20:25 UTC 2010


Hi,

On 23 April 2010 08:52, Chris Adams <cmadams at hiwaay.net> wrote:
> 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.
>

After reading your response I knew more precisely what to look for and
after some searching and looking @ `info coreutils "File permissions"
"Mode Structure", I think I understand them now.

However I failed to find how to see whether any of those bits are set
for a file. I tried `ls -l ' in /bin, /usr/bin, and /tmp but didn't
notice anything obvious. I also failed to find any appropriate option
for ls to list it either. Am I looking in the wrong place?

Also in what situations would seting the setuid or setgid bits help? I
could think of some, like writing configuration files for the
application which are otherwise owned by someone else, maybe for a web
server or a daemon or maybe some automated backup solution. Are these
valid scenarios?

> 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>

-- 
Suvayu

Open source is the future. It sets us free.


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