People seem to know how to get information about me.  How do I get
information about them?  And how do I change some of my
personal information if I need to.

22 responses total.

This response has been erased.

Of course, if you don't want to be able to read the information about
yourself, you can do    !chmod 000 .plan     ... but you also won't be
able to change it unless you chmod it back to something reasonable.

The finger command will say "no plan" if the person you finger has
no .plan file or if the file exists but you have no right to read it.
Each of the three digits you give gives someone rights.  The first gives
the file's owner's rights.  The second gives rights for the group associated
with the file.  (For files created by ordinary users on Grex, this is
normally all other users.)  The third digit gives the rights everyone
except the owner & the group has to the file.

The meaning of each digit is basically:
7 - read, write, & execute access
6 - read & write access
5 - read & execute access
4 - read access only
3 - write & execute access (you mean you let them write to the file
       but not read it? And they can't execute without reading!)
2 - write access only (again, why bother?)
1 - execute access only (basically meaningless without read access)
0 - no access

For normal files, execute access only gives someone the right to run the
thing - so it should be a program or shell script.

If it's a directory, execute access allows someone to use the directory as
part of a path to get to a file; read access allows someone to see what
files are in the directory; and write access allows someone to create &
delete files in the dir & things like that.

This is all slightly oversimplified, but that's the basics.  And as it's
a whole lot more than you asked, I'll shut up.
(for more, do   !man chmod)

If you're like me, and don't like to remember thos numbers, you can also
do it with letters.  For example, if I have a file that I don't want the
group that owns the file, or others, to be able to read, write, or
execute, the file, I can do:

chmod og-wrx filename

If I do want to let them read and execute the file, I can type:

chmod og+rx filename

Thank you one and all. 
But if I may impose one more question...
Y'all refered to a group.  May I ask what that's all about.
I know it's a stupid question but...

Not a stupid question at all.  A "group" is a group of
people (big surprise, huh?) defined by the system for some
reason.  I.e. the group "members" consists of only people
who are Grex members, "lynxadmin" only has those people
who are allowed to modfy the Lynx system files, etc.
If you want tosee a listing of the various groups and
who's in them, try this at the Respond or Pass? prompt:

        !more /etc/group

Every file has a group defined for it, as well as an
owner.  If you or I create a file, it will be defined
with us as the owner and "people" as  (everyone) as the
group.  It's possible to change the group, and then permit
access to the group members without giving access to everyone.
For instance, the Lynx system files are given group
lynxadmin and permitted 775, so the file's owner can read, write,
and execute the files; the other people in the lynxadmin
group can read, write, and execute the files; and everyone
else can read and execute the files, but not write to them.

For most users, though, there's really no difference
between "group" and "other".

If you look at your files by doing    !ls -al    you'll see the permissions
(in a form showing r=read w=write x=execute -=none) for owner/group/other,
and the owner, & the group (plus other stuff).  The group on your files
is probably   people  - same as mine & (I think) everyone else's.  On Unix
systems supporting other types of activities than we do here, the group
is heavily used for access control - people working together on something
are put in a group.  Here, most everyone's default group is the same,
everyone is in it, & so the "everyone-else" access rarely gets considered
when it comes to user files.

What exactly (technically) does chmod do? I figures it was short for
change mode? What all can you do with that command? For instance,
one question I have had about chmod is, I know it can be used to make
ftp directories accessable to other people. But, can you do, say,

chmod g+w www dave1?

And make my directory /www accessible only to dave and myself?
Becasue I have some hidden directories at a differant freenet and I don't
want them open for everybody. Just certain people.

Every Unix file has an individual owner (the user who "owns" it), and a
group owner (the group it belongs to, where the group has to be one of
the system-recognized groups listed in /etc/group).

A Unix file has 3 sets of permissions:

  (1) what the owner can do with it (read, write, execute).
  (2) what the group it belongs to can do with it (same).
  (3) what everybody else can do with it (same).

The chmod command can be used to change these permissions.  But you
can't change anything but owner's permissions, group's permissions,
and other's permissions, because these are the only classes of
permissions that Unix supports.

In particular, you can't permit a file to just yourself and one other
selected person.

And, for what it's worth, unless you're root you can't chmod anyone's
files but those *you* own.

James,   chmod g+w www davel   would give write permission to the group
associated with two files - www and davel - for those files.  On grex,
the group would normally be "people", i.e. all the normal users on the
system. The arguments to chmod are 1 list of permission assignments
(various formats accepted for that list), and an arbitrarily-long list
of files whose access modes are to be changed.

Hmmm, thats interesting. So, can I chmod 644 a whole directory?
I accidently left a directory open somewhere and anybody can edit my homepage.
I can't let that happen for too much longer.

Directories should be permitted 7xy: the system must "execute" them. 711
would permit persons to read (permitted) files in the directory if they
knew the filename, but not read the directory. 

Re #10:  Leaving a directory open doesn't mean that anybody can edit
the files in it.  The individual files would have to be write-permitted
to others for that to happen.

They are...

The perms on a directory mean something slightly different than those
on a normal file (as most people think of it, anyway).  Read access lets
someone see what files are in the dir; write lets someone add or delete
files in the dir; and execute access lets someone use the dir as part
of a path to a file.  And as John pointed out, the files in the dir have
their own permissions (but having read permission on a file in a dir you
don't have execute access to may not help you much).

If I'm reading /etc/group right, people is a group that looks like a list
of most of the staff, rather than everybody on Grex.

Hmm.  You seem to be right - but it's an out of date staff list, not
a current one (presumably that is why partial).

<tries to remove foot from mouth>

Actually, group 'people' includes just about everybody on Grex.
Every group has a GID (group id number) as well as a possible name.
The GID of group 'people' is 50.  Another way to be a member of
a group, besides being listed in the /etc/group file, is to have
the GID of the group in the 'group' field of the account file
/etc/passwd.  As a look at /etc/passwd will show, users are
assigned GID 50 in the group field by default.

This response has been erased.

Learn something every day.  I knew about the group field in /etc/passwd; just
didn't know that conferred group membership.  (This is, however, what controls
the group that goes on the files you create, by default).

I would be grateful for advice in making the following permission change 
in my file list:

    -rw-r--r--   1 rksjr    entities      237 Oct  8 14:45 m03.oct.08     

I am seeking to change the aforementioned permission sequence to:

    -rw-------   1 rksjr    entities      237 Oct  8 14:45 m03.oct.08     

My failed attempts to make the change are as follows:

> chmod mask 600 ./m03.oct.08
chmod: invalid mode
>
> chmod permission 600 ./m03.oct.08
chmod: invalid mode
>
> chmod new 600 ./m03.oct.08
chmod: invalid mode
>

chmod 600 ./m03.oct.08

(Try "man 1 chmod" for the chmod manual page.)

Re: #21: "chmod 600 ./m03.oct.08" works. Thank you!

Response not possible - You must register and login before posting.

- Backtalk version 1.3.30 - Copyright 1996-2006, Jan Wolter and Steve Weiss