yellowdog-newbie Digest, Vol 32, Issue 19
Derick Centeno
aguilarojo at verizon.net
Tue Apr 24 17:09:54 MDT 2007
Hi Thomas:
For the sake of clarity I'll address your questions separately.
First the question which ends "...as root and proceed... as a tutorial?
The phrasing of your question implies a confusion which I'd like to
highlight.
If you are using Linux on your own computer or on a public or library or
lab computer there would be some difference in the ideas which follow
but not much. For the sake of brevity, I'll mention them in passing --
leaving you to inform me if you require more details.
Every Linux distribution could do a better job in clarifying the
information which follows but it appears rather difficult to keep this
kind of information available in a reliable manner to users. The
beginning should always be a clarification regarding what is root, and
accessing the functions of root via the superuser and sudo commands.
Frankly, the reason most distributions and even universities such as
Duke, sadly do this so poorly is that they are relying on users and
students to refer to tomes on Linux System Administration either in
their libraries or on the net which discuss these commands.
Fortunately, there are legions of books on Linux Sys. Admin. so it
should be no problem to find one which makes sense to you (via the
library first) and then purchase it for your future and continuing
reference; these works will discuss the details of root, superuser and
sudo appropriately.
Root is relegated to system level control. The password for root should
be unique to that level of activity alone -- one is adding a new printer
to the system, a new user, one is removing a user, one is modifying or
restricting access a user has to certain system functions or perhaps
only certain applications within a system. Other system administrator
functions would be adding a new hard disk, erasing a hard disk or making
other modifications to that disk, moving and erasing files, correcting
and writing code and so on. There is a distinction usually between
system admin. function and programmers; the sys. admin. responsibilities
are attention to system resources on or within a computer while the
programmer is concerned with accessing and utilizing those resources.
You may be just one person, but you are doing two different tasks or
functions when behaving as a programmer or a system administrator as far
as Linux or Unix is concerned.
It is a good idea to reference (and have a very clear idea) what you
intend to do first, before you do or execute it.
The superuser or su command utilizes and requires the same password as
root and functions fully the same as root. The distinction between them
is rather of historical interest, rather than functional. The sudo
command however is different, it requires the use of the user's password
- not the system administrator's. Also it limits access to system
resources to a certain defined period which can be modified by the
system administrator. Your expressed concern regarding mucking with
your system is exactly what sudo is for -- to limit your capacity for
damage. The idea with sudo is to limit what you are doing so that you
are restricted to doing one thing only at one time as system
administrator when time is up, that's it -- you are dropped immediately
back into user mode without you having to log back into it. The user
mode is restricted to using applications like Open Office or the Gimp or
xine or playing games, etc.
When however you are in su mode you need to remember to exit that mode.
Ok?
Now as regards to yum. One can use yum via root, su or sudo. Given
your current confusion it may be to your advantage to use sudo nearly
exclusively. However there is a procedure involved to register with the
particular Linux or Unix system first so that you are recognized by it,
as a user of sudo. The system administrator can access the details
regarding those procedures for that machine you are using or intend to
use. Now if we are talking about a machine you own, then you are the
system administrator and you need to learn how to register that user
name -- say, lightsaber -- into a user's list which the sudo command
which then will cross check for legitmacy before granting you access.
Essentially this means you have to register lightsaber, as a user the
sudo command will recognize correctly into a database which the sudo
command will nearly instantaneously reference when that command is invoked.
Once that is done, then sudo can be used on that machine. If you intend
to use sudo on another machine, you will have to be registered by the
system administrator of that machine to use sudo there.
The above is not an explanation on how to use sudo, but merely a
discussion of the procedure required to make sudo useful.
Assuming the registration of lightsaber has been done. Lightsaber would
be a registered user known to that Linux system with a unique password
and would also be registered within the database which sudo would
reference. This being completed then one could do the following:
$sudo yum search "*xine*"
password:
Let me detail what is going on at this point. One is within a user
shell, meaning that one is within the one of the shells (here ksh) which
the system administrator has determined that a user is allowed to use on
this system. Invoking sudo allows the immediate use of any system admin
level command -- including yum. The password expected is lightsaber's
password; after that yum will be executed. After yum finds and does
it's listing -- then lightsaber will be returned to the same user prompt
he left.
Remember as su, one has to login as su, then invoke yum, then logout.
Then one has to login as a user.
All the above was a prelude discussing more how to use a Linux system
effectively protecting both it and yourself from the human tendency to
have a "Homer Simpson" moment -- "Hmmm... what would happen if I use
this funny looking command ---"
I'll address the question regarding yum along with your other questions
you sent about yum, ok?
Best wishes... Derick.
Thomas Kutz wrote:
> Thank you Derick. The URL's provided are an excellent reference.
> If someone had never seen yum would they login to their own
> machine as root and proceed to type yum with the various options
> listed as a tutorial? When the website says "point to the correct
> server" what does that mean in English? How does one begin to
> use yum?
>
> that's my confusion. If I know the context I can apply the
> examples otherwise I end up with a vast amount of statistics and
> other information concerning applications installed in my PS3. At
> the root prompt I typed:
>
> # yum info <return>
>
> and got so many screens I gave up after about a thousand lines of
> inventory of programs.
>
> Where do I start if I want to upgrade from ver. 1127 to ver. 1208
> of YellowDog?
>
> Thomas Kutz
>
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> 1. I want to update my PS3 from 1127 to 1208 w. yum -- how?
> (Thomas Kutz)
> 2. Re: I want to update my PS3 from 1127 to 1208 w. yum -- how?
> (Derick Centeno)
> From: Thomas Kutz <thomas2kutz at yahoo.com>
> To: yellowdog-newbie at lists.terrasoftsolutions.com
> Date: Thu, 19 Apr 2007 12:32:50 -0700 (PDT)
> Subject: I want to update my PS3 from 1127 to 1208 w. yum -- how?
>
> I am lost trying to find out how to use yum at all. Do I create
> /etc/yum files on my PS3? There are 3 example files
> yellow-dog-bas.repo, yellow-dog-extras.repo, yellow-dog-updates.repo.
> Are these templates to be modified on
> my machine and invoked by commands there?
>
> The section mentions "Pointing yum to YDL.net <http://ydl.net/>" . Where and how
> does this "pointing" take place?
>
> I need a place to start. When I looked at http://linux.duke.edu/projects/yum
> I could not find anything that did not assume I already
> knew.
> thanks in advance for your help,
> Thomas
> Kutz
>
> ------------------------------------------------------------------------
> Ahhh...imagining that irresistible "new car" smell?
> Check out new cars at Yahoo! Autos.
> <http://us.rd.yahoo.com/evt=48245/*http://autos.yahoo.com/new_cars.html;_ylc=X3oDMTE1YW1jcXJ2BF9TAzk3MTA3MDc2BHNlYwNtYWlsdGFncwRzbGsDbmV3LWNhcnM->
> From: Derick Centeno <aguilarojo at verizon.net>
> To: Discussion List for New Yellow Dog Linux Users
> <yellowdog-newbie at lists.terrasoftsolutions.com>
> Date: Fri, 20 Apr 2007 03:39:27 -0400
> Subject: Re: I want to update my PS3 from 1127 to 1208 w. yum -- how?
>
> Hi Thomas:
>
> Here is the place to start regarding yum:
>
> http://www.terrasoftsolutions.com/support/solutions/ydl_5.0/yum.shtml
>
> The information on this page has been modified to address YDL 5
> for the PS3.
> Other information for the PS3 which could be useful to you is
> available
> here:
>
> http://www.terrasoftsolutions.com/support/solutions/ydl_5.0/
>
> Good Luck...
>
> Thomas Kutz wrote:
> > I am lost trying to find out how to use yum at all. Do I create
> > /etc/yum files on my PS3? There are 3 example files
> > yellow-dog-bas.repo, yellow-dog-extras.repo,
> yellow-dog-updates.repo.
> > Are these templates to be modified on
> > my machine and invoked by commands there?
> >
> > The section mentions "Pointing yum to YDL.net " . Where and how
> > does this "pointing" take place?
> >
> > I need a place to start. When I looked at
> http://linux.duke.edu/projects/yum
> > I could not find anything that did not assume I already
> > knew.
> > thanks in advance for your help,
> > Thomas
> > Kutz
> >
> >
> ------------------------------------------------------------------------
> > Ahhh...imagining that irresistible "new car" smell?
> > Check out new cars at Yahoo! Autos.
> >
> >
> >
> ------------------------------------------------------------------------
> >
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> Ahhh...imagining that irresistible "new car" smell?
> Check out new cars at Yahoo! Autos.
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