Re: [LINUX_Newbies] Re: Twice the same program

On Wed, Jul 10, 2013 at 9:34 AM, highskywhy@yahoo.de
<highskywhy@yahoo.de> wrote:
>
>
>
> Good afternoon
> Mi Jul 10 15:46:14 2013
> Thank You for help.
>
> >
> > --- In LINUX_Newbies@yahoogroups.com
> > <mailto:LINUX_Newbies%40yahoogroups.com>, "C. Beck" <usabecker@...>
> wrote:
> > >
> > > On Wed, Jul 3, 2013 at 1:40 AM, highskywhy@... <highskywhy@...> wrote:
> > > > Good morning
> > > > as far as I as newbie
> > > > understood Linux
> > > > is it possible to install
> > > > twice
> > > > Firefox
> > > > or
> > > > Claws
> > > > or any other programme?
> > > >
<snip>
> *
> Can somebody explain it to me
> or is it very very difficult?
>

Whether or not it is very difficult depends entirely on you.
Basically, what your current level of understanding is for Linux, OS
operation, how easy it is for you to learn, etc. all contribute to
whether or not you will find it difficult. So it is hard to say.
But for the sake of learning, you might as well try to do it, right?

> Can somebody explain it to me

Maybe Paul will chime in to provide better information/reading
materials as it sounds like he has much more experince with this than
I do. I will try to explain what I know and think I understand since
I have some down time. The basic issue with just installing the same
thing twice in the same place is that the second install will
overwrite all of the files of the first. So to have two separate
installations, they need to be installed in two different places.
There are a few ways to do this:

1) If you are compiling / building your program from source code with
gcc, you can set the install location with the option
'--prefix=name/of/your/install/directory'. Below is a link where you
can read about gcc, which is collection of program compilers that you
can probably find in your distributions software collection as an easy
to install package (maybe).
<http://gcc.gnu.org/>
On the menu on the right, you can find the manual. You can also enter
"Linux compile program tutorial" or "Linux build program from source"
or similar into your favorite search engine to find plenty of
walkthrough examples (add the name of your distribution to your search
string for more specific instructions). I'll caution that you may not
want to play around with compiling random programs on your everyday
system as you learn - It can be easy to make a mess that way.

2) another way is to install your program in a chroot-ed directory - I
think "chroot" comes from "change root". It is a way to make any
process launched from a directory to see that directory as root (i.e.,
"/"). This is useful for aplication testing or multi user systems as
anything operating in a chrooted directory is locked out of the rest
of the system. chroot is part of GNU core utilities:
<http://www.gnu.org/software/coreutils/manual/coreutils.html#chroot-invocation>
the wikipedia article has some basic information, so you may want to
look there also. If you use Debian (and maybe Ubuntu), someone put up
a tutorial on the debian wiki that includes includes installation of
debootstrap:
<http://wiki.debian.org/chroot> <-when they say "building a 'chroot'
in that tutorial, they are actually talking about making a fairly
minimal working OS inside of the directory you want to set as a root.
This is a good place to play around with compiling. :)

3) You could also use dpkg to set an installation location of a .deb
package. I do not think APT or aptitude can do this, and I know
nothing about YUM or RPM. But there are three options in dpkg that
allow one to set / specify an install location that I have looked at
before ; '--admindir=dir', 'instdir=dir', and '--root=dir' (where
'dir' is you directory path I believe)

dpkg is a command line program to manage Debian packages, which are
also found in at least Linux Mint and Ubuntu...
<------dpkg manual page excerpt---->
--admindir=dir
Change default administrative directory, which contains
many files that give information about status of
installed or uninstalled packages, etc. (Defaults to
/var/lib/dpkg)
--instdir=dir
Change default installation directory which refers to the
directory where packages are to be installed. instdir is
also the directory passed to chroot(2) before running
package's installation scripts, which means that the
scripts see instdir as a root directory. (Defaults to /)

--root=dir
Changing root changes instdir to dir and admindir to
dir/var/lib/dpkg.

<--end excerpt--->

The above makes me think that it you use '--root=dir' during an
install command and /dir/var/lib/dpkg exists because you previously
copied your libriaries there, you could install a different version of
a program without having dpkg destroy or bother the other program and
or its dependencies. But unless I am not understanding (and that is
not a stretch), /dir needs to have a workable system setup as above in
"2)". I've never tried to install with these options before so can't
really comment. I've seen people complain about dpkg just in general
as well, but I've not used it enough to break something yet I suppose.

4) There are probably other ways to have a certain program installed
twice and also working, such as editing the configuration files before
compiling it, or building the packages yourself, but I know even less
about that.

Well what I intended to be a quick reply got awful long. I do hope you
find some of the above links or explanation useful. I'll be glad if
anyone comes along to expand, clarify, or correct any of what I have
put above.

Best,
~Chris


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