Re: experimenting with dpkg: installing on a different system
On Fri, Jun 20, 2014 at 11:42 AM, <berenger.morel@neutralite.org> wrote:
>
> First, a warning: I am basically trying to reinvent a wheel, only for my
> pleasure and knowledge. So, yes, there are easier ways to do the things.
>
> Yesterday, I was experimenting with dpkg ( for my own fun, and to learn
> things ), especially with the parameter "--root" which change the targeted
> system. Or, to be more exact, to change the directories where it tries to
> retrieve it's own informations ( /var/lib/dpkg ) and where it tries to
> deploy stuff ( / ).
>
> Note that I did not tried debootstrap(*).
>
> What I tried to do was basically to "replace" the debian installer:
>
> On an external hard disk:
>
> Basic setup:
> * using gparted to partition and format according to my wishes ( a portable
> system able to boot from kali live-cd, tail live-cd, an installed Debian
> testing, a partition dedicated to experimenting another linux-based distro,
> and a partition to boot a BSD kernel based system. Yes, probably
> Debian/kFreeBSD in a first time, since I have some knowledge about how
> Debian works, so that I would not start from void. Of course, other utility
> partition for /home, /tmp and /share for windows interaction, can be useful.
> Something odd and stupid enough to allow me to lose a lot of time in
> tinkering :p )
> * mounted the future "/" partition on "/mnt"
> * created the basic filesystem, mirroring what I have on my working system (
> /root, /mnt, /boot, /var, /etc, et cetera )
> * mounted partitions on their mount points
>
> Some tinkering:
> * created the dpkg's var tree: "cd /mnt; mkdir -p /var/lib/dpkg; touch
> /var/lib/dpkg/available; /var/lib/dpkg/status"
> * made an alias for dpkg so that I would not do an error: "alias dpkg=dpkg
> --root=/mnt"
>
> Identifying the first set of packages to install so that things would be
> configured by standard dpkg's methodology:
> * I want dpkg to be correctly configured, not only a hand-made tree, so it
> is my first target.
> * dpkg depends on various packages ( on my testing current system ), namely:
> libc6, tar, libselinux1, liblzma5, libbz2-1.0, zlib1g. From those ones, I
> know that the one which will be need by almost all packages is libc6, so
> let's identify which packages it needs.
> * libc6's dependencies: libgcc1, which depends on libc6, gcc-4.9-base (
> which depends on nothing, nice! ) but most importantly, pre-depends on
> multiarch-support ( which depends itself on libc6 ).
>
> Trying to install the first set of ( 4 ) packages through dpkg:
> * dpkg --root /mnt -i /var/cache/apt/archives/libc6_*.deb
> /var/cache/apt/archives/gcc-4.9-base_*.deb
> /var/cache/apt/archives/libgcc1_*.deb
> /var/cache/apt/archives/multiarch-support_*.deb
>
> When it comes to libc6, dpkg report an error of being unable to find various
> scripts, like IIRC "/var/lib/dpkg/tmp.ci/preinst" ( in the chrooted
> environment, so /mnt/var/lib/dpkg/tmp.ci/preinst ).
> I have tried to fool dpkg by creating those files, making them empty and
> executable, the error is the same, so my guess is that dpkg really can find
> them ( since it can delete them ). Maybe a right problem? I did not at the
> moment tried to set the rights to 777 on /var/lib/dpkg.
> Setting to maximum the debugging options of dpkg did not helped at all, too
> ( almost no informations ) and same when I tried the --force-all option. I
> still did not tried to just copy stuff, which could work since I believe
> that it's what debootstrap does (not checked in source code, programming in
> bash is still very obscure for me. I might try to take a look at
> cdebootstrap thought, since it is written in C which is far more readable
> for me).
>
> Any idea of tricks I might try or stuff I might read? In dpkg's man, it is
> said that package's managers which want to understand how dpkg install their
> packages should not refer to this man, so I guess it would be a good start
> to know where is stored the recommended doc for them. I'm not a package
> maintainer, but it sounds obvious that for this small game of mine, I need a
> real knowledge of dpkg.
>
> *: I do not use debootstrap, but I perfectly know that it is made to install
> from a running GNU/Linux distro.
> I "just" want to experiment, after all, for learning. And I think that it
> might have some issues with my intent:
> * should I use debootstrap or cdebootstrap?
> * It seems it is possible to specify various list of packages to installs,
> but can I tweak them? Each time I install from a strictly minimal scratch, I
> spend some times to remove packages that I know I will not need, and to set
> many, many other as automatically installed. ( and only after that, I am
> adding packages which are really useful to me, so that I can have "really"
> minimal systems )
> * it seems it needs the user to chroot after the bootstrap, which means the
> user have to be root. I do not see why it should be mandatory to be root (
> with all problems it might cause ) to install a distro on an external drive.
>
> How to specify which packages to install -- since I always remove a lot of
> packages after a strictly minimal Debian installation... which is made from
> debootstrap if I have understood correctly the few source lines of this
> script I have read -- ? And how could it be possible to do a remote install?
> How can it be used without being root? And I think those things might be
> avoided with dpkg. Except that... I had some issues I did not understood, of
> course.
It's too bad that apt-get doesn't have the equivalent of yum's
"--installroot" because you wouldn't have to download and feed dpkg
debs and their dependencies. Since Debian has debootstrap, an apt
"--installroot" option isn't really necessary.
The debootstrap "--variant=minbase" option installs the following:
# debootstrap --arch=amd64 --print-debs --variant=minbase sid
/home/minbase http://ftp.uk.debian.org/debian/
W: Cannot check Release signature; keyring file not available
/usr/share/keyrings/debian-archive-keyring.gpg
I: Retrieving Release
I: Retrieving Packages
I: Validating Packages
I: Resolving dependencies of required packages...
I: Resolving dependencies of base packages...
I: Found additional required dependencies: insserv libaudit-common
libaudit1 libbz2-1.0 libcap2 libdb5.3 libdebconfclient0
libsemanage-common libsemanage1 libslang2 libustr-1.0-1
I: Found additional base dependencies: debian-archive-keyring gnupg
gpgv libapt-pkg4.12 libreadline6 libstdc++6 libusb-0.1-4
readline-common
base-files base-passwd bash bsdutils coreutils dash debconf
debconf-i18n debianutils diffutils dpkg e2fslibs e2fsprogs findutils
gcc-4.7-base gcc-4.8-base gcc-4.9-base grep gzip hostname initscripts
insserv libacl1 libattr1 libaudit-common libaudit1 libblkid1
libbz2-1.0 libc-bin libc6 libcap2 libcomerr2 libdb5.3
libdebconfclient0 libgcc1 liblocale-gettext-perl liblzma5 libmount1
libncurses5 libpam-modules libpam-modules-bin libpam-runtime libpam0g
libpcre3 libselinux1 libsemanage-common libsemanage1 libsepol1
libslang2 libss2 libtext-charwidth-perl libtext-iconv-perl
libtext-wrapi18n-perl libtinfo5 libustr-1.0-1 libuuid1 login lsb-base
mawk mount multiarch-support ncurses-base ncurses-bin passwd perl-base
sed sensible-utils startpar sysv-rc sysvinit sysvinit-core
sysvinit-utils tar tzdata util-linux zlib1g apt debian-archive-keyring
gnupg gpgv libapt-pkg4.12 libreadline6 libstdc++6 libusb-0.1-4
readline-common
I: Deleting target directory
Two guesses:
If there's a package in the above list that you don't want to install,
you can use "--exclude=" but since they look like their priorities are
"essential" and "required", I'd be surprised if they could be
excluded.
However if you want to exclude "net-tools", for example, from a
debootstrap run without "--variant=minbase", you should be able to do
so because its priority is "important".
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