This document describes how to generate a DVD image (.iso) which installs
a minimal CentOS installation where the entirety of the installed system is
build from the provided source.
There are three parts to this document:
How to build binary RPMs from source RPMS
How to build the install disk from the binary RPMS
How to install the minimal system
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How to build the binary RPMs from the source RPMS
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(note - building the binary RPMs is expected to take a long time, ~ 15 hours
on a typical system)
The source RPMs in the "srcs" subdirectory are compiled in an environment
called "mock" which builds each package in a chroot jail to ensure the output
is not influenced by the build system. Mock is controlled by a config file.
The example srcs/build.cfg is provided as a starting point, however it does
to be adjusted for your build environment. In particular, the paths and repo
locations need to be configured for your system. It is highly recommended that
a local mirror of the CentOS repos be used for speed. The example config file
is configured to use an localhost http mirror of the CentOS repos.
To build the binary RPMs from the source RPMs change to the "srcs" subdirectory
and execute the "build.sh" script.
# cd srcs
# ./build.sh
This will use build.cfg and mock to compile every source RPM listed in list.txt.
The output binary RPMs will be in srcs/results. There will also be success.txt
and fail.txt files which list any RPMs that failed to build. Debugging why RPMs
fail to build is beyond the scope of this document, however be aware that RPMs
often fail in the "check" phase of the build (i.e. the package compiled fine
but tests failed). Notably, the python package may fail due to a "test_nis"
failure, and the "attr" and "e2fsprogs" packages may or may not fail depending
on the host file system used for compilation. These failures may or may not be
false positives (for example, the mock environment does not have NIS configured
which is why python's test_nis reports a failure -- the code is actually fine,
we just can't run the test in the mock environment).
To disable the check phase, add the line
config_opts['rpmbuild_opts'] = '--nocheck'
to build.cfg. You can then run build.sh again with list.txt containing
packages which failed:
# cp list.txt list.txt.orig
# cp fail.txt list.txt
# ./build.sh
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How to build the install disk from the binary RPMS
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Once srcs/results is populated with binary RPMs, an installation disk can be
built. Edit the yum.conf file and place an (arbitrary) path for yum log and
cache locations, and make sure that the repository path points to srcs/results.
Run the build_centos.sh script to build the installation DVD:
# ./build_centos.sh
Scroll up the output to the top of the "Spawning worker" messages. You should
observe a line indicating that there are no remaining unresolved dependencies:
...
Installing PKG=dhcp-common PKG_FILE=dhcp-common-4.2.5-42.el7.centos.tis.1.x86_64.rpm PKG_REL_PATH=dhcp-common-4.2.5-42.el7.centos.tis.1.x86_64.rpm PKG_PATH=/localdisk/loadbuild/jmckenna/centos/srcs/results/dhcp-common-4.2.5-42.el7.centos.tis.1.x86_64.rpm from repo local-std
dhcp-common
Debug: Packages still unresolved:
Spawning worker 0 with 4 pkgs
Spawning worker 1 with 4 pkgs
Spawning worker 2 with 4 pkgs
...
This is your confirmation that all required pacakges were found and installed
on the ISO. You should also now see a new file called "centosIso.iso":
# ls -l centosIso.iso
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How to install the minimal system
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The centosIso.iso file can be burned to a DVD or booted in a virtual
environment. It is configured to self-install on boot. After installation,
a user with sudo access must be created manually. The system can then be
booted.
Power the system on with the DVD inserted. A system install will take place
(takes approximately 2 minutes). The system will then report an error and
ask you if you wish to report a bug, debug, or quit. Hit control-alt-F2 to
switch to a terminal window. Enter the following commands to change to the
installed system root, and create a (wrsroot) with sudo access:
cd /mnt/sysimage
chroot .
groupadd -r wrs
groupadd -f -g 345 wrs_protected
useradd -m -g wrs -G root,wrs_protected,wheel -d /home/wrsroot -p cBglipPpsKwBQ -s /bin/sh wrsroot
exit
Change back to the main window with control-alt-F1.
Hit 3 <enter> (the "Quit" option). The system will reboot (make sure you eject
the DVD or use your BIOS to boot from hard disk rather than DVD; the installer
will re-run if the DVD boots again).
You can log into the system as user "wrsroot" with password "wrsroot".
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