[CentOS] Installing on partitionable RAID arrays

RedShift redshift at pandora.be
Thu Mar 26 13:31:30 UTC 2009


RedShift wrote:
> Hello
> 
> 
> Since linux 2.6, the md layer has a feature called partitionable arrays. So instead of having two disks, creating an identical partition table on both and then putting those partitions in RAID 1, you take those two disks and put them in one partitionable RAID 1 array (in mdadm terms, "mdp") and create a partition table on the new RAID device. The advantages are quite clear compared to the old non-partitionable arrays.
> 
> My question is, is this supported by CentOS? The GTK installer doesn't provide a way to create such an mdp device and the integrated partitioning tool does not see for example md_d0 when I create it manually from the console.
> 
> Another way to get CentOS on such a configuration would be to do everything manually, thus installing the base system by creating the necessary disk allocations and then rpm -i all the required packages to get it to boot. (I've done this before, it's not a big deal, you just need to follow a certain order - I remember documenting it somewhere but forgot). But since this method is probably not officially documented anywhere or even supported I'll most likely won't get any support if this setup were to fail somehow (like when upgrading between minor versions).
> 
> I've tried STFW'ing, but searching for centos and partitionable arrays is too ambiguous.
> 
> 
> Thanks,
> 
> 
> Best regards,
> 
> 
> Glenn Matthys 


As a follow-up, I found the documentation I wrote how to install CentOS without any installer:


# First, setup your disks to your liking. You can use whatever you want here,
# RAID, LVM, etc... Remember your disk configuration because you'll need it
# to configure grub, menu.lst and fstab. Using RAID, LVM, or others will require
# more configuration than this guide covers. To keep it simple I'm using a
# single disk. An example:

$ fdisk /dev/sda
$ mount /dev/sda3 /target
$ mkdir /target/boot
$ mount /dev/sda1 /target/boot

# Depending on the host OS you're using, you may need to initialize the rpm db
# on the host OS
$ rpm --initdb

# Use the following command to install the packages. I'll be addressing this
# command as $rpm.

$ rpm --root /target -i 

# Use your shell's tab completion to complete the package filenames. I
# deliberatly left out the versions so these instructions apply to a wide range
# of versions

# Let's install some basics
$rpm setup basesystem filesystem

# Install bash first, this is needed for post-install scripts
$rpm bash glibc glibc-common termcap libgcc tzdata mktemp libtermcap

# Install some dependencies (this is mainly to keep the next command smaller)
$rpm grep pcre libstdc++ info ncurses zlib gawk sed ethtool

# Install the bulk of the system
$rpm coreutils libselinux libacl libattr pam audit-libs cracklib-dicts \
cracklib libsepol mcstrans libcap chkconfig python db4 openssl readline \
bzip2-libs gdbm findutils krb5-libs initscripts util-linux popt udev MAKEDEV \
centos-release shadow-utils keyutils-libs iproute sysfsutils SysVinit \
net-tools module-init-tools e2fsprogs e2fsprogs-libs glib2 mingetty \
device-mapper sysklogd psmisc centos-release-notes procps libsysfs iputils 

# Install package manager
$rpm rpm beecrypt elfutils-libelf rpm-libs sqlite

# Install YUM
$rpm yum python-elementtree rpm-python yum-metadata-parser python-sqlite \
expat libxml2 python-urlgrabber m2crypto python-iniparse


# You may also want to install your favorite editor
$rpm nano

# This provides /root with some defaults, like color highlighting on `ls`
$rpm rootfiles

# Right now you have system which you can chroot to, so we can start setting up
# the basics

# Mount directories for chroot operation
$ mount --bind /dev /target/dev
$ mount -t proc none /target/proc
$ mount -t sysfs none /target/sysfs
$ chroot /target

# This constructs /etc/shadow
$ pwconv

# Configure fstab
$ nano -w /etc/fstab

# Installing the kernel. Do this back outside the chroot in the host OS system
$ exit
$rpm kernel mkinitrd cpio device-mapper-multipath dmraid gzip kpartx lvm2 nash \
tar less device-mapper-event

# Install the bootloader, grub.
$rpm grub diffutils redhat-logos

# Let's chroot again to configure our bootloader
$ chroot /target

# We start by configuring the bootloader. Open /boot/grub/menu.lst, and put the
# following there

<<<MENU.LST
timeout 5
default 0

# (0) CentOS
title CentOS
root (hd0,0)
kernel /vmlinuz-2.6.18-92.el5 root=/dev/sda3 ro
initrd /initrd-2.6.18-92.el5.img
>>>

# If this command gives an error, you can safely ignore this because it's not
# of importance. What is important is that grub-install copied the right files
# to /boot/grub that we need for booting.
$ /sbin/grub-install /dev/sda

# Manually install grub if the previous step failed. - means type it in the grub
# shell
$ grub
$- root (hd0,0)
$- setup (hd0)

# Optional packages
# You may want to install passwd so you can set passwords ;-)
$rpm passwd libuser openldap cyrus-sasl-lib

# These are used to set the keyboard language (loadkeys)
$rpm kbd usermode


# ** Right now you should have a bootable system! Here are some tips to help you
# through your 1st boot ***

# Most of the system configuration happens in /etc/sysconfig. See

/usr/share/doc/initscripts

for full documentation.

Some quick post-install tips:
* Configure your keyboard in 
/etc/sysconfig/keyboard
using the KEYTABLE variable

* Configure networking
Take a look at /etc/sysconfig/network-scripts. See ifcfg-lo for an example.

# This recreates the RPM database. If the host OS you used has a different
# version of db, rpm will complain with
# rpmdb: unable to lock mutex: Invalid argument
$ rpmdb --rebuilddb


Best regards,


Glenn Matthys

(PS: I've also attached the documentation as install_centos.txt, but mailman will probably strip it)
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