linux · tech · tips

Barebone Kickstart setup for CentOS 7

Since I had to install a bunch of baremetal servers and I haven’t had the time to checkout Foreman yet, I created a minimal setup to be able to use a Kickstart file.

My early iterations were done in Packer, then I switched to the baremetal servers to work out the details.

Please note: this is an automated install that WILL DELETE EVERYTHING on /dev/sda !!!

The kickstart file

This kickstart file has been made iterating over CentOS 6 and CentOS 7 default install kickstart files (those generated by the installer), with a couple of changes based on the documentation and similar examples (many thanks to Jeff Geerling !).

Please note: this is an automated install that WILL DELETE EVERYTHING on /dev/sda !!! – Do not run it on the wrong system!

Also, this is just a “template”, make sure to change it where it makes sense, for example the partitioning scheme and the root password. For the network settings, see below the script to customize and serve the kickstart file over http.

template.cfg

# Run the installer
install

# Use CDROM installation media
cdrom

# System language
lang en_US.UTF-8

# Keyboard layouts - Change this!
keyboard --vckeymap=it --xlayouts='it','us' --switch='grp:alt_shift_toggle'

# Enable more hardware support
unsupported_hardware

# Network information - the --device=link option activates the specific IP address on the first interface with a link up
# the ZZNAMEZZ labels will be changed later with sed, to customize the installation
network  --bootproto=static --device=link --gateway=ZZGATEWAYZZ --ip=ZZIPADDRZZ --nameserver=ZZDNSZZ --netmask=ZZNETMASKZZ --noipv6 --activate
network  --hostname=ZZHOSTNAMEZZ

# System authorization information
auth --enableshadow --passalgo=sha512

# Root password - Change this!
rootpw YOUR_SECURE_PASSWORD

# System timezone - Change this!
timezone Europe/Rome --isUtc --nontp

# Run the text install
text

# Skip X config
skipx

# Only use a specific disk, Change the drive here!
ignoredisk --only-use=sda

# Overwrite the MBR
zerombr

# Partition clearing information
clearpart --all --initlabel --drives=sda

# System bootloader configuration - Change the drive here
bootloader --location=mbr --boot-drive=sda


# PARTITIONING
# This is our partitioning scheme, change it where required

# this might not be required
part biosboot --fstype="biosboot" --ondisk=sda --size=1

# this is required
part /boot --fstype="xfs" --ondisk=sda --size=1024

# this will create a Volume Group "VGsystem" spanning the whole disk (except for the /boot partition)
part pv.229 --fstype="lvmpv" --ondisk=sda --size=200000 --grow
volgroup VGsystem --pesize=4096 pv.229

#
logvol /         --fstype="xfs"   --size=10240  --label="ROOT"  --name=LVroot  --vgname=VGsystem
logvol /usr      --fstype="xfs"   --size=20480  --name=LVusr    --vgname=VGsystem
logvol /var      --fstype="xfs"   --size=20480  --name=LVvar    --vgname=VGsystem
logvol /var/log  --fstype="xfs"   --size=20480  --name=LVvarlog --vgname=VGsystem

logvol swap      --fstype="swap"  --size=16384  --name=LVswap   --vgname=VGsystem

logvol /tmp      --fstype="xfs"   --size=10240  --name=LVtmp    --vgname=VGsystem
logvol /home     --fstype="xfs"   --size=51200  --name=LVhome   --vgname=VGsystem
logvol /opt      --fstype="xfs"   --size=20480  --name=LVopt    --vgname=VGsystem


# Do not run the Setup Agent on first boot
firstboot --disabled

# Accept the EULA
eula --agreed

# System services - we disable chronyd because we use NTP
services --disabled="chronyd" --enabled="sshd"


# Reboot the system when the install is complete
reboot


# Packages

%packages --ignoremissing --excludedocs
@^minimal
@core
kexec-tools
%end

%addon com_redhat_kdump --disable

%end

# upgrade the system before rebooting

%post
yum -y upgrade
yum clean all
%end

Customizing and serving the kickstart file

As we mentioned earlier, I made a pretty simple script to customize the kickstart template and serve it over http.

Please note: this is an automated install that WILL DELETE EVERYTHING on /dev/sda !!!

serve_kickstart.sh

#!/bin/bash

gateway="192.168.0.1"
netmask="255.255.255.0"
dns="192.168.0.11,192.168.0.12"

# this is pretty hacky, sorry
local_ipaddr=$(ip -4 -o addr show dev eth0 | awk {'print $4'} | cut -d/ -f1)

# accepts hostname and ip address on the command line
server_hostname="$1"
server_ipaddr="$2"

if [ -z "$server_hostname" ]; then
    server_hostname="freshinstall.stardata.lan"
    echo "Using '$server_hostname' as default."
fi

if [ -z "$server_ipaddr" ]; then
    server_ipaddr="192.168.0.99"
    echo "Using '$server_ipaddr' as default IP address."
fi


# create the file to customize
/bin/cp -f template.cfg custom.cfg

# customize the kickstart file
sed -i "s/ZZGATEWAYZZ/$gateway/g" custom.cfg
sed -i "s/ZZIPADDRZZ/$server_ipaddr/g" custom.cfg
sed -i "s/ZZDNSZZ/$dns/g" custom.cfg
sed -i "s/ZZNETMASKZZ/$netmask/g" custom.cfg
sed -i "s/ZZHOSTNAMEZZ/$server_hostname/g" custom.cfg

# create the file to serve
/bin/mv -f custom.cfg c7.cfg

# write the instructions to add to the boot on screen
echo "To use this kickstart, add to the boot command line: "

echo -e "\nip=${server_ipaddr} netmask=${netmask} gateway=${gateway} dns=${dns} text ks=http://${local_ipaddr}:8000/c7.cfg\n\n"

sleep 3

python -m SimpleHTTPServer

This is what an example run looks like:

$ ./serve_kickstart.sh test01.stardata.lan 192.168.0.100
To use this kickstart, add to the boot command line:

ip=192.168.0.100 netmask=255.255.255.0 gateway=192.168.0.1 dns=192.168.0.11,192.168.0.12 text ks=http://192.168.0.200:8000/c7.cfg

Serving HTTP on 0.0.0.0 port 8000 ...

192.168.0.100 - - [20/Apr/2018 16:03:43] "GET /c7.cfg HTTP/1.1" 200 -

If you take a look at the c7.cfg that is served via http on port 8000, you’ll see that the relevant network placeholders have been swapped with the custom values from the script:

$ grep ^network c7.cfg
network  --bootproto=static --device=link --gateway=192.168.0.1 --ip=192.168.0.100 --nameserver=192.168.0.11,192.168.0.12 --netmask=255.255.255.0 --noipv6 --activate
network  --hostname=test01.stardata.lan

As usual, I hope this helps some fellow admin out there.

References

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