This is the talk I gave at the 2013 CentOS Dojo in Aldershot on spinning custom CentOS live CDs

1. Custom Live Media
Spinning
Jon Cowie, Etsy.com
jcowie@etsy.com
@jonlives
Thursday, 11 July 13

2. Thursday, 11 July 13

3. 1.5 billion page views
$117 million of goods sold
950 thousand users
(in december ‘12)
Thursday, 11 July 13

4. ~800 physical hosts
~300 kvm & lxc VMs
CentOS 5 & 6
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5. Racktables
Cobbler
Chef
Thursday, 11 July 13

6. OldHostBuildProcess
Configure Storage
Configure
Switchports
Configure DNSConfigure Cobbler
Power on HostProfit!
Rack Server Configure ILO
Thursday, 11 July 13

7. NewHostBuildProcess
Configure Storage
Configure
Switchports
Configure DNSConfigure Cobbler
Power on HostProfit!
Rack Server Configure ILO
Gabriel
Thursday, 11 July 13

8. NewHostBuildProcess
Configure Storage
Configure
Switchports
Configure DNSConfigure Cobbler
Power on HostProfit!
Rack Server Configure ILO
Sledgehammer
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9. Sledgehammer
Runs before OS Install
Configures ILO
Configures RAID & GPT
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10. Live CD!
Memory resident
Network bootable*
Easily customisable
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11. Sledgehammer Live CD
Minimal install
Network, disk tools
Ruby & Gems
Sledgehammer “Runner”
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12. Sledgehammer Runner
Mount NFS
Download config
Download payload RPM
Run payload
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13. Sledgehammer Payload
Configure ILO
Set up RAID
Configure GPT
Burn-in tests
Update Racktables
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14. So how does it work?
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15. LiveCD Primer
-isolinux
-initrd0.img
-vmlinuz0
-LiveOS
-squashfs.img
-ext3fs.img
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16. LiveCD Primer
Load kernel and ramdisk
Mount ro / fs
Create rw overlay
Run init
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17. First modification!
Overlay is fixed size.
Copy entire FS to tmpfs
Mount rw / FS
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18. Second modification!
Custom payload
Must run automatically...
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19. /etc/init/start-ttys.conf
...
env
ACTIVE_CONSOLES=/dev/tty[1-­‐6]
...
for
tty
in
$(echo
$ACTIVE_CONSOLES)
;
do
...
initctl
start
tty
TTY=$tty
done
...
Thursday, 11 July 13

20. /etc/init/start-ttys.conf
...
env
ACTIVE_CONSOLES=/dev/tty[1-­‐6]
...
for
tty
in
$(echo
$ACTIVE_CONSOLES)
;
do
...
if
[
"$tty"
==
"/dev/tty1"
]
then
initctl
start
centosdojo
TTY=$tty
else
initctl
start
tty
TTY=$tty
fi
done
...
Thursday, 11 July 13

21. /etc/init/centosdojo.conf
stop
on
runlevel
[012456]
exec
/usr/bin/openvt
-­‐c
1
-­‐w
-­‐f
-­‐-­‐
/opt/centosdojo/runner.rb
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22. So how do I build it?
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23. http://tiny.cc/dojo2013
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