Centos Image Builder
This repo allows one to create custom CentOS images for use with Triton.
Configuration files and scripts that are common to many images should be maintained in sdc-vmtools.
Requirements
In order to use this repo, you need to have a SmartOS "joyent" brand zone that is capable of running qemu. In order to run qemu the instance needs customization beyond what can be done with Triton APIs. That is, an operator needs to customize the instance. This is typically accomplished by running the following commands on the apprporiate compute node:
uuid=XXX # Change this to the instance uuid
topds=zones/$uuid/data
zfs create -o zoned=on -o mountpoint=/data $topds
zonecfg -z $uuid <<EOF
add dataset
set name=$topds
end
add fs
set dir=/smartdc
set special=/smartdc
set type=lofs
set options=ro
end
add device
set match=kvm
end
EOF
Setup
This relies on the sdc-vmtools repo as a submodule. You can get the right version of that with:
git submodules update --init
If you forget to do that, create-image will do it before it tries to use
anything from that submodule.
Using
To generate a CentOS <version> image run:
# ./create-image -r <version>
While the primary focus of create-image is CentOS, it should be
straight-forward to generate RHEL and Fedora images with this repo. Once
support is added, other distributions may be specified with the -d option.
Other repositories provide equivalent
functionality for other distribution types.
$ ./create-image -h
Usage:
./create-image [options] [command ...]
option:
-h This message
-d Distro name. One of centos, redhat, fedora
-r Distro release
Commands:
fetch Fetch the installation ISO
ks_iso Create a kickstart ISO
image Generate the image
fetch
Download the distribution's NetInstall media (.iso) and verify its integrity. If the required ISO already exists, its integrity is verified. If it is found to be corrupt it is fetched again.
This image will be automaticlaly mounted at /run/install/repo during
installation.
ks_iso
Generate a kickstart ISO image. This will contain the following:
ks.cfg- From<distro>-<release>/ks.cfg.sdc-vmtools- The current content of the sdc-vmtools repo.
This image is not automatically mounted, but may be mounted via %pre or
%post blocks within ks.cfg. It has kickstart as its volume name, making
it easy to find under /dev/disk/by-name. For example:
%pre
#! /bin/bash
set -ex
mkdir /run/install/joyks
mount /dev/disk/by-name/kickstart /run/install/joyks
%end
image
This runs qemu in a way that allows unattended installation using the media and
kickstart ISO images described above. Once qemu exits, a Triton-compatible
image is generated and stored in the current directory as
<distro>-<release>-<timestamp>.{json,tar.gz}.
The actual image creation is handled by sdc-vmutils/bin/create-hybrid-iamge.
Default Settings For Images
Each image has the following characteristics. See
<distro>-<release>/ks.cfg for details on which packages are included.
- Disk is 10GB in size (8GB for / and the rest for swap)
- Stock Kernel
- US Keyboard and Language
- Firewall enabled with SSH allowed
- Passwords are using SHA512
- Firstboot disabled
- SELinux is set to permissive
- Timezone is set to UTC
- Console is on ttyS0
- Root password is blank: console login is allowed without a password
- Configuration from the SmartOS metadata service is performed using cloud-init.
Development
The following serves as a guide for adding support for new RHEL-like distributions and versions of existing distributions.
Distribution-specific content is found in a per-distro subdirectory. For
example, CentOS 7 bits are in the centos-7 directory. Directory names are
always lower-case.
The following subsections describe the content that may be in a per-distro directory.
ks.cfg file
The kickstart configuration file. Notable parts of this include:
cloud-initis installed, as it is responsible for interacting with the host's metadata service to configure networking, run user scripts, etc. It requirespyserial, but for "reasons" the cloud-init developers have avoided adding pyserial as a dependency.cloud-initrequires configuration in/etc/cloud/cloud.cfg.d/90\_smartos.cfgto only enable the SmartOS datasource, among other things.- A
%preblock is used to tail the most useful installation logs and write them to/dev/ttyS0.qemuruns in such a way that the guest'sttyS0appears onqemu'sstdout, thus allowing the installation log to be captured by Jenkins or similar automation that may be creating an image. - Before trying to copy anything from the
sdc-vmtoolssubdirectory of the kickstart ISO, the ISO must be mounted as described above.
Each %pre and %post section should begin with the following, with a unique
JOYENT_STATUS_<foo> tag for each. If the set of tags used does not exactly
match JOYENT_STATUS_PRE JOYENT_STATUS_POST,
<distro>-<release>/create-image-overrides.sh must declare JOYENT_STATUS_VARS
as an array of the expected tags.
#! /bin/bash
joyent_status=fail
trap 'echo JOYENT_STATUS_PRE=$joyent_status' EXIT
set -ex
and end with:
set +x
joyent_status=ok
create-image will verify that all JOYENT_STATUS_<foo> tags are set to ok,
which only happens if the script in that section runs to completion.
RPMS directory
Any \*.rpm file in this directory will be copied to the Packages subdirectory
of the kickstart ISO.
This directory does not exist if not needed.
RPMS.remote file
A list of RPM files that will be downloaded and stored in the Packages
subdirectory of the kickstart ISO. See RPMS directory above.
This file does not exist if not needed.
keys directory
Each GPG key found in the keys directory will be imported into the keyring of
the user running this command. These keys are used for authenticating the media
that is downloaded by the fetch command.
create-image-overrides.sh
If the distribution requires overrides of any functionality, it should be added
here. This file is sourced by create-image just before processing commands.
In general, the global variables that are all-uppercase are good candidates for
being overridden.
This file does not exist if not needed.
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