From 8f78d7ac1e4e187fcfe973d1e84308cf870ba9a2 Mon Sep 17 00:00:00 2001 From: Stefan Kreutz Date: Sat, 24 Jul 2021 20:12:02 +0200 Subject: Release installiso 0.1.0 --- posts/first-release-of-installiso.md | 183 +++++++++++++++++++++++++++++++++++ 1 file changed, 183 insertions(+) create mode 100644 posts/first-release-of-installiso.md (limited to 'posts/first-release-of-installiso.md') diff --git a/posts/first-release-of-installiso.md b/posts/first-release-of-installiso.md new file mode 100644 index 0000000..c0d5502 --- /dev/null +++ b/posts/first-release-of-installiso.md @@ -0,0 +1,183 @@ +--- +title: "First release of installiso" +description: "A utility to customize OpenBSD installation images for unattended installation." +published: 2021-07-24 +--- + +One year ago I [posted](/posts/autoinstall-openbsd-on-qemu/) how to script an unattended installation of OpenBSD on the QEMU virtual machine monitor on Linux. +The script involved setting up a complicated network boot environment because I treated the installation image as a black box. +Of course, I could have mounted the ISO 9660 image and created a modified image using [`mkisofs(8)`](http://cdrtools.sourceforge.net/private/man/cdrecord/mkisofs.8.html). +But I didn't know how to insert the [`autoinstall(8)`](https://man.openbsd.org/OpenBSD-6.9/autoinstall) response file into the RAMDISK kernel in the ISO 9660 image. +That was no surprise -- why would anyone need to change an OpenBSD kernel on Linux. + +OpenBSD, on the other hand, includes adequate utilities. +Thanks to [`vmctl(8)`](https://man.openbsd.org/OpenBSD-6.9/vmctl), [`rdsetroot(8)`](https://man.openbsd.org/OpenBSD-6.9/rdsetroot), and [`mkhybrid(8)`](https://man.openbsd.org/OpenBSD-6.9/mkhybrid), we can modify the ISO 9660 image _and_ the contained RAMDISK kernel. +The exact process is a bit tedious so I decided to automate it. +The resulting script is more hacky than pretty but it gets the job done and I found it useful enough to give it a name, `installiso`, and release it today. +Currently, it's limited to the _amd64_ architecture, though it should work on other architectures alike. +You can download the very first release [here](/files/installiso-0.1.0.tar.gz). +The man page is also viewable [here](/files/installiso.8-0.1.0.html). +Feedback appreciated! + +In the remainder of this post I'll show how to use `installiso` to create custom OpenBSD installation images for unattended -- and possibly offline -- installation. +As an example, I'll show how to create virtual machines on OpenBSD's own virtual machine monitor, [`vmm(4)`](https://man.openbsd.org/OpenBSD-6.9/vmm). +Finally, I'll list the concrete commands necessary to patch an installation image without `installiso` because I would want to know how it works. + +## Installation + +You can install the `installiso` utility as follows. + + $ ftp https://www.skreutz.com/files/installiso-0.1.0.tar.gz + $ tar -xzf installiso-0.1.0.tar.gz + $ cd installiso-0.1.0/ + $ doas make install + $ man 8 installiso + +Alternatively, you can run `./installiso.ksh` without installation. + +## Usage + +Given a response file `install.conf`, and a file-specific file set `site/`, you can download, verify, and customize an official installation image as follows. + + $ installiso -v fetch -r 6.9 + $ doas installiso -v \ + patch -i install.conf -s site/ install69.iso custom.iso + +You can also specify a mirror, another release or the latest development snapshot, and a [`signify(1)`](https://man.openbsd.org/OpenBSD-6.9/signify) public key if you like. +See the [man page](/files/installiso.8-0.1.0.html). + +## Example + +You can create a virtual machine on OpenBSD's own virtual machine monitor, [`vmm(4)`](https://man.openbsd.org/OpenBSD-6.9/vmm), as follows. + +First, we create an [`autoinstall(8)`](https://man.openbsd.org/OpenBSD-6.9/autoinstall) response file. +Here, we'll setup a regular user and authorize an [`ssh(1)`](https://man.openbsd.org/OpenBSD-6.9/ssh) public key. +Of course, you can skip this step and have the installer mail you the responses recorded during an interactive installation instead. + + $ cat >install.conf <site/install.site < /etc/installurl + + # Permit user group wheel to run any command as root + # without entering their password using doas(1). + echo "permit nopass keepenv :wheel" > /etc/doas.conf + + # Install packages on the first boot. + echo "pkg_add sqlite3" >> /etc/rc.firsttime + EOF + $ chmod +x site/install.site + +Third, fetch and patch an installation image as above. + + $ installiso -v fetch -r 6.9 + $ doas installiso -v \ + patch -i install.conf -s site/ install69.iso custom.iso + +Forth, we start a virtual machine off a new disk image and the custom installation image. +The OpenBSD FAQ contains a good [introduction](https://www.openbsd.org/faq/faq16.html) to [`vmm(4)`](https://man.openbsd.org/OpenBSD-6.9/vmm). +I assume you've setup the network option 2. + + $ vmctl create -s 10G disk.qcow2 + $ doas vmctl start -c -i 1 -L -m 512M -d disk.qcow2 \ + -r custom.iso tmp + +Finally, we can log into the new virtual machine once the unattended installation has completed. + + $ ssh \ + -o "StrictHostKeyChecking no" \ + -o "UserKnownHostsFile /dev/null" \ + 100.64.1.3 + +## Disklabel template + +In the above example, the OpenBSD installer allocates all disk space automatically, see [`disklabel(8)`](https://man.openbsd.org/OpenBSD-6.9/disklabel). +You can supply a custom disklabel template instead if you need more control. + +First, create a disklabel template. + + $ cat >disklabel_template <> install.conf + +Finally, serve the file during the unattended installation. + + $ printf 'HTTP/1.0 200 OK\n\n' | + cat - disklabel_template | + nc -lN 8080 + +## Inner workings + +The `installiso patch` command used above + + $ doas installiso -v \ + patch -i install.conf -s site/ install69.iso custom.iso + +boils down to the following commands -- excluding error handling, temporary files, command-line options, etc. + +First, we extract the ISO 9660 image. + + # vnconfig vnd0 install69.iso + # mount -t cd9660 /dev/vnd0c /mnt + # mkdir cd + # tar -C /mnt -c -f - . | tar -C cd -x -p -f - + # umount /mnt + # vnconfig -u vnd0 + +Second, we patch the RAMDISK kernel. + + # gzip -d -o bsd.rd cd/6.9/amd64/bsd.rd + # rdsetroot -x bsd.rd disk.fs + # vnconfig vnd0 disk.fs + # mount /dev/vnd0a /mnt + # install -o root -g wheel -m 0644 -C \ + install.conf /mnt/auto_install.conf + # umount /mnt + # vnconfig -u vnd0 + # rdsetroot bsd.rd disk.fs + # gzip -9fnq bsd.rd + +Third, we insert the patched kernel and the site-specific file set into the extracted ISO 9660 image. + + # install -o root -g 2000 -m 0755 -C \ + bsd.rd.gz cd/6.9/amd64/bsd.rd + # ( cd site/ && tar -c -z -f ../cd/6.9/amd64/site69.tgz . ) + # ( cd cd/6.9/amd64/ && ls -l > index.txt ) + +Finally, we create the bootable ISO 9660 image. + + # mkhybrid -a -R -T -L -l -d -D -N -o custom.iso \ + -A "Custom OpenBSD 6.9 amd64 Install CD" \ + -b 6.9/amd64/cdbr -c 6.9/amd64/boot.catalog \ + cd + -- cgit v1.2.3