Automated FreeBSD Install

For FreeBSD, the ability to PXE boot BIOS and UEFI systems is not new, but documentation frequently assumes an NFS mounted root file system. In my view NFS is unworkable since file access is not logged, and a hung mount is difficult to diagnose.

By using TFTP to pivot to a minroot, then switching to HTTP the entire process can be audited and tailored for individual hosts. This methodology aims to borrow techniques used by an automated install for OpenBSD and Red Hat Linux.

DHCP Services

To PXE-boot FreeBSD there are three components we will need to three components

filename to be loaded by PXE
root-path to be used by the loader
next-server for the custom installation script

# /etc/dhcpd.conf

subnet 192.168.0.0 netmask 255.255.255.0 {
    option routers 192.168.0.7;
    option domain-name-servers 192.168.0.3;
    range 192.168.0.64 192.168.0.254;
    next-server 192.168.2.20;

    host T460S        {
        hardware ethernet c8:5b:76:0d:1c:f3;
        fixed-address 192.168.0.11;
        filename "loader.efi";
        option root-path "tftp://192.168.2.20/freebsd13";
        option host-name "t460s";
    }
}

HTTP Services

The install media can be copied, or mount the ISO as a read-only file system

vnconfig vnd1 /var/www/htdocs/FreeBSD-13.2-RELEASE-amd64-disc1.iso
mount_cd9660 /dev/vnd1c /var/www/htdocs/pub/freebsd13

Distribution files can now be pulled from this http://${next_server}/pub/freebsd13/usr/freebsd-dist/.

Copy loader.efi to /tftpboot/.

Memory File System

Sadly, FreeBSD does not ship a minroot, but we can fetch an image from the mfsBSD project. Mount this ISO in a location where the loader and access boot config and minroot

vnconfig vnd0 /var/www/htdocs/mfsbsd-13.2-STABLE-amd64.iso
mount_cd9660 /dev/vnd0c /tftpboot/freebsd13

This provides everything required to boot

|-- boot
|   |-- defaults
|   |   `-- loader.conf
|   |-- device.hints
|   |-- kernel
|   |   |-- acpi_*.ko
|   |   |-- ahci.ko
|   |   |-- kernel.gz
|   |   `-- linker.hints
|   |-- loader
|   |-- loader.conf
|   `-- lua
|       |-- cli.lua
|       |-- color.lua
|       |-- config.lua
|       |-- core.lua
|       |-- drawer.lua
|       |-- gfx-*.lua
|       |-- hook.lua
|       |-- loader.lua
|       |-- menu.lua
|       |-- password.lua
|       `-- screen.lua
|-- boot.config
`-- mfsroot.gz

boot/loader.conf provides the configuration for switching to a memory file system

mfs_load="YES"
mfs_type="mfs_root"
mfs_name="/mfsroot"
ahci_load="YES"
vfs.root.mountfrom="ufs:/dev/md0"

For a standard build mfsroot.gz is about 70MB.

Building a Custom Miniroot

The mfsBSD root image can be modifed to kick off a custom install script. In the mfsbsd root, modify conf/rc.local.sample. The steps are:

Find http server and host name from dhclient leases
Fetch sources
Fetch install configuration by hostname
Launch bsdinstall in a tmux session

export PATH=/usr/local/bin:$PATH

for op in `awk '/^(  |  option )(next-server|host-name|domain-name) / { gsub("-", "_", $(NF-1)); print $(NF-1)"="$NF }' /var/db/dhclient.leases.*`
do
    eval "$op"
done

mkdir /usr/freebsd-dist
cd /usr/freebsd-dist
for dist in MANIFEST kernel.txz base.txz; do
    fetch http://${next_server}/pub/freebsd13/usr/freebsd-dist/${dist}
done
cd -

fetch http://${next_server}/bsdinstall/${host_name}.cfg
echo "Starting autoinstall"
tmux new-session -s autoinstall -d
tmux send-keys -t autoinstall:0 "bsdinstall script ${host_name}.cfg" C-m

To build:

cd mfbsd-master
make clean-all BASE=/home/eradman/13.2-RELEASE/usr/freebsd-dist
make BASE=/home/eradman/13.2-RELEASE/usr/freebsd-dist
make iso BASE=/home/eradman/13.2-RELEASE/usr/freebsd-dist

Host Configuration

The installation bootstrap is based into the custom miniroot, but the host configuration is fetched from the installer set by the DHCP option