OpenBSD 6.2 on BeagleBone Black
-------------------------------
Last edited: $Date: 2018/01/04 14:01:03 $
## BeagleBone Black
The BeagleBone Black (http://beagleboard.org/BLACK) is an Arm-7
development board with a AM335x 1GHz ARM Cortex-A8processor, 512 Mb
DDR3 RAM, ethernet, microD slot, 4GB 8-bit eMMC on-board flash
storage and a lof other nice goodies. This board is capable of
running OpenBSD :)
In order to install OpenBSD on this board, you will need to access
the serial console. This is a 3.3 Volt RS232 serial console, and
connecting this with a 12 or even 5 Volt serial port will be fatal
for the board. You need an USB F-cable to connect the BeagleBone
Black serial port to your laptop or computer.
## Connecting the Serial Port
Locate the pins of the serial board on the BeagleBone Black. The
white dot is next to pin 1.
Use the following pins:
* pin 1: Ground
* pin 4: Receive
* pin 5: Transmit
I have made a photo where you can see the USB F-cable connected to
the serial console, you can find it here:
gopher://box.matto.nl/I/images/bbb-serial.jpg
I connected the other end (with the USB-connector) with a Debian
Linux laptop and started minicom. In minicom, choose for
* Baud 115,200
* Bits 8
* Parity N
* Stop Bits 1
* Handshake None
Boot the board and check that you see the startup-messages.
Bring the board down.
## OpenBSD Installation image
For the BeagleBone Black you need the miniroot-am335x-62.fs
installfile from one of the OpenBSD ftp-mirrors.
You can copy this file with dd to a micro SD-card. I did this on a
Debian Linux laptop with:
dd if=miniroot-am335x-62.fs of=/dev/mmcblk0 bs=16k
Funny thing is that you can use the same micro SD-card to install
OpenBSD on :)
So you dd the install image to a micro SD-card, start the installer
from there and install OpenBSD on the same card...
## Get the sets
This step is optional, just to make things easier.
I downloaded the setfiles from one of the OpenBSD ftp-mirrors:
- base62.tgz
- BOOTARM.EFI
- bsd
- bsd.rd
- BUILDINFO
- comp62.tgz
- index.txt
- man62.tgz
- SHA256
- SHA256.sig
I put these files on a local webserver, so during the install the
installation program can fetch these files from the local network.
I didn't bother to download any x-sets, this board will be running
headless.
## Start the installer
Now the hard work is done. Put the micro SD-card in the slot on the
board. Locate the small switch on to top-side of the board, close to
the micro SD-card slot (on the bottom-side). Keep this switch
pressed while putting power on the board. The board will now attempt
to install from the external micro SD-card and not from the internal
eMMC-flash storage.
The OpenBSD installer will start. Just follow the installation
procedure, At the choice which hard disk to partition, choose sd0.
Because this BeagleBone will mount its /home as memory file system
I choose for edit the partition table, removed the home partition
and changed the size of the /usr partition.
After the installation is done reboot.
## Reboot into the installed system
After the reboot, login again via the serial cable and have a look
around your fresh OpenBSD system.
## Protect the micro SD card by mounting it readonly
To protect the life of the SD-card, we are going to make it
readonly.
Make sure your network configuration is right, ssh is hardened and
your ~/.ssh/authorized_keys has the right contents.
Make a directory /proto and copy /var and /home to it.
mkdir /proto
cp -rp /var /proto
cp -rp /home /proto
Now, create a template for /dev
mkdir /proto/dev
cd /proto/dev
cp /dev/MAKEDEV .
./MAKEDEV all
Now edit /etc/fstab, comment the entries for /dev, /var and /home out
and make the other entries readonly with noatime option:
4d0dfa46d94a8430.b none swap sw
4d0dfa46d94a8430.a / ffs ro,noatime 1 1
4d0dfa46d94a8430.d /usr ffs rw,wxallowed,nodev 1 2
swap /dev mfs rw,nosuid,noexec,-P=/proto/dev,-i=128,-s=4096 0 0
swap /var mfs rw,nosuid,noexec,-P=/proto/var,-s=8192 0 0
swap /home mfs rw,nosuid,noexec,-P=/proto/home,-s=8192 0 0
swap /tmp mfs rw,nosuid,noexec,-s=8192 0 0
Above, 4d0dfa46d94a8430 is the uuid of the micro SD-card.
Each of the last four lines will make a memory file system (MFS)
and, for /dev, /var and /home populate that with the corresponding
subdirectory from the /proto diretory.
Reboot and check everything works fine.
## Remounting read/write
In case you want to make some changes. install additional stuff, etc.
you can remount a partition by:
mount -uw /
In this case / gets remounted read-write.
## Harden ssh
I prefer to use public key authentication so I changed the
/etc/ssh/sshd_config.
Don't forget that at boot time, your /home directory will be
populated from the /proto directory, so put your public key not only
in ~/.ssh/authorized_keys but also in
/proto/home/<username>.ssh/<username>/authorized_keys otherwise you
will be able to log into your Beaglebone Black after the next
reboot.
## Set rc.conf.local
In the etc directory, create rc.conf.local with the following
lines:
ntpd_flags=-s
pflogd_flags=NO
smtpd_flags=NO
sndiod_flags=NO
This will set ntpd to set the time immediately after boot,
and to stop some unneeded services.
## Change ntpd.conf
There seems to be a problem with ntpd. It wouldn't set my clock.
The solution I found was to comment out some lines in ntpd.conf
This is what the file looks now:
servers pool.ntp.org
# sensor *
# constraints from "https://www.google.com"
## Packages
Normally, the packages directory at the OpenBSD-servers ends
with the architecture name. However, on ftp.eu.openbsd.org
there is a directory pub/OpenBSD/6.2/packages/arm (not arm7).
Normally, on OpenBSD systems I put the following line in
/root/.profile:
export PKG_PATHhttp://ftp.eu.openbsd.org/pub/OpenBSD/`uname -r`/packages/`uname -m`/
In this case this will not work, you have to manually change the
last part. On my Beaglebone Black I have this entry in
/root/.profile:
export PKG_PATH=http://ftp.eu.openbsd.org/pub/OpenBSD/`uname -r`/packages/arm/
In order to test this, I did a pkg_add gopher.
After installing:
# file gopher
gopher: ELF 32-bit LSB shared object, ARM, version 1
As a normal (non-root) user I started gopher, and it works :)
## Resources
The following pages where helpfull during the installation of OpenBSD
6.2 on the BeagleBone Black:
* OpenBSD on BeagleBone Black Everything I wish I knew before
installing the newly renamed armv7 port on a BeagleBone Black by
Ted Unangst: http://www.tedunangst.com/flak/post/OpenBSD-on-BeagleBone-Black
* Running OpenBSD off a USB Stick by Volker Roth:
http://www.volkerroth.com/tecn-obsd-diskless.html
* OpenBSD on Soekris by John Hart:
http://blog.spoofed.org/2007/12/openbsd-on-soekris-cheaters-guide.html
$Id: openbsd62beagleblack.txt,v 1.7 2018/01/04 14:01:03 matto Exp $