NANOBSD(8) FreeBSD System Manager's Manual NANOBSD(8)
NAME
nanobsd.sh - utility used to create a FreeBSD system image suitable for
embedded applications
SYNOPSIS
nanobsd.sh [-bfhiKknqvwX] [-c config-file]
DESCRIPTION
The nanobsd.sh utility is a script which produces a minimal
implementation of FreeBSD (called NanoBSD), which typically fits on a
small media such as a Compact Flash card, or other mass storage medium.
It can be used to build specialized install images, designed for easy
installation and maintenance.
The following options are available:
-b Skip the build stages (both for kernel and
world).
-c config-file Specify the configuration file to use.
-f Skip the code slice extraction.
-h Display usage information.
-i Skip the disk image build stage.
-K Skip the installkernel stage of the build.
-k Skip the buildkernel stage of the build.
-n Do not cleanup before each build stage. This
suppresses the normal cleanup work done
before the buildworld stage and adds
-DNO_CLEAN to the make command line used for
each build stage (world and kernel).
-q Make output more quiet.
-v Make output more verbose.
-w Skip the buildworld stage of the build.
-X Make native-xtools.
The features of NanoBSD include:
• Ports and packages work as in FreeBSD. Every single
application can be installed and used in a NanoBSD image, the
same way as in FreeBSD.
• No missing functionality. If it is possible to do something
with FreeBSD, it is possible to do the same thing with NanoBSD,
unless the specific feature or features were explicitly removed
from the NanoBSD image when it was created.
• Everything is read-only at run-time. It is safe to pull the
power-plug. There is no necessity to run fsck(8) after a non-
graceful shutdown of the system.
• Easy to build and customize. Making use of just one shell
script and one configuration file it is possible to build
reduced and customized images satisfying any arbitrary set of
requirements.
NanoBSD Media Layout
The mass storage medium is divided into three parts by default (which are
normally mounted read-only):
• Two image partitions: code#1 and code#2.
• The configuration file partition, which can be mounted under
the /cfg directory at run time.
The /etc and /var directories are md(4) (malloc backed) disks.
The configuration file partition persists under the /cfg directory. It
contains files for /etc directory and is briefly mounted read-only right
after the system boot, therefore it is required to copy modified files
from /etc back to the /cfg directory if changes are expected to persist
after the system restarts.
BUILDING NanoBSD
A NanoBSD image is built using a simple nanobsd.sh shell script, which
can be found in the src/tools/tools/nanobsd directory. This script
creates a bootable image, which can be copied on the storage medium using
the dd(1) utility.
The necessary commands to build and install a NanoBSD image are:
cd /usr/src/tools/tools/nanobsd
sh nanobsd.sh
cd /usr/obj/nanobsd.full
dd if=_.disk.full of=/dev/da0 bs=64k
CUSTOMIZING NanoBSD
This is probably the most important and most interesting feature of
NanoBSD. This is also where you will be spending most of the time when
developing with NanoBSD.
Customization is done in two ways:
• Configuration options.
• Custom functions.
With configuration settings, it is possible to configure options passed
to both the buildworld and installworld stages of the NanoBSD build
process, as well as internal options passed to the main build process of
NanoBSD. Through these options it is possible to cut the system down, so
it will fit on as little as 64MB. You can use the configuration options
to trim down the system even more, until it will consist of just the
kernel and two or three files in the userland.
The configuration file consists of configuration options, which override
the default values. The most important directives are:
NANO_NAME Build name (used to construct the working
directory names).
NANO_SRC Path to the source tree used to build the image.
NANO_KERNEL Name of the kernel configuration file used to
build the kernel.
NANO_ARCH Machine processor architecture to build.
Defaults to output of uname -p.
NANO_BOOT0CFG Controls the options passed to boot0cfg(8); these
dictate boot0's behaviour.
NANO_BOOTLOADER The boot0 loader to use relative to the
NANO_WORLDDIR variable. This defaults to
boot/boot0sio and should be overridden to
boot/boot0 to provide a VGA console.
CONF_BUILD Options passed to the buildworld stage of the
build.
CONF_INSTALL Options passed to the installworld stage of the
build.
CONF_WORLD Options passed to both the buildworld and
installworld stages of the build.
FlashDevice Defines the type of media to use. Check the
FlashDevice.sub file for more details.
For more configuration options, please check the nanobsd.sh script.
To build NanoBSD image using the nanobsd.conf configuration file, use the
following command:
sh nanobsd.sh -c nanobsd.conf
It is possible to fine-tune NanoBSD using shell functions in the
configuration file. The following example illustrates the basic model of
custom functions:
cust_foo () (
echo "bar=topless" > \
${NANO_WORLDDIR}/etc/foo
)
customize_cmd cust_foo
There are a few pre-defined customization functions ready for use:
cust_comconsole Disables getty(8) on the virtual
syscons(4) or vt(4) terminals (/dev/ttyv*)
and enables the use of the first serial
port as the system console.
cust_allow_ssh_root Allow root to log in via sshd(8).
cust_install_files Installs files from the nanobsd/Files
directory, which contains some useful
scripts for system administration.
FILES
src/tools/tools/nanobsd Base directory of the NanoBSD build script.
EXAMPLES
Making persistent changes to /etc/resolv.conf:
vi /etc/resolv.conf
...
mount /cfg
cp /etc/resolv.conf /cfg
umount /cfg
A more useful example of a customization function is the following, which
changes the default size of the /etc directory from 5MB to 30MB:
cust_etc_size () (
cd ${NANO_WORLDDIR}/conf
echo 30000 > default/etc/md_size
)
customize_cmd cust_etc_size
SEE ALSO
make.conf(5), boot(8), boot0cfg(8)
HISTORY
The nanobsd.sh utility first appeared in FreeBSD 6.0.
AUTHORS
NanoBSD was developed by Poul-Henning Kamp <phk@FreeBSD.org>. This
manual page was written by Daniel Gerzo <danger@FreeBSD.org>.
FreeBSD 13.1-RELEASE-p6 May 19, 2016 FreeBSD 13.1-RELEASE-p6
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