Copyright © 2006 The FreeBSD Documentation Project
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This document provides information about the NanoBSD tools, which can be used to create FreeBSD system images for embedded applications, suitable for use on a Compact Flash card (or other mass storage medium).
NanoBSD is a tool currently
developed by Poul-Henning Kamp <[email protected]>. It creates a FreeBSD system image for
embedded applications, suitable for use on a Compact Flash card
(or other mass storage medium).
It can be used to build specialized install images, designed for easy installation and maintenance of systems commonly called “computer appliances”. Computer appliances have their hardware and software bundled in the product, which means all applications are pre-installed. The appliance is plugged into an existing network and can begin working (almost) immediately.
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.
Once the image is present on the medium, it is possible to boot NanoBSD. The mass storage medium is divided into three parts by default:
Two image partitions:
code#1andcode#2.The configuration file partition, which can be mounted under the
/cfgdirectory at run time.
These partitions are normally mounted read-only.
The /etc and
/var directories are
md(4) (malloc) 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.
/etc/resolv.conf#vi /etc/resolv.conf[...]#mount /cfg#cp /etc/resolv.conf /cfg#umount /cfg
Note:
The partition containing
/cfg should be mounted
only at boot time and while overriding the configuration
files.
Keeping /cfg mounted at all times
is not a good idea, especially if the
NanoBSD system runs off a mass
storage medium that may be adversely affected by a large
number of writes to the partition (like when the filesystem
syncer flushes data to the system disks).
A NanoBSD image is built using
a simple nanobsd.sh shell script, which
can be found in the
/usr/src/tools/tools/nanobsd
The necessary commands to build 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=64kChange the current directory to the base directory of the NanoBSD build script.
Change the current directory to the place where the built images are located.
Install NanoBSD onto the storage medium.
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.
Invocation of the following command will force the
nanobsd.sh to read its configuration from
myconf.nano located in the current
directory:
#sh nanobsd.sh -c myconf.nano
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 FreeBSD even more, until it will consists 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— Name of build (used to construct the workdir names).NANO_SRC— Path to the source tree used to build the image.NANO_KERNEL— Name of kernel configuration file used to build kernel.CONF_BUILD— Options passed to thebuildworldstage of the build.CONF_INSTALL— Options passed to theinstallworldstage of the build.CONF_WORLD— Options passed to both thebuildworldand theinstallworldstage of the build.FlashDevice— Defines what type of media to use. CheckFlashDevice.subfor more details.
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=baz" > \
${NANO_WORLDDIR}/etc/foo
)
customize_cmd cust_fooA 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_sizeThere are a few default pre-defined customization functions ready for use:
cust_comconsole— Disables getty(8) on the VGA devices (the/dev/ttyv*device nodes) and enables the use of the COM1 serial port as the system console.cust_allow_ssh_root— Allowrootto login via sshd(8).cust_install_files— Installs files from thenanobsd/Filesdirectory, which contains some useful scripts for system administration.
Packages can be added to a
NanoBSD image using a custom
function. The following function will install all the
packages located in
/usr/src/tools/tools/nanobsd/packages:
install_packages () (
mkdir -p ${NANO_WORLDDIR}/packages
cp /usr/src/tools/tools/nanobsd/packages/* ${NANO_WORLDDIR}/packages
chroot ${NANO_WORLDDIR} sh -c 'cd packages; pkg_add -v *;cd ..;'
rm -rf ${NANO_WORLDDIR}/packages
)
customize_cmd install_packagesA complete example of a configuration file for building a custom NanoBSD image can be:
NANO_NAME=custom
NANO_SRC=/usr/src
NANO_KERNEL=MYKERNEL
NANO_IMAGES=2
CONF_BUILD='
WITHOUT_KLDLOAD=YES
WITHOUT_NETGRAPH=YES
WITHOUT_PAM=YES
'
CONF_INSTALL='
WITHOUT_ACPI=YES
WITHOUT_BLUETOOTH=YES
WITHOUT_FORTRAN=YES
WITHOUT_HTML=YES
WITHOUT_LPR=YES
WITHOUT_MAN=YES
WITHOUT_SENDMAIL=YES
WITHOUT_SHAREDOCS=YES
WITHOUT_EXAMPLES=YES
WITHOUT_INSTALLLIB=YES
WITHOUT_CALENDAR=YES
WITHOUT_MISC=YES
WITHOUT_SHARE=YES
'
CONF_WORLD='
WITHOUT_BIND=YES
WITHOUT_MODULES=YES
WITHOUT_KERBEROS=YES
WITHOUT_GAMES=YES
WITHOUT_RESCUE=YES
WITHOUT_LOCALES=YES
WITHOUT_SYSCONS=YES
WITHOUT_INFO=YES
'
FlashDevice SanDisk 1G
cust_nobeastie() (
touch ${NANO_WORLDDIR}/boot/loader.conf
echo "beastie_disable=\"YES\"" >> ${NANO_WORLDDIR}/boot/loader.conf
)
customize_cmd cust_comconsole
customize_cmd cust_install_files
customize_cmd cust_allow_ssh_root
customize_cmd cust_nobeastieThe update process of NanoBSD is relatively simple:
Build a new NanoBSD image, as usual.
Upload the new image into an unused partition of a running NanoBSD appliance.
The most important difference of this step from the initial NanoBSD installation is that now instead of using
_.disk.full(which contains an image of the entire disk), the_.disk.imageimage is installed (which contains an image of a single system partition).Reboot, and start the system from the newly installed partition.
If all goes well, the upgrade is finished.
If anything goes wrong, reboot back into the previous partition (which contains the old, working image), to restore system functionality as fast as possible. Fix any problems of the new build, and repeat the process.
To install new image onto the running
NanoBSD system, it is possible to
use either the updatep1 or
updatep2 script located in the
/root directory, depending from which
partition is running the current system.
According to which services are available on host serving new NanoBSD image and what type of transfer is preferred, it is possible to examine one of these three ways:
2.4.1. Using ftp(1)
If the transfer speed is in first place, use this example:
#ftp myhost get _.disk.image "| sh updatep1"
2.4.2. Using ssh(1)
If a secure transfer is preferred, consider using this example:
#ssh myhost cat _.disk.image.gz | zcat | sh updatep1
2.4.3. Using nc(1)
Try this example if the remote host is not running neither ftpd(8) or sshd(8) service:
At first, open a TCP listener on host serving the image and make it send the image to client:
myhost
#nc -l2222< _.disk.imageNote:
Make sure that the used port is not blocked to receive incoming connections from NanoBSD host by firewall.
Connect to the host serving new image and execute
updatep1script:#nc myhost2222| sh updatep1