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NANOBSD(8) System Manager's Manual NANOBSD(8) NAME nanobsd.sh -- create an embedded FreeBSD system image SYNOPSIS nanobsd.sh [-BbfhIiKknqvWwX] [-c config-file] DESCRIPTION The nanobsd.sh utility is a script which produces a minimal implementa- tion 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 installa- tion and maintenance. The following options are available: -B Skip the install stages (both for kernel and world). -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 Build the disk image from an existing build/in- stall. -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 installworld stage of the build. -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 applica- tion 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 explic- itly 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 re- duced 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 us- ing 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 configura- tion 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 over- ride 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 con- figuration 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 sys- tem console. cust_allow_ssh_root Allow root to log in via sshd(8). cust_install_files Installs files from the nanobsd/Files direc- tory, 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 15.0 July 14, 2025 NANOBSD(8)
NAME | SYNOPSIS | DESCRIPTION | BUILDING NanoBSD | CUSTOMIZING NanoBSD | FILES | EXAMPLES | SEE ALSO | HISTORY | AUTHORS
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