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#1
and code#2
.
The configuration file partition, which can be mounted
under the /cfg
directory
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
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 (i.e. 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
directory. This script creates an image, which can be copied on
the storage medium using the dd(1) utility./usr
/src/tools/tools/nanobsd
The necessary commands to build a NanoBSD image are:
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
the myconf.nano
file 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 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
the installworld
stage of the build.
FlashDevice
— Defines what type of
media to use. Check the FlashDevice.sub
file for 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:
A more useful example of a customization function is the
following, which changes the default size of the
/etc
directory
from 5MB to 30MB:
There 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
— Allow
root
to login via sshd(8).
cust_install_files
—
Installs files from the
nanobsd/Files
directory, 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
:
A complete example of a configuration file for building a custom NanoBSD image can be:
The 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 the _.disk.full
file
(which contains an image of the entire disk),
the _.disk.image
image 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:
If the transfer speed is in first place, use this example:
#
ftp myhost
get _.disk.image "| sh updatep1"
If a secure transfer is preferred, consider using this example:
#
ssh myhost cat _.disk.image.gz | zcat | sh updatep1
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:
#
nc -l 2222
< _.disk.image
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
updatep1
script:
#
nc myhost 2222
| sh updatep1
This, and other documents, can be downloaded from http://ftp.FreeBSD.org/pub/FreeBSD/doc/
For questions about FreeBSD, read the
documentation before
contacting <questions@FreeBSD.org>.
For questions about this documentation, e-mail <doc@FreeBSD.org>.