8 .Nd building small FreeBSD disk images
12 .Op Ar config-name Op Ar site-name
16 utility is a script which produces a minimal implementation of
20 which typically fits on a small media such as a floppy disk,
21 or can be downloaded as a
22 single image file from some media such as CDROM, flash memory, or through
27 utility was originally created to build simple standalone systems
28 such as firewalls or bridges, but because of the ability to
29 cross-build images with different source trees than the one
30 in the server, it can be extremely useful to developers to
31 test their code without having to reinstall the system.
33 The boot media (historically a floppy disk, but also small
34 CDROM or USB keys) contains a boot loader and a
35 compressed kernel which includes a memory file system.
36 Depending on the media, it might also contain a number of
37 additional files, which can be updated at run time, and are
38 used to override/update those in the memory file system.
40 The system loads the kernel in the normal way, uncompresses
41 the memory file system and mounts it as root.
42 It then updates the memory
43 file system with files from the boot media (if present),
44 and executes a specialized version of
46 The boot media (floppy, etc.) is
47 required for loading only, and typically used read-only.
48 After the boot phase, the system runs entirely from RAM.
50 The following options are available (but also check the
52 script for more details).
53 The most important options for common operations are
58 .Bl -tag -width indent
61 Put the entire contents of the file system in the
62 memory file system image which is contained in the
64 This is the default behaviour, and is
65 extremely useful as the kernel itself can be loaded,
72 Clean the product of previous builds.
75 Specify a file that contains additional config commands.
77 .It Fl -floppy_size Ar size
78 Set the size of the disk image.
79 Typical values for a floppy disk are 1440 or 2880,
80 but other values can be used for other media (flash memories,
81 CDROM, network booted kernels).
82 Note that this option is overridden by the content of the
83 config files (config in the image tree, or the one
88 When used together with the
90 option, this initializes the
91 .Ao Ar SRC_PATH Ac Ns Pa /../usr
92 subtree as necessary to subsequently build
97 Generate an ISO image,
99 in addition to the disk image
103 Also build kernel modules.
104 These are not stored on the
106 image but are left available in the build directory.
109 Make the script non-interactive, skipping the initial menu
110 and proceeding with the build process without requiring user input.
112 .It Fl -no_all_in_mfs
113 Leaves files contained in the
117 image, so they can be loaded separately
118 from the kernel (and updated individually to
119 customize the image).
122 Omit /boot/loader, just rely on boot2 to load the kernel.
123 This saves some space but may have problems with kernels > 4MB.
125 .It Fl -objdir Ar directory
126 Specify a directory with the result of a previous buildworld.
127 This saves the need for an
129 call before creating an image.
131 .It Fl -src Ar SRC_PATH
132 Use the source tree at
136 This can be useful for cross-building
139 When using this option, you must also create and initialize the subtree at
140 .Ao Ar SRC_PATH Ac Ns Pa /../usr
141 with the correct header files, libraries, and tools (such as the
143 program) that are necessary for the cross-build (see the
146 The source files are unmodified by the
149 However the source tree is not completely read-only,
152 expects the kernel configuration file to be in one of
153 its subdirectories, and also the process of initializing the
155 subtree touches some parts of the source tree (this is a bug
156 in the release build scripts which might go away with time).
159 Make the script verbose, showing
160 commands to be executed and waiting for user
161 input before executing each of them.
162 Useful for debugging.
163 as a fully functional system.
166 As a result of extreme size limitations, the
168 environment differs from the normal
173 There are no dynamic libraries, and there is no directory
175 As a result, only static executables may be executed.
177 In order to reduce the size of the executables, all executables on a specific
178 floppy are joined together as a single executable built with
181 Some programs are supplied in minimalistic versions, specifically
183 a cut-down version of
187 a cut-down version of
193 sources reside in the hierarchy
194 .Pa /usr/src/release/picobsd .
195 In the following discussion, all relative path names are relative to this
198 The supported build script is
199 .Pa /usr/src/release/picobsd/build/picobsd
200 which can be run from anywhere, and relies on the
202 port to build a filesystem without requiring
204 or root privileges to mount a filesystem.
205 When run in interactive mode (the default without the
207 option), the script will let you configure the various parameters
208 used to build the PicoBSD image.
209 An image is configured
210 using the files and directories described below.
211 The base system contains a template, called
213 for historical reasons,
214 that can be used as a base for building various kinds
215 of network appliances.
217 You can define your own PicoBSD configuration, by creating a directory
218 with a name of your choice (e.g.\&
221 some of the following files and directories.
223 information on how to construct these files, look at one
226 configurations as a reference.
227 .Bl -tag -width indent
229 The kernel configuration file (required).
230 This is a mostly standard
231 kernel configuration file, possibly stripped down by removing
232 unnecessary drivers and options to reduce the kernel's size.
234 To be recognised as a
236 kernel config file, the file must also contain the line
239 below, and a matching
242 .Bd -literal -offset indent
243 #marker def_sz init MFS_inodes floppy_inodes
244 #PicoBSD 4200 init 8192 32768
245 options MD_ROOT_SIZE=4200 # same as def_sz
248 This informs the script of the size of the memory file system and
249 provides a few other details on how to build the image.
252 configuration (required).
253 It contains the list of directories containing program sources,
254 the list of binaries to be built, and the list of libraries that
258 manpage for the exact details on the syntax of this file.
260 The following issues are particularly important when dealing
266 We can pass build options to those makefiles which understand
267 that, in order to reduce the size of the programs.
268 This is achieved with a line of the form
270 .Dl "buildopts -DNO_PAM -DRELEASE_CRUNCH ..."
272 When providing the list of directories where source files are, it
273 is convenient to list the following entry first:
275 .Dl "srcdirs /usr/src/release/picobsd/tinyware"
279 versions of the programs will be found there.
283 is replaced with the full pathname of the directory where the
285 configuration resides (i.e., the one where we find
286 .Pa PICOBSD , crunch.conf ,
288 This can be useful to refer source code that resides within a
289 configuration, e.g.\&
291 .Dl "srcdirs @__CWD__@/src"
294 Shell variables, sourced by the
297 The most important variables here are:
298 .Bl -tag -width ".Va MY_DEVS"
304 Should be set to the list of devices to be created in the
306 directory of the image (it is really the argument passed to
308 so refer to that manpage for the names).
310 Size (in kilobytes) of the
316 which produces an image suitable for a standard floppy.
318 If you plan to store the image on a CDROM (e.g.\& using
321 floppy emulation), you can set
324 If you are planning to dump the image onto a hard disk
325 (either in a partition or on the whole disk), you
326 are not restricted to one of the standard floppy sizes.
327 Using a large image size per se does not waste RAM at runtime,
328 because only the files that are actually loaded from the image
329 contribute to the memory usage.
331 Contains a list of files to be imported in the floppy tree.
332 Absolute names refer to the standard file system, relative
333 names refer to the root of the source tree being used
336 You can normally use this option if you want to import
337 files such as shared libraries, or databases, without
338 having to replicate them first in your configuration
343 .It Pa floppy.tree.exclude
344 List of files from the standard floppy tree which
345 we do not want to be copied (optional).
347 Local additions to the standard floppy tree (optional).
348 The content of this subtree will be copied as-is into the
350 .It Pa floppy.tree. Ns Aq Ar site-name
351 Same as above, but site-specific (optional).
354 More information on the build process can be found in the
358 .Sh USING ALTERNATE SOURCE TREES
359 The build script can be instructed to use an alternate source tree
363 The tree that you specify must contain full sources for the kernel
364 and for all programs that you want to include in your image.
365 As an example, to cross-build the
368 using RELENG_4 sources, you can do the following:
369 .Bd -literal -offset indent
370 cd <some_empty_directory>
372 (cd FOO; cvs -d<my_repository> co -rRELENG_4 src)
373 picobsd --src FOO/src --init # this is needed only once
374 picobsd --src FOO/src -n -v bridge
377 If the build is successful, the directory
378 .Pa build_dir-bridge/
381 that can be downloaded with
383 a floppy image called
385 plus the products of the compilation in other directories.
386 If you want to modify the source tree in
388 a new image can be produced by simply running
390 .Dl "picobsd --src FOO/src -n -v bridge"
392 whereas if the change affects include files or libraries
393 you first need to update them, e.g.\& by re-running
395 .Dl "picobsd --src FOO/src --init # this is needed only once"
397 as you would normally do for any change of this kind.
398 .Sh INSTALLING PicoBSD
402 is run from a floppy disk, where it can be installed with a simple
404 .Dl "dd if=picobsd.bin of=/dev/rfd0"
406 and the floppy is ready to boot.
407 .Ss Hard Disk Install
408 The same process can be used to store the image on a hard disk
409 (entire volume or one of the slices):
410 .Bd -literal -offset indent
411 dd if=picobsd.bin of=/dev/ad2
412 dd if=picobsd.bin of=/dev/ad2s3
413 dd if=picobsd.bin of=/dev/ad2 oseek=NN
416 The first form will install the image on the entire disk, and it
417 should work in the same way as for a floppy.
419 The second form will install the image
420 on slice number 3 (which should be large enough to store the
421 contents of the image).
422 However, the process will only have success if the
423 partition does not contain a valid disklabel, otherwise the kernel will
424 likely prevent overwriting the label.
425 In this case you can use the
426 third form, replacing
428 with the actual start of the partition
429 (which you can determine using
431 Note that after saving the image to the slice, it will not yet be
435 command to properly initialize the label (do not ask why!).
436 One way to do this is
437 .Bd -literal -offset indent
438 disklabel -w ad0s2 auto
442 and from the editor enter a line corresponding to the actual partition, e.g.\&
443 if the image has 2.88MB (5760 sectors) you need to enter the following
444 line for the partition:
446 .Dl "a: 5760 0 4.2BSD 512 4096"
448 At this point the partition is bootable.
449 Note that the image size can be smaller than the slice size
450 (indicated as partition
454 can produce an ISO image named picobsd.iso,
457 emulation, so it has no size restrictions.
458 Installing means just burning a media with the file.
459 .Ss Booting From The Network
460 Yet another way to use
462 is to boot the image off the network.
463 For this purpose you should use the uncompressed kernel which is
464 available as a byproduct of the compilation.
465 Refer to the documentation
466 for network booting for more details, the
468 kernel is bootable as a standard
474 insert the floppy and reset the machine.
475 The boot procedure is similar to the
479 Booting from a floppy is normally rather slow (in the order of 1-2
480 minutes), things are much faster if you store your image on
481 a hard disk, Compact Flash, or CDROM.
485 to load the preloaded, uncompressed kernel image
486 which is a byproduct of the
490 the load time is a matter of a few seconds, even on a 10Mbit/s
495 loads the root file system from the memory file system, starts
497 and passes control to a first startup script,
499 The latter populates the
503 directories with the default files, then tries to identify the boot
504 device (floppy, hard disk partition) and possibly override the contents
505 of the root file system with files read from the boot device.
506 This allows you to store local configuration on the same media.
507 After this phase the boot device is no longer used, unless the
508 user specifically does it.
510 After this, control is transferred to a second script,
512 (which can be overridden from the boot device).
513 This script tries to associate a hostname to the system by using
514 the MAC address of the first ethernet interface as a key, and
517 Then control is passed to the main user configuration script,
519 which is supposed to override the value of a number of configuration
520 variables which have been pre-set in
521 .Pa /etc/rc.conf.defaults .
524 variable to create different configurations from the same file.
525 After taking control back,
527 completes the initializations, and as part of this
528 it configures network interfaces and optionally calls the
529 firewall configuration script,
530 .Pa /etc/rc.firewall ,
531 where the user can store his own firewall configuration.
535 runs entirely from main memory, and has no swap space, unless you
536 explicitly request it.
537 The boot device is also not used anymore after
539 takes control, again, unless you explicitly request it.
540 .Sh CONFIGURING a PicoBSD system
543 system can be configured through a few files which are read at boot
544 time, very much like a standard
547 There are, however, some minor differences to reduce the
548 number of files to store and/or customize, thus saving space.
549 Among the files to configure we have the following:
550 .Bl -tag -width indent
552 Traditionally, this file contains the IP-to-hostname mappings.
553 In addition to this, the
555 version of this file also contains
556 a mapping between Ethernet (MAC) addresses and hostnames, as follows:
557 .Bd -literal -offset indent
558 #ethertable start of the ethernet->hostname mapping
559 # mac_address hostname
560 # 00:12:34:56:78:9a pinco
565 where the line containing
567 marks the start of the table.
569 If the MAC address is not found, the script will prompt you to
570 enter a hostname and IP address for the system, and this
571 information will be stored in the
573 file (in memory) so you can simply store them on disk later.
575 Note that you can use wildcards in the address part, so a line
576 like the last one in the example will match any MAC address and
579 This file contains a number of variables which control the
580 operation of the system, such as interface configuration,
581 router setup, network service startup, etc.
582 For the exact list and meaning of these variables see
583 .Pa /etc/rc.conf.defaults .
585 It is worth mentioning that some of the variables let you
586 overwrite the contents of some files in
588 This option is available at the moment for
591 .Pa /etc/resolv.conf ,
592 whose contents are generally very short and suitable for this
594 In case you use these variables, remember to use newlines
595 as appropriate, e.g.\&
596 .Bd -literal -offset indent
597 host_conf="# this goes into /etc/host.conf
602 Although not mandatory, in this file you should only set the
603 variables indicated in
604 .Pa /etc/rc.conf.defaults ,
605 and avoid starting services which depend on having the network running.
606 This can be done at a later time: if you set
607 .Va firewall_enable Ns = Ns Qq Li YES ,
610 script will be run after configuring the network interfaces,
611 so you can set up your firewall and safely start network services or enable
612 things such as routing and bridging.
613 .It Pa /etc/rc.firewall
614 This script can be used to configure the
619 variable is set to the pathname of the firewall command,
621 contains the value set in
625 contains the name assigned to the host.
628 There is a small script called
630 which can be used to edit and/or save to disk a copy of the files
631 you have modified after booting.
632 The script takes one or more absolute pathnames, runs the
633 editor on the files passed as arguments, and then saves a
634 compressed copy of the files on the disk (mounting and
635 unmounting the latter around the operation).
637 If invoked without arguments,
640 .Pa rc.conf , rc.firewall ,
644 If one of the arguments is
646 (the directory name alone),
647 then the command saves to disk (without editing)
648 all the files in the directory for which a copy
649 already exists on disk (e.g.\& as a result of a previous update).
657 .An Andrzej Bialecki Aq abial@FreeBSD.org ,
658 with subsequent work on the scripts by
659 .An Luigi Rizzo Aq luigi@iet.unipi.it
664 .An Greg Lehey Aq grog@lemis.com .
666 Documentation is still incomplete.