ralphs@netwinder.orginitrd capability for disk-less booting.
initrd
The NetWinder contains a 1 MB flash memory chip which holds the program code for initializing the system when first powered on. This `firmware' is responsible for such activities as turning on the video display and loading the core parts of the operating system from disk into memory. It is roughly equivalent to the BIOS on ordinary PC's.
The firmware on the NetWinder is actually a small Linux kernel, with support for hard disk and network access. The main purpose of this `minikernel' is to fetch the main kernel and to set up the root filesystem. The minikernel can load these resources from either the hard disk or from the network.
The minikernel also supports some advanced booting options: a small root
filesystem can be stored in the unused portion of the flash memory, or it
can be fetched from the network and stored into RAM. Seasoned Linux users
will recognize this as a slight variation on the standard initrd
facility.
The terms `firmware', `nettrom', and `flash memory' are used throughout the document and generally refer to the same thing, namely the contents of the flash memory chip. San Mehat wrote the firmware and called it `NeTTrom' which is where the name originated.
The firmware has a number of user-configurable parameters. These parameters are sometimes called the `firmware settings' or `nettrom settings'. Perhaps the notation should be standardized, but the wrong word slips out far too often, so you might as well accept both names.
The terms `flashing' or `burning' are used to refer to the process of reprogramming the contents of the flash memory chip. Sometimes it's called `popping' as well, though I will try to avoid that term.
This chapter describes the firmware settings that are commonly used for everyday operation of the NetWinder. The examples are written for the 2.0.X versions of the NetWinder firmware; older versions such as 1.3pl4 should be updated (consult the `Updating the firmware' chapter for details). The firmware version number is one of the first things to be displayed on the screen when the NetWinder boots up.
The firmware settings are accessed by interrupting the normal boot process when the message `Press any key to abort autoboot' is displayed. Pressing the space bar or some other key at this point will cause the firmware control prompt to appear. From this prompt, various commands can be issued to display and change firmware settings.
Alternatively, the same firmware control prompt can be accessed on the serial port. If there is no keyboard plugged into the NetWinder, then the firmware will assume `headless' operation and will redirect its output to the serial port at 19200 baud, 8 data bits, no parity. (Note: the speed has been increased to 115000 in version 2.0.8h and beyond).
The printenv command can be used to display the parameters and
their current values. The listing shows the parameter name in the first
column, the active value in the middle column, and the stored value in the
right column. The firmware actually maintains three separate sets of values
for each parameter: active, stored, and default. The active settings are
stored in RAM and apply to the current session only. The active settings
can be changed using the setenv command.
The active settings can be made permanent with the save-all
command, which copies the active parameters into the stored ones. It is
also possible to retrieve the stored values into the active ones using the
load-all command. Finally, it is possible to load factory default
values into the active parameters using the load-defaults
command.
The following examples show some typical configurations for the benefit of
those who don't want to read a long description of each setting (for all the
gory details, please see the `Command reference' chapter). All of the
examples begin with load-defaults to clean the slate, and end with
save-all to make the settings permanent. Neither of these commands
are strictly necessary, and experts may chose to leave them out. I've
included them here to ensure that the examples will work, regardless of what
state your system happens to be in.
For starters, here is how to get the machine back to the factory default
settings. This means that the kernel will be read from the file
/boot/vmlinux on /dev/hda1 (the first partition on the
hard disk), and that /dev/hda1 will also be mounted as the root
filesystem.
load-defaults
save-all
boot
(Note: the default values are not suitable for machines that have just been upgraded from a pre-2.0 version of the firmware, such as 1.3pl4. See the notes regarding older firmware in the `Upgrading firmware' section for more information).
Suppose you've compiled a new kernel, called my_new_kernel and
located in the /boot directory. To boot this new kernel, you would
use the following NeTTrom commands:
load-defaults
setenv kernfile /boot/my_new_kernel
save-all
boot
Remember that the save-all is optional - if you leave it out, the
new kernel will be loaded, but next time you reboot, the old kernel will be
loaded. When testing out new kernels for the first time, this is probably a
good feature!
Normally, the kernel and root filesystem are read from /dev/hda1,
but there is no reason why it has to be this way. Suppose that you had
downloaded a new disk image (a newer build, perhaps) and you've untarred it
to /dev/hda3. You can boot the new image as follows:
load-defaults
setenv kerndev /dev/hda3
setenv rootdev /dev/hda3
save-all
boot
It is possible to boot the NetWinder with the root disk mounted via NFS from
another server on your network. This might be useful for recovery purposes,
for example. To make this method work, the `other server' must have an IP
address and it must export a suitable filesystem for the NetWinder to boot
from. Suppose the server has an IP address of 1.2.3.4, and it is exporting
a disk image as /diskimage. The following commands will tell the
NetWinder firmware to boot from this NFS image:
load-defaults
setenv rootconfig nfs
setenv rootpath 1.2.3.4:/diskimage
In order to be able to talk on the network, the NetWinder needs to be
assigned an IP address (and a netmask). It is possible to use DHCP to
assign these addresses, but for simplicity, a static IP will be assumed.
Supposing the NetWinder has an IP address of 5.6.7.8 with a netmask of
255.255.0.0, then the NeTTrom commands would be:
setenv netconfig_eth0 flash
setenv eth0_ip 5.6.7.8/16
save-all
boot
Note that the netmask is expressed in IPv6 style - 255.0.0.0 becomes /8,
whereas 255.255.255.0 becomes /24.
This example still loads the kernel from the local hard disk, but then boots off the network via NFS. The hard disk isn't used after the kernel has been fetched.
The firmware can load its kernel from the network (as opposed to from the local hard disk). To make this work, the NetWinder needs an IP address and a netmask, and there needs to be a suitable boot server available on the network. The boot server must be able to transfer a kernel via the TFTP protocol. On the NetWinder, this boot option is enabled with the commands:
load-defaults
setenv kernconfig tftp
setenv kerntftpserver 10.11.12.13
setenv kerntftpfile /tftpboot/vmlinux-netwinder
This assumes that the boot server's IP address is 10.11.12.13 and that the
filename of the kernel on the bootserver is
/tftpboot/vmlinux-netwinder. As shown in the previous example, the
NetWinder must be assigned an IP address and a netmask so that it can
communicate over the network.
setenv netconfig_eth0 flash
setenv eth0_ip 5.6.7.8/16
save-all
boot
This sequence will fetch the kernel from the server and store it in RAM.
The system will then boot and mount the local hard disk /dev/hda1
as the root device.
The NetWinder can be booted without using the hard disk at all (or even without a hard disk installed) by combining the two previous examples. This is useful in a number of circumstances, including when you've totally trashed your hard disk :)
As in the previous examples, the IP addresses of the NFS server, NetWinder, and TFTP server will be assumed to be 1.2.3.4, 5.6.7.8, and 10.11.12.13 respectively. Quite frequently, the NFS server and TFTP server will actually be the same machine, so they would have the same IP address. For the sake of clarity, however, separate IPs are shown here.
load-defaults
setenv netconfig_eth0 flash
setenv eth0_ip 5.6.7.8/16
setenv kernconfig tftp
setenv kerntftpserver 10.11.12.13
setenv kerntftpfile /tftpboot/vmlinux-netwinder
setenv rootconfig nfs
setenv rootpath 1.2.3.4:/diskimage
save-all
boot
The first section configures the NetWinder's network interface (address and netmask), the second block arranges for the kernel to be fetched via TFTP, and the third section sets up the NFS root filesystem.
This chapter explains how to upgrade the firmware to a newer version. To determine which version of the firmware you have, watch the screen when you power up your machine. There are three major releases of firmware currently `out there': the present series (2.0.x), the old stuff (1.3), and the really old stuff (less than 1.3). Anything pre-2.0 should be updated immediately. Depending on the existing firmware version number, the process for updating will vary slightly: consult the appropriate section below.
Please note that reprogramming the firmware is an inherently dangerous activity that could potentially render your NetWinder completely inoperative. Without the firmware, a NetWinder will not be able to boot itself. Before attempting to reprogram the firmware, back up all important files and prepare yourself for the possibility of having to return your machine for repair. Needless to say, firmware upgrades are done entirely at your own risk!
In practice the flash updating process is really quite safe. Follow the directions given here and things should work out fine. If this is your first attempt to update the firmware, please read this chapter completely before you begin. If you still have problems, you can ask for help on the mailing lists or newsgroups ( news://news.netwinder.org). Statistically speaking, the likelyhood of toasting your machine is less than 1%, based on the number of units returned with dead flashes in the last year.
New versions of the firmware can be obtained anonymously from
ftp://ftp.netwinder.org/pub/netwinder/firmware/ and have filenames of
the form nettrom-X.Y.Z.bin where X.Y.Z is the version
number. Be sure to use binary mode when downloading the file. At the time
of this writing, the current stable nettrom version is 2.1.24. More recent
development versions can also be found elsewhere on the ftp site
(hint: look in Rod Stewart's or Andrew Mileski's directory), but beware that
these may not have been extensively tested - and you probably don't own JTAG
equipment (just thought I'd remind you).
Some of the nettrom binaries are available with an attached
`rescue' filesystem. Especially for those people with small hard disks in
their NetWinders, this rescue filesystem is helpful for restoring or
updating the disk image. Therefore it is recommended that you use a
nettrom+rescue image when one is available. The only times you'd
really want to use a non-rescue image is when you plan to create your own
flashroot filesystem (see the `Advanced booting' chapter for details).
You may wish to use the md5sum command to generate a checksum of
the nettrom image you've downloaded to ensure there were no errors
in the process. This is important because the flash writing program has no
way of knowing if the nettrom binary is valid or not - it simply
copies the file into the flash memory. To compute the checksum, issue the
command
md5sum nettrom-2.0.X.bin
where nettrom-2.0.X.bin should be replaced with the name of the file
you've downloaded. Very old NetWinders may not have the md5sum
program, in which case you cross your fingers and hope for the best.
Otherwise, the computed checksum should be compared against those listed in
ftp://ftp.netwinder.org/pub/netwinder/firmware/md5sums. If the
checksums don't match exactly, delete the nettrom.bin and transfer
it again. Check that your FTP client is doing a binary transfer, not an
ASCII or text transfer.
The next step is to transfer the nettrom.bin to the actual flash
memory chip. This is done using a program called flashwrite, which
in turn depends on a kernel module called nwflash.o (on older
systems, it was called flash.o). The exact process varies slightly
depending on the age of the software on your machine; consult the
appropriate sub-section.
You must be logged in as root to reprogram the flash, and should
not be running any unecessary programs at the time. The flash writing
process is very sensitive to timing and might fail if an interrupt occurs at
the wrong moment. Before you begin, it is suggested that you unplug any
network cables or peripherals, and terminate any active tasks. In other
words, the machine should be loaded as lightly as possible.
Once the flash writing process has been started, it should not be interrupted. Should an error be detected, it is important that you do not reboot the machine under any circumstances, since the contents of the flash memory are uncertain. Repeat the flash writing process until it succeeds. Consult the troubleshooting section, below, if any errors are encountered.
Recent disk images already contain all the tools necessary to update the
flash memory. Simply download a nettrom binary from the ftp site
and then run the following commands to update the flash memory:
insmod nwflash
flashwrite -base64 nettrom-2.0.X.bin 0
Replace nettrom-2.0.X.bin with the name of the nettrom file you
downloaded. By convention, the nettrom binary is normally stored
in the /boot directory but you can put it wherever you wish -
you'll have to specify the path accordingly in the flashwrite
command. Remember that once the flashwrite has started, it must complete
successfully before you reboot the machine.
Also note that the final character in the flashwrite command line
is a zero, not the letter `o'. This parameter specifies the offset from the
beginning of the flash memory - in this case, the data is being written to
the beginning of the flash.
The process for older machines is pretty similar to that of recent machines
(see preceeding section), except the nwflash driver is called
flash and it uses different major/minor numbers. The commands to
be typed are therefore:
insmod flash
flashwrite -base64 nettrom-2.0.X.bin 0
The older flash driver is more susceptible to failure, so be sure to repeat
the flashwrite command if it fails to write the whole nettrom image.
Consult the troubleshooting section below if you have any problems.
On really old machines, the flashwrite program and the
flash driver are not included, since they were changing so often at
that time. In this case, it is recommened that you download
nettrom-1.3pl4.tar.gz in addition to the nettrom-2.0.X.bin
file. The tar.gz file contains all the necessary programs for
writing the flash, along with the 1.3pl4 version of nettrom.
This old nettrom should be deleted and the 2.0.X version used
in its place:
tar zxvf nettrom-1.3pl4.tar.gz
cd nettrom-1.3pl4
rm nettrom
cp ../nettrom-2.0.X.bin nettrom.bin
Now the flash can be written in much the same manner as before. The only
difference really is that the commands are not on the normal search path, so
they must be preceded with `./' so they can be found:
./insmod flash.o
./flashwrite -base64 nettrom.bin 0
As in the case for `older machines', this version of flashwrite is not very rubust and several tries may be necessary until the entire flash image is successfully written.
Problems during the flash writing process can be attributed to either the
insmod or the flashwrite commands. Obviously, a failure
in the former command will also lead to failure of the latter. If the error
message doesn't make it clear, you can use the lsmod command to
verify what modules are loaded. If the nwflash or flash
device is not listed, then the insmod failed. Otherwise, check the
flashwrite command.
Problems with insmod fall in two categories: either the executable
cannot be found, or the flash module can't be found. In the former
case, try including the full path, ie. /sbin/insmod. Otherwise,
the problem is with the flash module. Try both flash and
nwflash as the module name. Failing that, try looking for the
flash module with a command like find /lib/modules -name
'*flash.o' and then use the resulting full path name as the module
name.
It's also possible to get an error from insmod about a kernel
version mismatch. This means that the specified flash module is
not compatible with the kernel. Check to see if any other flash
modules are available, using the find command described above. If
not, you can try using the -f flag to insmod, to force
loading of the module. If all else fails, download the
nettrom-1.3pl4.tar.gz file and consult the instructions for `Really
old machines' above.
The most common problem with flashwrite is typing in the command
incorrectly, or not specifying the name of the nettrom.bin file
correctly. If the nettrom.bin file is not in the current
directory, then the relative or absolute pathname must be specified. And
following the filename, there must be a zero (as shown in the previous
section's examples).
An error message along the lines of `Can't open /dev/flash' indicates that
either the flash module wasn't loaded correctly (you can check this
with the lsmod command), or there is a problem with the device
entries. The proper value for the device entries depends on which module
you are using: for flash the major/minor numbers are 101 and 0,
whereas for nwflash the numbers are 10 and 160. To set the device
nodes up, use the following commands, substituting the appropriate numbers
for MAJOR and MINOR, respectively.
cd /dev
rm *flash
mknod -m644 flash c MAJOR MINOR
ln -s flash nwflash
Any other errors from flashwrite indicate a real problem writing to
the flash memory. If this condition persists, try loading the flash driver
with debugging turned on: first do rmmod flash, then repeat the
insmod command with flashdebug=1 suffixed on.
Once the flashwrite program completes, the update is pretty much
done. Ensure that the number of bytes written matches the size of the
nettrom.bin file you were writing. If the numbers do not match,
repeat the flashwrite process again. Otherwise, it is safe to shut down the
machine (using CTRL-ALT-DEL for example) and upon reboot the new firmware
will be active.
If you are paranoid, you can perform one more test before you reboot. The
data can be read back from the flash memory and be compared with the
original nettrom.bin file. It's pretty unlikely for any
discrepancies to turn up, since flashwrite already performs such
checking, but it doesn't hurt either. You need to know the size in bytes of
the nettrom.bin file you just flashed.
dd if=/dev/nwflash of=actual.nettrom bs=1 count=BYTESIZE
cmp nettrom-2.0.X.bin actual.nettrom
Replace /dev/nwflash with /dev/flash if you've got an
`older' system, and substitute the actual file size for BYTESIZE.
There should be no output from the cmp command; if there is, go
back and repeat the entire flash writing process. Keep in mind that this
test only verifies that the file was written correctly to the flash, but it
cannot protect against having an invalid file in the first place.
Now it's time to perform ancient tribal rituals (or just cross your fingers) and reboot your machine. With luck, you'll see the white banner screen with the new firmware version number displayed. Shortly thereafter you should see the `Press any key to abort autoboot' message. Getting that far indicates that your flash reprogramming was successful.
The first time you boot a new version of firmware, it is a good idea to
issue the commands load-defaults followed by save-all.
If you don't do this, your old settings will be preserved, but you may see a
warning message whenever you enter the firmware menu, and it is possible for
there to be some odd side-effects.
If you've just upgraded from pre-2.0 firmware, then some special
considerations apply. The default parameters in 2.0 firmware assume that
the disk is partitioned with /dev/hda1 as the root filesystem, and
that the kernel is also contained on that partition. However, the 1.3
firmware used a different setup - /dev/hda1 was a dedicated kernel
partition, and the root filesystem resided on /dev/hda2. It is
recommeded to update to the new layout, but that is outside the scope of
this document. In order to boot the old-style layout with 2.0 firmware, the
following command sequence should be issued the first time you boot up:
load-defaults
setenv kernconfig partition
setenv rootdev /dev/hda2
save-all
boot
It is recommended that you stop using this partition-based boot method,
since it is difficult to recover from a bad kernel. If you don't want to
repartition and re-install your whole system, you can still switch to the
new boot method. Simply install a NetWinder kernel into the /boot
directory on your system and instruct the firmware to boot it:
load-defaults
setenv kernconfig fs
setenv kerndev /dev/hda2
setenv kernfile /boot/vmlinux
setenv rootdev /dev/hda2
save-all
boot
With this setup, you can install many different kernels in /boot
and switch between them by changing the kernfile parameter.
... Don't panic! In some cases you may still be able to rescue the machine. If the first 32 kB of flash are still intact, then it is possible to serially download a kernel and boot it. Then the flash memory can be reprogrammed again, hopefully with a working image this time!
A second computer is required, along with a null-modem cable. Such a cable can be had at most computer stores, or you can make your own (see the Serial-HOWTO for details). The cable should connect between the serial port on the NetWinder and the serial port on the rescue system.
Next, a terminal program should be launched on the rescue system. It should be configured for 19200 bps, 8 data bits, no parity, and 1 stop bit (For firmware 2.0.8h and beyond, the speed is 115200 bps). Be sure to turn off any handshaking, both hardware and software. Then turn on or reboot the NetWinder - a number of diagnostic messages should be printed on the serial terminal. If you see nothing, check the cables and the COM port settings. If you really don't get any output, then you flash is truly wrecked, and you'll have to return your machine for repair. Sorry.
Otherwise, you should see the message `Press * TWICE to abort autoboot' or similar. Some older versions of the firmware used ALT-D instead of an asterisk character. Press the appropriate key, and a Nettrom control menu will appear. You can press `?' for a brief listing of available commands.
The next step is to obtain a NetWinder kernel and put it on the rescue system. If you have older firmware and a 2.0 kernel, please skip down to the next sub-section for further instructions. The "z" option described below is also available in newer firmware versions, but the new "x" option is considerably nicer.
x c000
The firmware is now expecting a kernel to be transmitted in Xmodem format.
Use your terminal program to transmit the file (in minicom the command is
ALT-S). You may have to repeat the x command since it times out
after a short period.
The kernel should download in about 2 minutes at 115200 bps. Once it is
done, use the command j c000 to start the kernel. If you wish to
change the root device from the default of /dev/hda1 (major 3,
minor 1), it must be done before the "j" command. Use d 100 and
note that location 110 contains 0301. Change this to the value you want
using the e 110 command.
The official 2.0.x kernels from the ftp site cannot be used directly because
they are in ELF format - but the firmware only knows how to deal with an
a.out kernel. The vmelf utility program (
ftp://ftp.netwinder.org/pub/netwinder/kernel/misc/vmelf.c) can be
used to convert an ELF kernel into a.out form (well, close enough
anyways). Just type make vmelf to build an executable from the
vmelf.c source code. It's a hack.
Record the size of the kernel file - it will typically be somewhere between
870000 and 1250000 bytes. Convert the size from decimal into hexadecimal
(sorry, that's all the nettrom menu knows about) and write it down. Now, at
the Nettrom prompt, use the `z' command to load the kernel. The arguments
are two hexadecimal numbers - the first is always c000, and the
second should be the size in hex of the kernel file. Don't include the
`0x' or `$' symbols in the size value.
z c000 HEXSIZE
Use the `upload' feature of your terminal program to actually transmit the kernel file. Notice that the file must be transmitted `plain binary', meaning that there is no protocol (like xmodem, zmodem, or kermit). It just a raw stream of bytes. This also means there is no error checking. Note that as of firmware 2.0.8, Xmodem is supported; see above for details.
The transmission will take about 10 minutes at 19200 baud. A series of asterisks will be printed as the transfer proceeds. (Yes, there is an option to change the baud rate, but it doesn't work as you would expect. It's best just to stick with the standard rate and wait. After all you should only ever need to do this once). Upon completion of the download, the Nettrom prompt should re-appear. If there is no prompt, or there are lots of extra characters after the Nettrom prompt, then something got out-of-sync during the download. In this case, you'll probably have to repeat the whole process. But it doesn't hurt to try to boot the kernel anyhow - you might get lucky. The following command will boot the kernel:
j c000
Hopefully your machine should boot up fine now, and you can go and reprogram
the firmware properly. There is no way to pass a command line to the
kernel, so the compiled-in default values will be used. Usually the
defaults are 16 megs of RAM and a root device of /dev/hda1 - this
should boot most machines. If your setup differs, you can hack different
values into the kernel file before you send it down the serial cable.
Kernels as of 990121 use a param_struct (defined in
include/asm-arm/setup.h) for passing in the various boot-time
parameters. It is possible to modify this structure using the Nettrom
debugger commands (type `?' for help at the nettrom prompt). The
structure is stored at memory location 0x100.
In this section, the NeTTrom parameters will be explained in detail. It is
meant more as a reference guide; for most people, the examples in the `Using
the firmware' chapter should be sufficient. The parameters are grouped into
several sections that are logically connected - the same way they are listed
when the printenv command is used.
Eth0 is the 10-base-T network interface on the back of the NetWinder. If the minikernel is to do any networking (such as fetching a kernel, or booting from an NFS server), then the interface must be assigned an IP address and netmask in this section. Either static addresses or dynamic (DHCP) can be used.
The first parameter, netconfig_eth0, determines how the interface
is configured. The default setting of disk means that the
interface is not configured (inactive). A setting of flash means
that the address and netmask are specified in the eth0_ip
parameter. A setting of dhcp indicates that DHCP is to be used to
configure the interface.
...dhcp parameters should be described here...
The eth0_ip parameter contains the network address and netmask
value for the eth0 interface. The two values should be separated by a
slash, and the netmask should be expressed as a single number (IPv6 style).
This field is ignored unless netconfig_eth0 is set to
flash.
Eth1 is the 10/100-base-T network interface. It has a set of parameters that function identically to those of the eth0 interface. Consult the previous section for a full description.
These options allow the firmware to contact boot servers (TFTP and NFS) that
are not on the same subnet as the NetWinder. Issue the command setenv
route1 with no additional arguments for some examples of how to set it
up. This feature has not been widely tested.
The bootloader can load an initial ram disk out of the flash memory. One common use for this feature is to provide a `rescue' filesystem that can be used to restore the hard disk, without needing to set up an NFS server and a TFTP server.
The initrd parameter can be set to either inactive or
flash. In the latter case, the bootloader searches the flash
memory for a compressed ram disk and arranges for it to be booted as the
root device.
The other initrd options are not implemented as of this writing.
This section determines how the NetWinder will fetch its kernel. The first
parameter, kernconfig, determines which method will be used to fetch
the kernel. It can be set to one of partition, fs, or
tftp.
Normally, kernconfig is set to fs, which stands for
`filesystem'. In this case, the values of the parameters kerndev
and kernfile determine the device and name of the kernel file. The
bootloader will look on the specified device and try to load and execute the
specified filename. The file should be a valid linux kernel.
Prior to the 2.0 firmware series, the kernel was stored in raw form on a
dedicated partition (ie. without a filesystem). Support for this `legacy'
method is available by setting kernconfig to partition.
In this case, the kernel is loaded directly from the device specified by
kerndev. There is no filename. Obviously, the root device must be
on a different device in this case. Most people won't want to use this
option.
The third option is to fetch a kernel via TFTP from a server on the network.
Setting kernconfig to tftp enables this option, which also
requires that a network interface be configured (see the section above).
The ip address of the TFTP server should be stored into the
kerntftpserver parameter, and the filename (on the server) should
be stored in kerntftpfile.
The multiple file name fields are provided to make it easy to switch between
network and local booting. Once configured, only the kernconfig
parameter needs to be changed.
The rootconfig parameter specifies how the NetWinder will obtain
its root filesystem. The possible values are either disk for local
booting, and nfs for network booting.
When the rootconfig parameter is set to disk, then the
boot device specified by the rootdev parameter will be used.
Typically the root device would be /dev/hda1 or some other hard
drive partition. However, any devices that were detected at boot-up may be
legitimately specified. For example, a ZIP drive attached on the parallel
port could be used as the boot device.
Network booting is enabled by setting rootconfig to the value
nfs. The IP address and the export name for the NFS server should
be specified in the rootpath parameter (a typical example would be
10.1.2.3:/export/netwinder).
The cmdappend parameter can be used to specify additional options
to be passed to the kernel. The contents of this field will be appended to
the kernel command line, without any checking done. One common use is to
pass special arguments to the init process.
The passwd parameter can be used to password-protect the firmware
settings, to prevent unauthorized haxors (or young children) from messing
with your configuration settings.
initrdThis chapter covers the more esoteric booting options, namely those that
involve an initial ram disk (initrd). The casual user can safely
skip this chapter. The features described in this chapter are subject to
change.
To get started, an empty ram disk should be created. The following example creates an empty filesystem of about 4 MB. There are no particular restrictions on the size of the disk at this point, but making it needlessly large will just consume RAM when the machine is running later on.
dd if=/dev/zero of=myramdisk bs=1k count=4096
mke2fs -F myramdisk
insmod loop
mount -oloop myramdisk /mnt
The disk can now be populated by copying files into /mnt. Keep in
mind that for each binary, all necessary libraries and configuration files
must be installed as well. Finally, you should create a file called
/mnt/linuxrc and make it executable. This script will be run when
the disk is booted. The chroot command is helpful for testing out
the disk before installing it. Once you are satisfied, the next step is to
unmount, then compress the disk image:
umount /mnt
gzip myramdisk
This will produce a file called myramdisk.gz. There are size
restrictions on this compressed ram disk image, as explained in the next
section. If your image is too large, you'll have reduce the number of files
you put into the image.
The compressed ram disk image can either be burned into the flash memory chip, or it can be fetched via TFTP when the NetWinder boots. The first option allows for diskless, networkless booting of a NetWinder, while the second option allows a somewhat larger ram disk to be loaded.
The compressed disk image can be written to the unused portion of the flash
memory. The proceedure is to simply join the compressed image on to the end
of a standard nettrom binary image, and then to write the combined
image into the flash memory:
cat nettrom-2.0.X.bin myramdisk.gz >combined.img
insmod nwflash
flashwrite -base64 combined.img 0
NetWinders normally have 1 MB of flash memory, with the top 64 kB reserved
for configuration data. The total size of `combined.img' must not
exceed 983040 bytes (that's 1 MB minus 64 kB), otherwise it won't work (and
if you were expecting a little warning message to be printed if you exceed
the size, guess again...)
To try out the image, reboot the NetWinder and go into the firmware control
menu. Issue the command setenv initrd flash, save the parameters
if you wish, and boot it. If you've done things correctly, your ram disk
will be loaded and the linuxrc script will be run.
A somewhat larger initial ram disk can be loaded via TFTP protocol over the network. This option is only available with version 2.0.7 of the NetWinder firmware. The compressed ram disk should be concatenated onto a normal NetWinder kernel. The maximum allowable size of the combined kernel and compressed filesystem is 4 MB (ie. 4194304 bytes). Please note that at this time, only ELF kernels (ie. most 2.0.35 kernels) will work - the 2.2 kernel series are not recognized as ELF and the ramdisk won't be detected. This will be fixed in an upcoming nettrom.
cat /boot/vmlinux myramdisk.gz >vmlinux+ramdisk
The resulting file vmlinux+ramdisk should be transfered to the TFTP
server machine, perhaps via ftp or nfs. The NetWinder should then be
rebooted and the firmware settings for TFTP booting should be activated:
setenv kernconfig tftp
setenv kerntftpserver 10.2.3.4
setenv kerntftpfile vmlinux+ramdisk
Of course the IP address and filename will need to be adjusted for your particular setup. For more details, consult the TFTP example in the `Using the firmware' chapter.
It is possible to download a kernel via the serial port. This is intended for emergency situations only where the flash memory doesn't contain a valid boot image. See the last section in the `Updating the firmware' chapter for details.
The author and maintainer of the NetWinder Firmware-HOWTO is Ralph Siemsen (ralphs@netwinder.org). Please send me any comments, additions, corrections so that the can be included in the next release. The latest version of this document can be obtained from http://www.netwinder.org/~ralphs/howto/Firmware-HOWTO.html.
The descriptions of some of the boot options in the `Reference' chapter are lacking. These are the options that I don't normally use, and so I don't have much to say about. To be fixed.
The `sgml2info' version of this document doesn't show the examples properly - for some reason the linefeeds are removed. Why is this and how do I fix it?
April 20, 1999 (version 1.5): First public release of this document.
April 25, 1999 (version 1.6): Suggested by Woody: Added section on what to do if serial downloading doesn't complete, added note about param_struct at 0x100, and suggested installing new kernel if upgrading from pre-2.0 firmware.
April 26, 1999 (version 1.7): In tftp+initrd section, mention that ELF kernel must be used (and 2.2 currenty doesn't work). Thanks to Jim Studt for bringing this to my attention.
Sep 3, 1999 (version 1.8): Fixed URL's on the ftp site from pub/ccc
to the new pub/netwinder. Added xmodem info in the serial kernel
recovery section.
Dec 3, 2001 (version 1.9): Corrected error in ln -s flash nwflash
example in section 3.4 (thanks to Ron Golan for catching this).
San Mehat (nettwerk@netwinder.org) wrote the original firmware and wrote the preliminary documentation for it.
Woody Suwalski (woody@netwinder.org) maintained the firmware up until version 2.3, and reviewed this documentation.
Andrew Mileski (andrewm@netwinder.org) added in initrd support for
tftp'ed kernels in version 2.0.7 of the firmware.
This document is copyright (c) Ralph Siemsen, 1999.
Permission is granted to make and distribute copies of this manual provided the copyright notice and this permission notice are preserved on all copies.
There is no warrantee whatsoever.