SRM Firmware Howto

SRM Firmware Howto
Rich Payne <mailto:[email protected]>, and David Huggins-
Daines <mailto:[email protected]>
v0.6.1, 5 March 2000

This document describes how to boot Linux/Alpha using the SRM console,
which is the console firmware also used to boot Compaq Tru64 Unix
(also known as Digital Unix and OSF/1) and OpenVMS.
______________________________________________________________________

Table of Contents

1. About this manual

1.1 Who should read this manual
1.2 Conventions

2. What is SRM?

2.1 Getting to SRM
2.2 Using the SRM console
2.3 How Does SRM Boot an OS?
2.4 Loading The Secondary Bootstrap Loader

3. The Raw Loader

4. The aboot Loader

4.1 Getting and Building aboot
4.2 Floppy Installation
4.3 Harddisk Installation
4.4 CD-ROM Installation
4.5 Building the Linux Kernel
4.6 Booting Linux
4.6.1 Device Naming
4.6.2 Boot Filename
4.6.3 Boot Flags
4.6.4 Using aboot interactively
4.6.5 The aboot.conf configuration file
4.6.5.1 Selecting the Partition of /etc/aboot.conf
4.7 Booting Over the Network
4.8 Partitioning Disks
4.8.1 What is a disklabel?
4.8.2 Partitioning the Easy Way: a DOS Disklabel
4.8.3 Partitioning with a BSD Disklabel

5. Sharing a Disk With DEC Unix

5.1 Partitioning the disk
5.2 Installing

6. Installation of Distributions

6.1 RedHat 6.0 and 6.1
6.1.1 Installation from the Red Hat 6.0 or 6.1 CD
6.2 SuSE 6.1
6.2.1 Installation from the SuSE 6.1 CD
6.3 SuSE 6.3
6.3.1 Installation from the SuSE 6.3 CD

7. Document History

______________________________________________________________________

1. About this manual

1.1. Who should read this manual

You should read this manual if you are installing Linux on a new Alpha
system that can only boot from the SRM console, or if you are
installing Linux on an older Alpha system that can use the SRM console
and wish to use SRM to boot your Linux installation.

Because SRM is the only way to boot Linux on modern Alpha systems, and
because it provides the proper operating environment for Unix and
Unix-like operating systems (such as Linux), it is the recommended way
of booting Linux on Alpha when available.

Sometimes, it is preferable to use the ARC, ARCSBIOS, or AlphaBIOS
console, such as if you have a machine for which SRM is not available,
if you wish to dual-boot with Windows NT without switching consoles,
or if you have hardware that is not supported by SRM. On these
machines, you will typically use MILO to boot Linux. For more
information, refer to the MILO Howto, available from
http://www.alphalinux.org/faq/milo.html
<http://www.alphalinux.org/faq/milo.html>.

1.2. Conventions

Throughout this manual, we will use the following conventions for
commands to be entered by the user:

SRM console commands will be shown with the characteristic SRM will
see 'P00>' instead, or possibly some other number depending on which
processor SRM is running.--)

>>> boot dva0 -fi linux.gz -fl "root=/dev/fd0 load_ramdisk=1"

Unix commands will be shown with the '#' command prompt if they are to
be run as root, or '$' if they are to be run by a normal user, like
this:

# swriteboot -f3 /dev/sda /boot/bootlx

Aboot commands will be shown with the 'aboot>' command prompt, like
this:

aboot> b 6/boot/vmlinuz root=/dev/hda6

2. What is SRM?

SRM console is used by Alpha systems as Unix-style boot firmware.
Tru64 Unix and OpenVMS depend on it and Linux can boot from it. You
can recognize SRM console as a blue screen with a prompt that is
presented to you on power-up.
2.1. Getting to SRM

Most Alpha systems have both the SRM and ARC/AlphaBIOS console in
their firmware. On one of these machines, if your machine starts up
with ARC/AlphaBIOS by default, you can switch to SRM through the
"Console Selection" option in the Advanced CMOS Setup menu. To make
the change permanent, you should set the os_type environment variable
in SRM to "OpenVMS" or "Unix", like this:

>>> set os_type Unix

Either one will work to boot Linux. However, if you intend to dual-
boot OpenVMS on this machine, you must set os_type to "OpenVMS".
Conversely, to return to ARC/AlphaBIOS, you can set os_type to "NT".

Some older systems may not have both SRM and ARC in firmware as
shipped. On these systems, you will have to upgrade your firmware.
See <http://ftp.digital.com/pub/DEC/Alpha/firmware/> for the latest
firmware updates and instructions.

A few older systems (primarily evaluation boards such as the 164SX and
164LX) are "half-flash" systems, whose firmware can hold SRM or
AlphaBIOS, but not both. If you have one of these machines, you will
have to reflash your firmware with the SRM console using the AlphaBIOS
firmware update utility. Again, see
<http://ftp.digital.com/pub/DEC/Alpha/firmware/> for firmware images
and instructions. If you wish to return to AlphaBIOS on these
machines, you may rerun the firmware update utility from a floppy in
SRM using the fwupdate command. You can also start AlphaBIOS from a
floppy using the arc command.

2.2. Using the SRM console

The SRM console works very much like a Unix or OpenVMS shell. It
views your NVRAM and devices as a pseudo-filesystem. You can see this
if you use the ls command. Also, it contains a fairly large set of
diagnostic, setup, and debugging utilities, the details of which are
beyond the scope of this document. As in the Unix shell, you can pipe
the output of one command to the input of another, and there is a more
command that works not unlike the Unix one. To get a full listing of
available commands, run:

>>> help | more

As well, SRM has environment variables, a number of which are pre-
defined and correspond to locations in NVRAM. You can view the entire
list of environment variables and their values with the show command
(there are quite a few of them, so you will probably want to pipe its
output to more). You can also show variables matching a "glob"
pattern - for example, show boot* will show all the variables starting
in "boot".

Environment variables are categorized as either read-only, warm non-
volatile, or cold non-volatile. The full listing of pre-defined
variables is detailed in the Alpha Architecture Reference Manual. The
most useful pre-defined environment variables for the purposes of
booting Linux are bootdef_dev, boot_file, boot_flags, and auto_action,
all of which are cold non-volatile.
To set environment variables, use the set command, like this:

>>> set bootdef_def dka0

If you set an undefined variable, it will be created for you, however
it will not persist across reboots.

The bootdef_dev variable specifies the device (using VMS naming
conventions - see ``'' for an explanation of these) which will be
booted from if no device is specified on the boot command line, or in
an automatic boot. The boot_file variable contains the filename to be
loaded by the secondary bootloader, while boot_flags contains any
extra flags. auto_action specifies the action which the console
should take on power-up. By default, it is set to HALT, meaning that
the machine will start up in the SRM console. Once you have
configured your bootloader and the boot-related variables, you can set
it to BOOT in order to boot automatically on power-up.

Finally, two helpful console keystrokes you should know are Control-C,
which, as in the shell, halts a command in progress (such as an
automatic boot), and Control-P, which if issued from the aboot prompt
(or other secondary bootloader) will halt the bootloader and return
you to the SRM console.

2.3. How Does SRM Boot an OS?

All versions of SRM can boot from SCSI disks and the versions for
recent platforms, such as the Noname or AlphaStations can boot from
floppy disks as well. Network booting via bootp is supported. Note
that older SRM versions (notably the one for the Jensen) cannot boot
from floppy disks. Booting from IDE devices is supported on newer
platforms (DS20, DS10, DP264, UP2000 etc..).

Booting Linux with SRM is a two step process: first, SRM loads and
transfers control to the secondary bootstrap loader. Then the
secondary bootstrap loader sets up the environment for Linux, reads
the kernel image from a disk filesystem and finally transfers control
to Linux.

Currently, there are two secondary bootstrap loaders for Linux: the
raw loader that comes with the Linux kernel and aboot which is
distributed separately. These two loaders are described in more
detail below.

2.4. Loading The Secondary Bootstrap Loader

SRM knows nothing about filesystems or disk-partitions. It simply
expects that the secondary bootstrap loader occupies a consecutive
range of physical disk sector, starting from a given offset. The
information on the size of the secondary bootstrap loader and the
offset of its first disk sector is stored in the first 512 byte
sector. Specifically, the long integer at offset 480 stores the size
of the secondary bootstrap loader (in 512-byte blocks) and the long at
offset 488 gives the sector number at which the secondary bootstrap
loader starts. The first sector also stores a flag-word at offset 496
which is always 0 and a checksum at offset 504. The checksum is
simply the sum of the first 63 long integers in the first sector.

If the checksum in the first sector is correct, SRM goes ahead and
reads the size sectors starting from the sector given in the sector
number field and places them in virtual memory at address 0x20000000.
If the reading completes successfully, SRM performs a jump to address
0x20000000.

3. The Raw Loader

The sources for this loader can be found in directory arch/alpha/boot
of the Linux kernel source distribution. It loads the Linux kernel by
reading START_SIZE bytes starting at disk offset BOOT_SIZE+512 (also
in bytes). The constants START_SIZE and BOOT_SIZE are defined in
linux/include/asm-alpha/system.h. START_SIZE must be at least as big
as the kernel image (i.e., the size of the .text, .data, and .bss
segments). Similarly, BOOT_SIZE must be at least as big as the image
of the raw bootstrap loader. Both constants should be an integer
multiple of the sector size, which is 512 bytes. The default values
are currently 2MB for START_SIZE and 16KB for BOOT_SIZE. Note that if
you want to boot from a 1.44MB floppy disk, you have to reduce
START_SIZE to 1400KB and make sure that the kernel you want to boot is
no bigger than that.

To build a raw loader, simply type make rawboot in the top directory
of your linux source tree (typically /usr/src/linux). This should
produce the following files in arch/alpha/boot:

tools/lxboot:
The first sector on the disk. It contains the offset and size
of the next file in the format described above.

tools/bootlx:
The raw boot loader that will load the file below.

vmlinux.nh:
The raw kernel image consisting of the .text, .data, and .bss
segments of the object file in /usr/src/linux/vmlinux. The
extension .nh indicates that this file has no object-file
header.

The concatenation of these three files should be written to the disk
from which you want to boot. For example, to boot from a floppy,
insert an empty floppy disk in, say, /dev/fd0 and then type:

# cat tools/lxboot tools/bootlx vmlinux >/dev/fd0

You can then shutdown the system and boot from the floppy by issuing
the command boot dva0.

4. The aboot Loader

When using the SRM firmware, aboot is the preferred way of booting
Linux. It supports:

o direct booting from various filesystems (ext2, ISO9660, and UFS,
the DEC Unix filesystem)

o listing directories and following symbolic links on ext2 (version
0.6 and later)

o booting of executable object files (both ELF and ECOFF)

o booting compressed kernels

o network booting (using bootp)

o partition tables in DEC Unix format (which is compatible with BSD
Unix partition tables)

o interactive booting and default configurations for SRM consoles
that cannot pass long option strings

4.1. Getting and Building aboot

The latest sources for aboot are available in this ftp directory
<ftp://ftp.alphalinux.org/pub/aboot>. The description in this manual
applies to aboot version 0.6 or newer. Please note that many
distributions ship aboot with them so downloading aboot from this
directory is probably unnessesary.

Once you downloaded and extracted the latest tar file, take a look at
the README and INSTALL files for installation hints. In particular,
be sure to adjust the variables in Makefile and in include/config.h to
match your environment. Normally, you won't need to change anything
when building under Linux, but it is always a good idea to double
check. If you're satisfied with the configuration, simply type make
to build it (if you're not building under Linux, be advised that aboot
requires GNU make).

After running make, the aboot directory should contain the following
files:

aboot
This is the actual aboot executable (either an ECOFF or ELF
object file).

bootlx
Same as above, but it contains only the text, data and bss
segments---that is, this file is not an object file.

sdisklabel/writeboot
Utility to install aboot on a hard disk.

tools/e2writeboot
Utility to install aboot on an ext2 filesystem (usually used for
floppies only).

tools/isomarkboot
Utility to install aboot on a iso9660 filesystem (used by CD-ROM
distributors).

tools/abootconf
Utility to configure an installed aboot.

4.2. Floppy Installation

The bootloader can be installed on a floppy using the e2writeboot
command (note: this can't be done on a Jensen since its firmware does
not support booting from floppy). This command requires that the disk
is not overly fragmented as it needs to find enough contiguous file
blocks to store the entire aboot image (currently about 90KB). If
e2writeboot fails because of this, reformat the floppy and try again
(e.g., with fdformat(1)). For example, the following steps install
aboot on floppy disk assuming the floppy is in drive /dev/fd0:

# fdformat /dev/fd0
# mke2fs /dev/fd0
# e2writeboot /dev/fd0 bootlx

4.3. Harddisk Installation

Since the e2writeboot command may fail on highly fragmented disks and
since reformatting a harddisk is not without pain, it is generally
safer to install aboot on a harddisk using the swriteboot command.
swriteboot requires that the first few sectors are reserved for
booting purposes. We suggest that the disk be partitioned such that
the first partition starts at an offset of 2048 sectors. This leaves
1MB of space for storing aboot. On a properly partitioned disk, it is
then possible to install aboot as follows (assuming the disk is
/dev/sda):

# swriteboot /dev/sda bootlx

On systems where partition c in the entire disk it will be necessary
to 'force' the write of aboot. In this case use the -f flag followed
by the partition number (in the case of partition c this is 3):

# swriteboot /dev/sda bootlx -f3

On a Jensen, you will want to leave some more space, since you need to
write a kernel to this place, too---2MB should be sufficient when
using compressed kernels. Use swriteboot as described in Section ``''
to write bootlx together with the Linux kernel.

4.4. CD-ROM Installation

To make a CD-ROM bootable by SRM, simply build aboot as described
above. Then, make sure that the bootlx file is present on the iso9660
filesystem (e.g., copy bootlx to the directory that is the filesystem
master, then run mkisofs on that directory). After that, all that
remains to be done is to mark the filesystem as SRM bootable. This is
achieved with a command of the form:

# isomarkboot filesystem bootlx

The command above assumes that filesystem is a file containing the
iso9660 filesystem and that bootlx has been copied into the root
directory of that filesystem. That's it!

4.5. Building the Linux Kernel

A bootable Linux kernel can be built with the following steps. During
the make config, be sure to answer "yes" to the question whether you
want to boot the kernel via SRM (for certain platforms this is
automatically selected). Note that if you build a generic kernel (by
selecting "Generic" as the alpha system type), the kernel is able to
guess whether it is running under SRM or not.

# cd /usr/src/linux
# make config
# make dep
# make boot
# make modules (if applicable)
# make modules_install (if applicable)

The last command will build the file arch/alpha/boot/vmlinux.gz which
can then be copied to the disk from which you want to boot from. In
our floppy disk example above, this would entail:

# mount /dev/fd0 /mnt
# cp arch/alpha/boot/vmlinux.gz /mnt
# umount /mnt

4.6. Booting Linux

With the SRM firmware and aboot installed, Linux is generally booted
with a command of the form:

boot devicename -fi filename -fl flags

The filename and flags arguments are optional. If they are not
specified, SRM uses the default values stored in environment variables
BOOTDEF_DEV , BOOT_OSFILE and BOOT_OSFLAGS. The syntax and meaning of
these two arguments is described in more detail below. To list the
current values of these variables type show boot* at the SRM command
prompt. This will also show a boot_dev variable (among others), this
variable is read only and needs to be changed via the bootdef_dev
variable.

4.6.1. Device Naming

This corresponds to the device from which SRM will attempt to boot.
Examples include:

dva0
- First floppy drive, /dev/fd0 under Linux

dqa0
- Primary IDE cdrom or hard disk as Master, /dev/hda under Linux

dqa1
- Primary IDE cdrom or hard disk as Slave, /dev/hdb under Linux

dka0
- SCSI disk on first bus, Device 0, /dev/sda under Linux

ewa0
- First Ethernet Device, /dev/eth0 under Linux

For example to boot from the disk at SCSI id 6, you would enter:

>>> boot dka600

To list the devices currently installed in the system type show dev at
the SRM command line. In contrast to Linux device naming, the
partition number on a disk device is not given as part of the device
name (you may see extra numbers after the device names when running
show dev - these correspond to things like PCI bus and device numbers
and are not useful to the user). Remember, as mentioned in ``'', that
SRM knows nothing about partitions or disklabels - it merely reads a
boot block and secondary bootstrap from sectors on a disk. Therefore,
the partition number is given as part of the boot filename.

4.6.2. Boot Filename

The filename argument takes the form:

[n/]filename

n is a single digit in the range 1..8 that gives the partition number
from which to boot from. filename is the path of the file you want
boot. For example to boot a kernel named vmlinux.gz from the second
partition of SCSI device 6, you would enter:

>>> boot dka600 -file 2/vmlinux.gz

Or to boot from floppy drive 0, you'd enter:

>>> boot dva0 -file vmlinux.gz

If a disk has no partition table, aboot pretends the disk contains one
ext2 partition starting at the first diskblock. This allows booting
from floppy disks.

As a special case, partition number 0 is used to request booting from
a disk that does not (yet) contain a file system. When specifying
"partition" number 0, aboot assumes that the Linux kernel is stored
right behind the aboot image. Such a layout can be achieved with the
swriteboot command. For example, to setup a filesystem-less boot from
/dev/sda, one could use the command:

# swriteboot /dev/sda bootlx vmlinux.gz

Booting a system in this way is not normally necessary. The reason
this feature exists is to make it possible to get Linux installed on a
systems that can't boot from a floppy disk (e.g., the Jensen).

4.6.3. Boot Flags

A number of bootflags can be specified. The syntax is:

-flags "options..."

Where "options..." is any combination the following options (separated
by blanks). There are many more bootoptions, depending on what
drivers your kernel has installed. The options listed below are
therefore just examples to illustrate the general idea:

load_ramdisk=1
Copy root file system from a (floppy) disk to the RAM disk
before starting the system. The RAM disk will be used in lieu
of the root device. This is useful to bootstrap Linux on a
system with only one floppy drive.

floppy=str
Sets floppy configuration to str.

root=dev
Select device dev as the root-file system. The device can be
specified as a major/minor hex number (e.g., 0x802 for
/dev/sda2) or one of a few canonical names (e.g., /dev/fd0,
/dev/sda2).

single
Boot system in single user mode.

kgdb
Enable kernel-gdb (works only if CONFIG_KGDB is enabled; a
second Alpha system needs to be connected over the serial port
in order to make this work)

Some SRM implementations (e.g., the one for the Jensen) are
handicapped and allow only short option strings (e.g., at most 8
characters). In such a case, aboot can be booted with the single-
character boot flag "i". With this flag, aboot will enter interactive
mode

4.6.4. Using aboot interactively

As of version 0.6, aboot supports a simple command-oriented
interactive mode. Note that this is different from the prompt which
previous versions issued when booted with the "i" flag, or after
failing to load a kernel. You can get a summary of the available
commands by typing "h" or "?" at the prompt:

>>> boot dka0 -fl i
aboot> ?
h, ? Display this message
q Halt the system and return to SRM
p 1-8 Look in partition <num> for configuration/kernel
l List pre-configured kernels
d <dir> List directory <dir> in current filesystem
b <file> <args> Boot kernel in <file> (- for raw boot)
with arguments <args>
0-9 Boot pre-configuration 0-9 (list with 'l')
aboot> b 3/vmlinux.gz root=/dev/sda3 single

4.6.5. The aboot.conf configuration file

Since booting in that manner quickly becomes tedious, aboot allows to
define short-hands for frequently used command lines. In particular,
a single digit option (0-9) requests that aboot uses the corresponding
option string stored in file /etc/aboot.conf. A sample aboot.conf is
shown below:

#
# aboot default configurations
#
0:3/vmlinux.gz root=/dev/sda3
1:3/vmlinux.gz root=/dev/sda3 single
2:3/vmlinux.new.gz root=/dev/sda3
3:3/vmlinux root=/dev/sda3
8:- root=/dev/sda3 # fs-less boot of raw kernel
9:0/vmlinux.gz root=/dev/sda3 # fs-less boot of (compressed) ECOFF kernel
-

With this configuration file, the command

>>> boot dka0 -fl 1

corresponds exactly to the boot command shown above.

Finally, at the aboot prompt, it is possible to enter one of the
single character flags ("0"-"9") to get the same effect as if that
flag had been specified in the boot command line. As noted in the
help text cited above, you can also list the available default
configurations with the "l" command.

4.6.5.1. Selecting the Partition of /etc/aboot.conf

When installed on a harddisk, aboot needs to know what partition to
search for the /etc/aboot.conf file. A newly compiled aboot will
search the second partition (e.g., /dev/sda2). Since it would be
inconvenient to have to recompile aboot just to change the partition
number, abootconf allows to directly modify an installed aboot.
Specifically, if you want to change aboot to use the third partition
on disk /dev/sda, you'd use the command:

# abootconf /dev/sda 3

You can verify the current setting by simply omitting the partition
number. That is: abootconf /dev/sda will print the currently selected
partition number. Note that aboot does have to be installed already
for this command to succeed. As of version 0.6, swriteboot will
preserve the existing configuration when installing a new aboot on a
hard disk.

Since aboot version 0.5, it is also possible to select the aboot.conf
partition via the boot command line. This can be done with a command
line of the form a:b where a is the partition that holds
/etc/aboot.conf and b is a single-letter option as described above
(0-9, i, or h). For example, if you type boot -fl "3:h" dka100 the
system boots from SCSI ID 1, loads /etc/aboot.conf from the third
partition, prints its contents on the screen and waits for you to
enter the boot options.

4.7. Booting Over the Network

Three steps are necessary before Linux can be booted via a network.
First you need an Ethernet adapter that is supported by SRM. Most
version of SRM support the DE500 series of cards, with newer versions
(5.6 and later) also supporting the Intel EtherExpress/Pro series of
cards. Second, you need to set the SRM environment variables to
enable booting via the bootp protocol and third you need to setup
another machine as the your boot server. Enabling bootp in SRM is
usually done by setting the ewa0_protocol (DE500 cards) or
eia0_protocol (Intel cards) variable to bootp.

>>> set ewa0_protocol bootp

Setting up the boot server is obviously dependent on what operating
system that machine is running, but typically it involves starting the
program bootpd in the background after configuring the /etc/bootptab
file. The bootptab file has one entry describing each client that is
allowed to boot from the server. For example, if you want to boot the
machine myhost.cs.arizona.edu, then an entry of the following form
would be needed:

myhost.cs.arizona.edu:\
:hd=/remote/:bf=vmlinux.bootp:\
:ht=ethernet:ha=08012B1C51F8:hn:vm=rfc1048:\
:ip=192.12.69.254:bs=auto:

This entry assumes that the machine's Ethernet address is 08012B1C51F8
and that its IP address is 192.12.69.254. The Ethernet address can be
found with the show device command of the SRM console or, if Linux is
running, with the ifconfig command. The entry also defines that if
the client does not specify otherwise, the file that will be booted is
vmlinux.bootp in directory /remote. For more information on
configuring bootpd, please refer to its man page.

Next, build aboot with with the command make netboot. Make sure the
kernel that you want to boot has been built already. By default, the
aboot Makefile uses the kernel in
/usr/src/linux/arch/alpha/boot/vmlinux.gz (edit the Makefile if you
want to use a different path). The result of make netboot is a file
called vmlinux.bootp which contains aboot and the Linux kernel, ready
for network booting.

Finally, copy vmlinux.bootp to the bootserver's directory. In the
example above, you'd copy it into /remote/vmlinux.bootp. Next, power
up the client machine and boot it, specifying the Ethernet adapter as
the boot device. Typically, SRM calls the first Ethernet adapter
ewa0, so to boot from that device, you'd use the command:

>>> boot ewa0

The -fi and -fl options can be used as usual. In particular, you can
ask aboot to prompt for Linux kernel arguments by specifying the
option -fl i.

4.8. Partitioning Disks

4.8.1. What is a disklabel?

A disk label is a partition table. Unfortunately, there are several
formats the partition table can take, depending on the operating
system.

DOS partition tables are the standard used by Linux and Windows.
AlphaBIOS systems and every Linux kernel can read DOS partition
tables. Unfortunately, the SRM console's boot sector format overlaps
with parts of the DOS partition table on disk, and therefore DOS
partition tables cannot be used with SRM.

BSD disklabels are used by several variants of Unix, including Tru64.
SRM's boot block does not conflict with the BSD disklabel (in fact,
the BSD disklabel resides entirely within "reserved" areas of the
first sector), and Linux can use a BSD disklabel, provided that
support for BSD disklabels has been compiled into the kernel.

To boot from a disk using SRM, a BSD disklabel is required. If the
disk is not a boot disk, the BSD disklabel is not required. A BSD
disklabel can be created using fdisk, the standard Linux disk
partitioning tool.

4.8.2. Partitioning the Easy Way: a DOS Disklabel

The simplest way to partition your disk is to let your Linux installer
do it for you, for example by using Red Hat's disk druid or fdisk. On
Red Hat 6.1, this will produce a valid BSD disklabel, but only if the
disk in question previously contained one. In most cases, this will
produce a DOS disklabel. It will be readable by Linux, but you will
not be able to boot from it via SRM. For this reason, you will
probably want to create a BSD disklabel manually in order to boot
Linux

4.8.3. Partitioning with a BSD Disklabel

1. Start fdisk on the disk you're configuring

2. Choose to make a BSD disklabel - option 'b' (newer versions of
fdisk will detect existing BSD disklabels and automatically enter
disklabel mode)

3. You'll notice some things: Partitions are letters instead of
numbers, from a-h Partition 'c' covers the whole of the disk. This
is the convention, don't touch it. While you can see it, note down
the disk parameters as you'll use them more often than with the
DOS-disklabel approach

4. Creating a new partition uses the same procedure as the DOS-
disklabel approach, except that the partitions are referred to by
letter instead of number. That is, 'n' to make a new partition
followed by the partition letter followed by the starting block
followed by the end block

5. Setting partition type is slightly different, because the numbering
scheme is different (1 is swap, 8 is ext2).

6. When you are finished, write ('w') and quit ('q') as normal.

There are some important catches that you must be aware of when
partitioning using a BSD disklabel:

o Partition 'a' should start about 1M into the disk: don't start it
at sector 1, try starting at sector 10 (for example). This leaves
plenty of space for writing the boot block (see below)

o There is a bug in some versions of fdisk which makes the disk look
one sector bigger than it actually is. The listing when you create
the BSD disklabel is correct. The last sector of partition 'c' is
correct. The default last sector when creating a new partition is
1 sector too big

o Always adjust for this extra sector. This bug exists in the version
of fdisk shipped with Red Hat 6.0. Not making an adjustment for
this problem almost always leads to "Access beyond end of device"
errors from the Linux kernel.

Once you have made a BSD disklabel, continue the installation. After
installation, you can write a boot block to your disk to make it
bootable from SRM.

5. Sharing a Disk With DEC Unix

Unfortunately, DEC Unix doesn't know anything about Linux, so sharing
a single disk between the two OSes is not entirely trivial. However,
it is not a difficult task if you heed the tips in this section. The
section assumes you are using aboot version 0.5 or newer.

5.1. Partitioning the disk

First and foremost: never use any of the Linux partitioning programs
(minlabel or fdisk) on a disk that is also used by DEC Unix. The
Linux minlabel program uses the same partition table format as DEC
Unix disklabel, but there are some incompatibilities in the data that
minlabel fills in, so DEC Unix will simply refuse to accept a
partition table generated by minlabel. To setup a Linux ext2
partition under DEC Unix, you'll have to change the disktab entry for
your disk. For the purpose of this discussion, let's assume that you
have an rz26 disk (a common 1GB drive) on which you want to install
Linux. The disktab entry under DEC Unix v3.2 looks like this (see
file /etc/disktab):

rz26|RZ26|DEC RZ26 Winchester:\
:ty=winchester:dt=SCSI:ns#57:nt#14:nc#2570:\
:oa#0:pa#131072:ba#8192:fa#1024:\
:ob#131072:pb#262144:bb#8192:fb#1024:\
:oc#0:pc#2050860:bc#8192:fc#1024:\
:od#393216:pd#552548:bd#8192:fd#1024:\
:oe#945764:pe#552548:be#8192:fe#1024:\
:of#1498312:pf#552548:bf#8192:ff#1024:\
:og#393216:pg#819200:bg#8192:fg#1024:\
:oh#1212416:ph#838444:bh#8192:fh#1024:

The interesting fields here are o?, and p?, where ? is a letter in the
range a-h (first through 8-th partition). The o value gives the
starting offset of the partition (in sectors) and the p value gives
the size of the partition (also in sectors). See disktab(4) for more
info. Note that DEC Unix likes to define overlapping partitions. For
the entry above, the partition layout looks like this (you can verify
this by adding up the various o and p values):

a b d e f
|---|-------|-----------|-----------|-----------|

c
|-----------------------------------------------|

g h
|-----------------|-----------------|

DEC Unix insists that partition a starts at offset 0 and that
partition c spans the entire disk. Other than that, you can setup the
partition table any way you like.

Let's suppose you have DEC Unix using partition g and want to install
Linux on partition h with partition b being a (largish) swap
partition. To get this layout without destroying the existing DEC
Unix partition, you need to set the partition types explicitly. You
can do this by adding a t field for each partition. In our case, we
add the following line to the above disktab entry.

:ta=unused:tb=swap:tg=4.2BSD:th=resrvd8:

Now why do we mark partition h as "reservd8" instead of "ext2"? Well,
DEC Unix doesn't know about Linux. It so happens that partition type
"ext2" corresponds to a numeric value of 8, and DEC Unix uses the
string "reservd8" for that value. Thus, in DEC Unix speak, "reservd8"
means "ext2". OK, this was the hard part. Now we just need to
install the updated disktab entry on the disk. Let's assume the disk
has SCSI id 5. In this case, we'd do:

# disklabel -rw /dev/rrz5c rz26

You can verify that everything is all right by reading back the
disklabel with disklabel -r /dev/rrz5c. At this point, you may want
to reboot DEC Unix and make sure the existing DEC Unix partition is
still alive and well. If that is the case, you can shut down the
machine and start with the Linux installation. Be sure to skip the
disk partitioning step during the install. Since we already installed
a good partition table, you should be able to proceed and select the
8th partition as the Linux root partition and the 2nd partition as the
swap partition. If the disk is, say, the second SCSI disk in the
machine, then the device name for these partitions would be /dev/sdb8
and /dev/sdb2, respectively (note that Linux uses letters to name the
drives and numbers to name the partitions, which is exactly reversed
from what DEC Unix does; the Linux scheme makes more sense, of course
;-).

5.2. Installing aboot

First big caveat: with the SRM firmware, you can boot one and only one
operating system per disk. For this reason, it is generally best to
have at least two SCSI disks in a machine that you want to dual-boot
between Linux and DEC Unix. Of course, you could also boot Linux from
a floppy if speed doesn't matter or over the network, if you have a
bootp-capable server. But in this section we assume you want to boot
Linux from a disk that contains one or more DEC Unix partitions.

Second big caveat: installing aboot on a disk shared with DEC Unix
renders the first and third partition unusable (since those must have
a starting offset of 0). For this reason, we recommend that you
change the size of partition a to something that is just big enough to
hold aboot (1MB should be plenty).

Once these two caveats are taken care of, installing aboot is almost
as easy as usual: since partition a and c will overlap with aboot, we
need to tell swriteboot that this is indeed OK. We can do this under
Linux with a command line of the following form (again, assuming we're
trying to install aboot on the second SCSI disk):

# swriteboot -f1 -f3 /dev/sdb bootlx

The -f1 means that we want to force writing bootlx even though it
overlaps with partition 1. The corresponding applies for partition 3.

This is it. You should now be able to shutdown the system and boot
Linux from the harddisk. In our example, the SRM command line to do
this would be:

>>> boot dka5 -fi 8/vmlinux.gz -fl root=/dev/sdb8

6. Installation of Distributions

6.1. RedHat 6.0 and 6.1

6.1.1. Installation from the Red Hat 6.0 or 6.1 CD

Red Hat have made their distribution CD bootable from SRM console (--
Please note that through the official RedHat CD-ROM is SRM bootable,
copies made by various other companies may not be bootable.--)

To start an installation, put the CD in and type the following:

>>> boot srm-device -file kernels/generic.gz -flags root=linux-device

In the above, the SRM device name and Linux device name for your CD-
ROM drive are needed. For Example if the machine had an IDE cdrom
installed as primary master the command would look like this:

>>> boot dqa0 -file kernels/generic.gz -flags "root=/dev/hda"

See the section on ``'' conventions if you don't know what these are.

6.2. SuSE 6.1

6.2.1. Installation from the SuSE 6.1 CD

The SuSE 6.1 CD is not bootable from SRM console. SuSE have an
alternative approach which involves creating two boot floppies, the
images of which are included on the CD. The boot disks can be created
in various ways, depending on the systems you have available

Writing the boot disks from a linux system The command to use is dd.
From the mount-point of SuSE CD 1, the commands are:

# dd if=disks/aboot of=/dev/fd0
# dd if=disks/install of=/dev/fd0

For writing the boot disks from a windows system, the command to use
is rawrite. It is available on the CD.

D:\tools\> rawrite

The program then prompts for input disk image and output disk drive.
Run this command once for each of the disk images as shown above.

Starting the SuSE installer from the boot disks With the floppy disk
made from the aboot image in place, type:

>>> boot dva0 -file vmlinux.gz -flags "root=/dev/fd0 load_ramdisk=1"

This will start the kernel, prompt you for the second boot disk, and
start the installer

6.3. SuSE 6.3

6.3.1. Installation from the SuSE 6.3 CD

The SuSE 6.3 CD-ROM is SRM bootable much like the RedHat 6.0 and 6.1
CD-ROMs. The best way to start the install from SRM is to use the
following command:

>>> boot srm-device -flags 0

In the above, the SRM device names for your CD-ROM drive is needed.
For Example if the machine had an IDE cdrom installed as primary
master the command would look like this:

>>> boot dqa0 -flags 0

SuSE has added support to aboot to allow it to load initrd files. The
above command will from the CD-ROM drive and use config number 0 from
the /etc/aboot.conf file. For other variations on this refer to the
SuSE installation guide.

7. Document History

v0.6.1 21 March 2000 Changes from Rich Payne <[email protected]>

o Made the installation hints a new chapter

o Added information on Netbooting

o Added to the new section on RedHat 6.1 and BSD disklabels

o Removed David Mosberger-Tang's name from the authors list

o Marked a few of the feature as being in 0.6 only

o Added info for SuSE 6.3 and RedHat 6.1

v0.6 3 March 2000 Changes and information from David Huggins-Daines
<[email protected]>

o Moved the notes on MILO vs. SRM to an "About this document" section

o Added sections on switching to SRM, and basic SRM usage

o Added section on the new interactive use of aboot

o Updated the note on DOS partition tables to mention the Red Hat 6.1
installer's behavior.

o Normalized the markup, and codified the conventions used for user-
entered commands.

o Corrected the notes on BSD disklabels (SRM does not read BSD
disklabels, it's just that they don't conflict with the boot
block).

v0.5.2 5 December 1999 Added comments and information from Stig Telfer
(stig @ alpha-processor.com).

o Added chart on SRM to Linux name mappings

o Added RedHat 6.0 and SuSE 6.1 installation information

o Added Disk Partitioning Information

v0.5.1 (Not Released) 13 November 1999 Took the original 0.5 document
and updated several parts:

o Update information on SRM booting from IDE devices

o Fixed URL to aboot source

o Update toc page to reflect MILO's future

o Included information on bootdef_dev and boot_dev to chapter 3

o Added this section

v0.5 17 August 1996 - Original Document by David Mosberger-Tang