aboot

aboot is the Linux/Alpha bootloader for SRM. It loads a Linux kernel from an ext2, ext3, ext4, XFS (v4 and v5), ISO 9660, or UFS filesystem (or a raw disk partition) and boots it, with support for an /etc/aboot.conf configuration file, kernel argument mapping, and initial ramdisks.

Originally written by David Mosberger and extended by Michael Schwingen and Will Woods; later maintained by Debian and now upstream at https://github.com/alphalinux-org/aboot.

For background on SRM and how it loads a bootloader, see the SRM Firmware HOWTO in doc/faq/srm.html.

Building

• Edit Makefile and include/config.h to suit your needs; the defaults work for most systems. CONFIG_FILE_PARTITION in include/config.h selects the default partition for /etc/aboot.conf, but this can also be overridden on the boot command line.
• Run make. This produces the aboot image, bootlx.

Installing

Write the aboot image to a disk with swriteboot (built from the sdisklabel directory):

# swriteboot -c<boot partition #> <boot device> bootlx

For example, if the kernel images and aboot.conf live on /dev/sda2:

# swriteboot -c2 /dev/sda bootlx

Don't run this unless you're sure of the partition layout. If your system already boots, there's no need to install a new bootloader.

For ISO images, use isomarkboot (in tools/) to mark an image as bootable; netabootwrap (also in tools/) creates images for network booting.

Set the /etc/aboot.conf partition with abootconf:

# abootconf /dev/sda 2

/etc/aboot.conf needs one line per configuration, e.g.:

0:2/boot/vmlinux.gz root=/dev/sda3

or, when booting an initramfs:

0:2/boot/vmlinux.gz initrd=/boot/initramfs root=/dev/sda3

To have SRM boot Linux automatically, set these SRM environment variables (from Linux, via /proc/srm_environment/named_variables, or from the SRM console itself):

# cd /proc/srm_environment/named_variables
# echo -n 0 > boot_osflags
# echo -n '' > boot_file
# echo -n 'BOOT' > auto_action
# echo -n 'dkc100' > bootdef_dev

substituting the actual boot device for dkc100. Hit Ctrl+C during boot to get back to the SRM console if needed.

Tools

• sdisklabel/swriteboot — write aboot to a disk, set the boot partition
• tools/e2writeboot — write aboot to an ext2 filesystem
• tools/abootconf — query or set the aboot.conf partition number
• tools/isomarkboot — mark an ISO 9660 image bootable
• tools/netabootwrap — build images for network booting

Documentation

Man pages are in doc/man; the SRM Firmware HOWTO is in doc/faq.

Known issues

• EOF detection on UFS filesystems may not work correctly: reading the configuration file can hang if the desired config line isn't found.
• Netboot support and UFS support are not well exercised and may be broken.

License

See COPYING.