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Jun 8, 2023
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README: use internal references in description, dedup notes on embedding initramfs #2689

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README: use internal references in description, deduplications
orangecms May 30, 2023
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31 changes: 14 additions & 17 deletions README.md
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Expand Up @@ -18,16 +18,14 @@ u-root embodies four different projects.
[cmds/core](cmds/core) for most of these.

* A way to compile many Go programs into a single binary with
[busybox mode](https://github.com/u-root/gobusybox/#readme).
[busybox mode](#build-modes).

* A way to create initramfs (an archive of files) to use with Linux kernels.
* A way to create initramfs (an archive of files) to use with Linux kernels,
[embeddable into firmware](#build-an-embeddable-u-root).

* Go bootloaders that use `kexec` to boot Linux or multiboot kernels such as
ESXi, Xen, or tboot. They are meant to be used with
[LinuxBoot](https://www.linuxboot.org). With that, parsers for
[GRUB config files](pkg/boot/grub) or
[syslinux config files](pkg/boot/syslinux) are to make transition to
LinuxBoot easier.
* Go [bootloaders](#systemboot) that use `kexec` to boot Linux or multiboot
kernels such as ESXi, Xen, or tboot. They are meant to be used with
[LinuxBoot](https://www.linuxboot.org).

# Usage

Expand Down Expand Up @@ -59,7 +57,7 @@ templates as defined in [templates.go](templates.go).

## Examples

You can now use the u-root command to build an initramfs. Here are some examples
Here are some examples of using the `u-root` command to build an initramfs,
with `$UROOT_PATH` being the path to where the u-root sources are on the disk
(explicitly specifiying this is only necessary if not running u-root inside the
root of the repository):
Expand Down Expand Up @@ -94,10 +92,6 @@ u-root ./cmds/core/{init,ls,elvish} ./cpu/cmds/cpud
The default set of packages included is all packages in
`github.com/u-root/u-root/cmds/core/...`.

You can build the initramfs built by u-root into the kernel via the
`CONFIG_INITRAMFS_SOURCE` config variable or you can load it separately via an
option in for example Grub or the QEMU command line or coreboot config variable.

`GBB_PATH` is a place that u-root will look for commands. Each colon-separated
`GBB_PATH` element is concatenated with patterns from the command-line and
checked for existence. For example:
Expand Down Expand Up @@ -396,6 +390,8 @@ u-root \
SystemBoot is a set of bootloaders written in Go. It is meant to be a
distribution for LinuxBoot to create a system firmware + bootloader. All of
these use `kexec` to boot. The commands are in [cmds/boot](cmds/boot).
Parsers are available for [GRUB](pkg/boot/grub), [syslinux](pkg/boot/syslinux),
and other config files to make the transition to LinuxBoot easier.

* `pxeboot`: a network boot client that uses DHCP and HTTP or TFTP to get a
boot configuration which can be parsed as PXELinux or iPXE configuration
Expand Down Expand Up @@ -470,12 +466,13 @@ You can do this to get a local server using the u-root srvfiles command:

Of course you have to fetch all those packages first somehow :-)

## Build an Embeddable U-root
## Build an Embeddable u-root

You can build this environment into a kernel as an initramfs, and further embed
that into firmware as a coreboot payload.
You can build the cpio image created by u-root into a Linux kernel via the
`CONFIG_INITRAMFS_SOURCE` config variable or coreboot config variable, and
further embed the kernel image into firmware as a coreboot payload.

In the kernel and coreboot case, you need to configure ethernet. We have a
In the kernel and coreboot case, you may need to configure ethernet. We have a
`dhclient` command that works for both ipv4 and ipv6. Since v6 does not yet work
that well for most people, a typical invocation looks like this:

Expand Down