Add pxeboot write extension.baserock/richardmaw/pxeboot-write

It has 4 modes.

1.  Specify PXEBOOT_DEPLOYER_INTERFACE and PXEBOOT_VLAN to
    configure the target to pxeboot on a vlan and spawn a dhcp, nfs and
    tftp server. This is potentially the fastest, since it doesn't need
    to copy data to other servers.

2.  Specify PXEBOOT_DEPLOYER_INTERFACE without PXEBOOT_VLAN to
    configure do 1, but without creating the vlan interface. This
    assumes that you have exclusive access to the interface, such as if
    you're plugged in to the device directly, or your interface is
    vlanned by your infrastructure team.

    This is required if you are serving from a VM and bridging it to the
    correct network via macvtap. For this to work, you need to macvtap
    bridge to a pre-vlanned interface on your host machine.

3.  Specify PXEBOOT_DEPLOYER_INTERFACE and PXEBOOT_CONFIG_TFTP_ADDRESS
    to put config on an existing tftp server, already configured by the
    dhcp server.

    This spawns a tftp server and configures the local nfs server, but
    doesn't do a dhcp server. This is useful if you have already got a
    dhcp server that serves PXE images.

4.  Specify at least PXEBOOT_CONFIG_TFTP_ADDRESS and
    PXEBOOT_ROOTFS_RSYNC_ADDRESS to specify existing servers to copy
    config, kernels and the rootfs to.

The mode detection can be overridden by specifying PXEBOOT_MODE.
Mode 1 is `spawn-vlan`. Mode 2 is `spawn-novlan`, Mode 3 is
`existing-dhcp` and Mode 4 is `existing-server`.

1 files changed, 123 insertions, 0 deletions

diff --git a/pxeboot.write.help b/pxeboot.write.help
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+help: >
+    pxeboot.write extension.
+
+
+    This write extension will serve your generated system over NFS to
+    the target system.
+
+    In all modes `location` is the mac address of the interface that
+    the target will PXE boot from. This is used so that the target will
+    load the configuration file appropriate to it.
+
+
+    # `PXEBOOT_MODE`
+
+
+    It has 4 modes, which can be specified with PXEBOOT_MODE, or inferred
+    from which parameters are passed:
+
+
+    ## spawn-vlan
+
+
+    Specify PXEBOOT_DEPLOYER_INTERFACE and PXEBOOT_VLAN to configure
+    the target to pxeboot on a vlan and spawn a dhcp, nfs and tftp
+    server. This is potentially the fastest, since it doesn't need to
+    copy data to other servers.
+
+    This will create a vlan interface for the interface specified in
+    PXEBOOT_DEPLOYER_INTERFACE and spawn a dhcp server which serves
+    pxelinux.0, a configuration file and a kernel image from itself.
+
+    The configuration file informs the target to boot with a kernel
+    command-line that uses an NFS root served from the deployment host.
+
+
+    ## spawn-novlan
+
+
+    Specify PXEBOOT_DEPLOYER_INTERFACE without PXEBOOT_VLAN to configure
+    like `spawn-vlan`, but without creating the vlan interface.
+
+    This assumes that you have exclusive access to the interface, such
+    as if you're plugged in to the device directly, or your interface
+    is vlanned by your infrastructure team.
+
+    This is required if you are serving from a VM and bridging it to the
+    correct network via macvtap. For this to work, you need to macvtap
+    bridge to a pre-vlanned interface on your host machine.
+    
+
+    ## existing-dhcp
+
+
+    Specify PXEBOOT_DEPLOYER_INTERFACE and PXEBOOT_CONFIG_TFTP_ADDRESS
+    to put config on an existing tftp server, already configured by the
+    dhcp server.
+
+    This spawns a tftp server and configures the local nfs server, but
+    doesn't spawn a dhcp server. This is useful if you have already got a
+    dhcp server that serves PXE images.
+
+    PXEBOOT_CONFIG_TFTP_ADDRESS is a URL in the form `sftp://$HOST/$PATH`. 
+    The configuration file is copied to `$PATH/pxelinux.cfg/` on the
+    target identified by `$HOST`.
+
+
+    ## existing-server
+
+
+    Specify at least PXEBOOT_CONFIG_TFTP_ADDRESS and
+    PXEBOOT_ROOTFS_RSYNC_ADDRESS to specify existing servers to copy
+    config, kernels and the rootfs to.
+
+    Configuration is copied to the target as `existing-dhcp`.
+
+    Specify PXEBOOT_KERNEL_TFTP_ADDRESS if the tftp server that the
+    kernel must be downloaded from is different to that of the pxelinux
+    configuration file.
+
+    PXEBOOT_ROOTFS_RSYNC_ADDRESS is a rsync URL describing where to copy
+    nfsroots to where they will be exported by the NFS server.
+
+    Specify PXEBOOT_ROOTFS_NFSROOT if the nfsroot appears as a different
+    address from the target's perspective.
+
+
+    # IPMI commands
+
+
+    After the PXE boot has been set up, the target needs to be rebooted
+    in PXE mode.
+
+    If the target is IPMI enabled, you can set `IPMI_USER`, `IPMI_HOST`
+    and `IPMI_PASSWORD` to make it reboot the target into netboot mode
+    automatically.
+
+    If they are not specified, then instructions will be displayed, and
+    `pxeboot.write` will wait for you to finish.
+
+    If there are command-line automation tools for rebooting the target
+    in netboot mode, then appropriate commands can be defined in the
+    following variables.
+
+
+    ## PXEBOOT_PXE_REBOOT_COMMAND
+
+
+    This command will be used to reboot the target device with its boot
+    device set to PXE boot.
+
+
+    ## PXEBOOT_REBOOT_COMMAND
+
+
+    This command will be used to reboot the target device in its default
+    boot mode.
+
+
+    ## PXEBOOT_WAIT_INSTALL_COMMAND
+
+
+    If it is possible for the target to notify you that it has finished
+    installing, you can put a command in here to wait for the event.