contrib: add rc.d script to install new kernels in build containers

contrib/zbm-builder-kernel.sh

@@ -0,0 +1,80 @@
+#!/bin/sh
+
+set -e
+
+## ZBM Builder Kernel Installer
+#
+# This rc.d script for ZFSBootMenu build containers will install a Void kernel
+# and headers specified in the environment variable ZFSBOOTMENU_KERNEL_SERIES.
+# The value of the variable should take the form `linuxY.Z` for major version Y
+# and minor version Z; the most up-to-date version released for Void in that
+# series will be installed. In addition, this script will install the Void dkms
+# package and its dependencies to allow the ZFS kernel module to be built for
+# the kernel.
+#
+# If the environment variable ZFSBOOTMENU_KERNEL_SERIES is not defined, the
+# version currently recommended by Void Linux (as indicated by the version of
+# the `linux` meta-package) will be selected.
+#
+## USAGE
+#
+# The ZFSBootMenu build container entrypoint will invoke all executables found
+# in the `rc.pre.d` and `rc.d` subdirectories of its build root. Simply install
+# this script to one of these paths (the distinction is not relevant for this
+# operation) and run the builder.
+#
+# The environment variable can be specified using the `--env` argument to
+# `podman run` or `docker run`. When using the `zbm-builder.sh` convenience
+# wrapper, its `-O` flag can be used to pass `--env` to the container runtime.
+# For example,
+#
+#     zbm-builder.sh -O --env=ZFSBOOTMENU_KERNEL_SERIES=linux6.10
+#
+# When the container is run by the `zbm-builder.sh` convenience wrapper, the
+# build directory is the path provided to the `-b` argument of the wrapper (and
+# is, by default, the current working directory). When the container is invoked
+# manually, the build directory is the path specified by the `-b` argument of
+# the entrypoint (and is, by default, the path `/build`).
+#
+# In the default configuration, ZFSBootMenu will be built with the latest
+# installed kernel. If this script is used to select a kernel series older than
+# one preinstalled in the build image, a custom config.yaml may be required in
+# the build root to create a ZFSBootMenu image using the newly installed
+# kernel.
+#
+## NOTE
+#
+# This script will not attempt to update packages. In particular, if a newer
+# version of the `zfs` package is desired, the container should be run with the
+# flags `-u -u` (yes, twice) to update packages. Alternatively, uncomment the
+# command
+#
+#     xbps-install -uy zfs
+#
+# near the end of this script.
+
+# Make sure XBPS and the repositories are up to date
+xbps-install -Suy xbps
+
+if [ -z "${ZFSBOOTMENU_KERNEL_SERIES}" ]; then
+	# Use the linux meta-package to identify a default series
+	ZFSBOOTMENU_KERNEL_SERIES="$(
+		xbps-query -Rp pkgver linux | xargs xbps-uhelper getpkgversion
+	)" || ZFSBOOTMENU_KERNEL_SERIES=""
+
+	if [ -z "${ZFSBOOTMENU_KERNEL_SERIES}" ]; then
+		echo "ERROR: unable to determine ZFSBOOTMENU_KERNEL_SERIES" >&2
+		exit 1
+	fi
+
+	ZFSBOOTMENU_KERNEL_SERIES="linux${ZFSBOOTMENU_KERNEL_SERIES%_*}"
+fi
+
+xbps-install -uy dkms \
+	"${ZFSBOOTMENU_KERNEL_SERIES}" "${ZFSBOOTMENU_KERNEL_SERIES}-headers"
+
+# To update zfs, uncomment this line
+#xbps-install -uy zfs
+
+# Make sure that the kernel module is built
+xbps-reconfigure -f zfs