+ wget --progress=dot:giga -P "${image_dir}" -N "${base_image}"
+}
+
+function __kernel_modules {
+ # Load mandatory kernel modules: loop, nbd
+ local image_dir=$1
+ test -e /dev/loop-control || sudo modprobe loop
+ if sudo modprobe nbd max_part=8 || sudo modprobe -f nbd max_part=8; then
+ return 0
+ fi
+ if [ -e /dev/nbd0 ]; then return 0; fi # nbd might be inbuilt
+ # CentOS (or RHEL family in general) do not provide 'nbd' out of the box
+ echo "[WARN] 'nbd' kernel module cannot be loaded!"
+ if [ ! -e /etc/redhat-release ]; then
+ echo "[ERROR] Non-RHEL system detected, aborting!"
+ echo "[ERROR] Try building 'nbd' manually or install it from a 3rd party."
+ exit 1
+ fi
+
+ # Best-effort attempt at building a non-maintaned kernel module
+ local __baseurl
+ local __subdir
+ local __uname_r=$(uname -r)
+ local __uname_m=$(uname -m)
+ if [ "${__uname_m}" = 'x86_64' ]; then
+ __baseurl='http://vault.centos.org/centos'
+ __subdir='Source/SPackages'
+ __srpm="kernel-${__uname_r%.${__uname_m}}.src.rpm"
+ else
+ __baseurl='http://vault.centos.org/altarch'
+ __subdir="Source/${__uname_m}/Source/SPackages"
+ # NOTE: fmt varies across releases (e.g. kernel-alt-4.11.0-44.el7a.src.rpm)
+ __srpm="kernel-alt-${__uname_r%.${__uname_m}}.src.rpm"
+ fi
+
+ local __found='n'
+ local __versions=$(curl -s "${__baseurl}/" | grep -Po 'href="\K7\.[\d\.]+')
+ for ver in ${__versions}; do
+ for comp in os updates; do
+ local url="${__baseurl}/${ver}/${comp}/${__subdir}/${__srpm}"
+ if wget "${url}" -O "${image_dir}/${__srpm}" > /dev/null 2>&1; then
+ __found='y'; break 2
+ fi
+ done
+ done
+
+ if [ "${__found}" = 'n' ]; then
+ echo "[ERROR] Can't find the linux kernel SRPM for: ${__uname_r}"
+ echo "[ERROR] 'nbd' module cannot be built, aborting!"
+ echo "[ERROR] Try 'yum upgrade' or building 'nbd' krn module manually ..."
+ exit 1
+ fi
+
+ rpm -ivh "${image_dir}/${__srpm}" 2> /dev/null
+ mkdir -p ~/rpmbuild/{BUILD,BUILDROOT,RPMS,SOURCES,SPECS,SRPMS}
+ # shellcheck disable=SC2016
+ echo '%_topdir %(echo $HOME)/rpmbuild' > ~/.rpmmacros
+ (
+ cd ~/rpmbuild/SPECS
+ rpmbuild -bp --nodeps --target="${__uname_m}" kernel*.spec
+ cd ~/rpmbuild/BUILD/"${__srpm%.src.rpm}"/linux-*
+ sed -i 's/^.*\(CONFIG_BLK_DEV_NBD\).*$/\1=m/g' .config
+ # http://centosfaq.org/centos/nbd-does-not-compile-for-3100-514262el7x86_64
+ if grep -Rq 'REQ_TYPE_DRV_PRIV' drivers/block; then
+ sed -i 's/REQ_TYPE_SPECIAL/REQ_TYPE_DRV_PRIV/g' drivers/block/nbd.c
+ fi
+ gunzip -c "/boot/symvers-${__uname_r}.gz" > Module.symvers
+ make prepare modules_prepare
+ make M=drivers/block -j
+ modinfo drivers/block/nbd.ko
+ sudo mkdir -p "/lib/modules/${__uname_r}/extra/"
+ sudo cp drivers/block/nbd.ko "/lib/modules/${__uname_r}/extra/"
+ )
+ sudo depmod -a
+ sudo modprobe nbd max_part=8 || sudo modprobe -f nbd max_part=8