vmtest: add debootstrap-based mkrootfs script

The existing mkrootfs.sh is based on Arch Linux, which supports only
x86_64.

Add mkrootfs_debian.sh: a debootstrap-based script. Debian was chosen,
because it supports more architectures than other mainstream distros.
Move init setup to mkrootfs_tweak.sh, rename the existing Arch script
to mkrootfs_arch.sh.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>

travis-ci/vmtest/mkrootfs_arch.sh

@@ -100,59 +100,7 @@ rm -rf "$root/var/lib/pacman/sync/"
 # We don't need any documentation.
 rm -rf "$root/usr/share/{doc,help,man,texinfo}"
 
-chroot "${root}" /bin/busybox --install
+"$(dirname "$0")"/mkrootfs_tweak.sh "$root"
 
-cat > "$root/etc/inittab" << "EOF"
-::sysinit:/etc/init.d/rcS
-::ctrlaltdel:/sbin/reboot
-::shutdown:/sbin/swapoff -a
-::shutdown:/bin/umount -a -r
-::restart:/sbin/init
-EOF
-chmod 644 "$root/etc/inittab"
-
-mkdir -m 755 "$root/etc/init.d" "$root/etc/rcS.d"
-cat > "$root/etc/rcS.d/S10-mount" << "EOF"
-#!/bin/sh
-
-set -eux
-
-/bin/mount proc /proc -t proc
-
-# Mount devtmpfs if not mounted
-if [[ -z $(/bin/mount -l -t devtmpfs) ]]; then
-	/bin/mount devtmpfs /dev -t devtmpfs
-fi
-
-/bin/mount sysfs /sys -t sysfs
-/bin/mount bpffs /sys/fs/bpf -t bpf
-/bin/mount debugfs /sys/kernel/debug -t debugfs
-
-echo 'Listing currently mounted file systems'
-/bin/mount
-EOF
-chmod 755 "$root/etc/rcS.d/S10-mount"
-
-cat > "$root/etc/rcS.d/S40-network" << "EOF"
-#!/bin/sh
-
-set -eux
-
-ip link set lo up
-EOF
-chmod 755 "$root/etc/rcS.d/S40-network"
-
-cat > "$root/etc/init.d/rcS" << "EOF"
-#!/bin/sh
-
-set -eux
-
-for path in /etc/rcS.d/S*; do
-	[ -x "$path" ] && "$path"
-done
-EOF
-chmod 755 "$root/etc/init.d/rcS"
-
-chmod 755 "$root"
 tar -C "$root" -c . | zstd -T0 -19 -o "$NAME"
 chmod 644 "$NAME"

travis-ci/vmtest/mkrootfs_debian.sh

@@ -0,0 +1,40 @@
+#!/bin/bash
+# This script builds a Debian root filesystem image for testing libbpf in a
+# virtual machine. Requires debootstrap >= 1.0.95 and zstd.
+
+set -e -u -x -o pipefail
+
+# Check whether we are root now in order to avoid confusing errors later.
+if [ "$(id -u)" != 0 ]; then
+	echo "$0 must run as root" >&2
+	exit 1
+fi
+
+# Create a working directory and schedule its deletion.
+root=$(mktemp -d -p "$PWD")
+trap 'rm -r "$root"' EXIT
+
+# Install packages.
+packages=binutils,busybox,elfutils,iproute2,libcap2,libelf1,strace,zlib1g
+debootstrap --include="$packages" --variant=minbase bullseye "$root"
+
+# Remove the init scripts (tests use their own). Also remove various
+# unnecessary files in order to save space.
+rm -rf \
+	"$root"/etc/rcS.d \
+	"$root"/usr/share/{doc,info,locale,man,zoneinfo} \
+	"$root"/var/cache/apt/archives/* \
+	"$root"/var/lib/apt/lists/*
+
+# Save some more space by removing coreutils - the tests use busybox. Before
+# doing that, delete the buggy postrm script, which uses the rm command.
+rm -f "$root/var/lib/dpkg/info/coreutils.postrm"
+chroot "$root" dpkg --remove --force-remove-essential coreutils
+
+# Apply common tweaks.
+"$(dirname "$0")"/mkrootfs_tweak.sh "$root"
+
+# Save the result.
+name="libbpf-vmtest-rootfs-$(date +%Y.%m.%d).tar.zst"
+rm -f "$name"
+tar -C "$root" -c . | zstd -T0 -19 -o "$name"

travis-ci/vmtest/mkrootfs_tweak.sh

@@ -0,0 +1,61 @@
+#!/bin/bash
+# This script prepares a mounted root filesystem for testing libbpf in a virtual
+# machine.
+set -e -u -x -o pipefail
+root=$1
+shift
+
+chroot "${root}" /bin/busybox --install
+
+cat > "$root/etc/inittab" << "EOF"
+::sysinit:/etc/init.d/rcS
+::ctrlaltdel:/sbin/reboot
+::shutdown:/sbin/swapoff -a
+::shutdown:/bin/umount -a -r
+::restart:/sbin/init
+EOF
+chmod 644 "$root/etc/inittab"
+
+mkdir -m 755 -p "$root/etc/init.d" "$root/etc/rcS.d"
+cat > "$root/etc/rcS.d/S10-mount" << "EOF"
+#!/bin/sh
+
+set -eux
+
+/bin/mount proc /proc -t proc
+
+# Mount devtmpfs if not mounted
+if [[ -z $(/bin/mount -l -t devtmpfs) ]]; then
+	/bin/mount devtmpfs /dev -t devtmpfs
+fi
+
+/bin/mount sysfs /sys -t sysfs
+/bin/mount bpffs /sys/fs/bpf -t bpf
+/bin/mount debugfs /sys/kernel/debug -t debugfs
+
+echo 'Listing currently mounted file systems'
+/bin/mount
+EOF
+chmod 755 "$root/etc/rcS.d/S10-mount"
+
+cat > "$root/etc/rcS.d/S40-network" << "EOF"
+#!/bin/sh
+
+set -eux
+
+ip link set lo up
+EOF
+chmod 755 "$root/etc/rcS.d/S40-network"
+
+cat > "$root/etc/init.d/rcS" << "EOF"
+#!/bin/sh
+
+set -eux
+
+for path in /etc/rcS.d/S*; do
+	[ -x "$path" ] && "$path"
+done
+EOF
+chmod 755 "$root/etc/init.d/rcS"
+
+chmod 755 "$root"