Add support for rootless prepare.

Support using 'debootstrap --foreign' instead of qemu-debootstrap and
eliminate all use of sudo. Use fakeroot to preserve permissions in the
output filesystem. The finalization of the debootstrap is done on the
device side.

This change enables the use of distributions which are not compatible
with the distribution debootstrap is being run on (normally not a
supported configuration by debootstrap without --foreign), including
alternative architecture and, more importantly, different glibc
versions.

Signed-off-by: Alistair Strachan <astrachan@google.com>

Author: Alistair Strachan

README.md

@@ -40,8 +40,8 @@ section.
 
 Host:
 A machine running recent Ubuntu or Debian, with 4GB of memory and 4GB free space.
-Host needs the debootstrap and qemu-user-static packages. To install
-these, run `sudo apt-get install debootstrap qemu-user-static`.
+Host needs the debootstrap, fakeroot and qemu-user-static packages. To install
+these, run `sudo apt-get install debootstrap fakeroot qemu-user-static`.
 Other distributions may work but they are not tested.
 
 Quick Start Instructions
@@ -157,5 +157,9 @@ example for x86_64 architecture, run:
 ```
 adeb prepare --build --arch amd64 --bcc --kernelsrc /path/to/kernel-source/
 ```
+Normally you want to use --foreign too, especially if your distro's glibc
+version does not match the --distro option. This mode eliminates the need
+for root (chroot) or qemu-debootstrap, but it does cause more setup to be
+done on the device side the first time you enter adeb.
 Note: The --download option ignores the --arch flag. This is because we only
 provide pre-built filesystems for ARM64 at the moment.

androdeb

@@ -17,6 +17,7 @@ FULL=0				# Default to a minimal install
 DOWNLOAD=1			# Default to downloading from web
 SKIP_DEVICE=0			# Skip device preparation
 INSTALL_BCC=0			# Decide if BCC is to be installed
+FOREIGN=0			# Use debootstrap --foreign mode
 
 # Default packages
 PACKAGES=""
@@ -52,6 +53,7 @@ case $key in
     --full) FULL=1; config_full_build; shift || true; ;;
     --arch) ARCH=$2; shift || true; shift || true; ;;
     --distro) DISTRO="$2"; shift || true; shift || true; ;;
+    --foreign) FOREIGN=1; shift || true; ;;
     --archive) TARF=$2; shift || true; shift || true; ;;
     --bcc) source $spath/packages/bcc; shift || true;     ;;
     --kernelsrc) KERNELSRC="$2"; shift || true;     shift || true;     ;;
@@ -301,7 +303,7 @@ c_info "Using temporary directory: $TDIR"
 ex_files=$(mktemp); echo $EXTRA_FILES > $ex_files
 
 $spath/buildstrap $ARCH $DISTRO $TDIR $OUT_TMP "$PACKAGES" \
-		$ex_files $INSTALL_BCC $SKIP_DEVICE $MIRROR
+		$ex_files $INSTALL_BCC $SKIP_DEVICE $MIRROR $FOREIGN
 rm $ex_files
 
 # If we only wanted to prepare a rootfs and don't have

buildstrap

@@ -13,14 +13,20 @@ EXTRA_FILES="$(cat $6)"
 INSTALL_BCC=$7
 SKIP_DEVICE=$8		# Skip any device-specific stages
 MIRROR=$9
+shift
+FOREIGN=$9
 VARIANT="--variant=minbase"
 
-root=sudo
-
-if [ $EUID -ne 0 ]; then echo "The next stage runs as sudo, please enter password if asked."; fi
+if [ $FOREIGN -eq 1 ]; then
+	debootstrap="debootstrap --foreign"
+	root=fakeroot
+else
+	if [ $EUID -ne 0 ]; then echo "The next stage runs as sudo, please enter password if asked."; fi
+	debootstrap=qemu-debootstrap
+	root=sudo
+fi
 
-# It's easier to just really be root for debootstrap
-time $root qemu-debootstrap --arch $ARCH --include=$PACKAGES $VARIANT \
+time $root $debootstrap --arch $ARCH --include=$PACKAGES $VARIANT \
 	$DISTRO $OUT_TMP $MIRROR
 
 # Some reason debootstrap leaves these mounted
@@ -63,7 +69,7 @@ else
 fi
 
 # Add a default DNS server
-$root tee -a $OUT_TMP/etc/resolv.conf >/dev/null <<EOF
+$root tee $OUT_TMP/etc/resolv.conf >/dev/null <<EOF
 nameserver 4.2.2.2
 EOF