debootstrap.sh: debootstrap wrapper

1 files changed, 207 insertions, 0 deletions

diff --git a/debootstrap.sh b/debootstrap.sh
new file mode 100755
index 0000000..e0bbc4b
--- /dev/null
+++ b/debootstrap.sh
@@ -0,0 +1,207 @@
+#!/bin/sh
+imgdir=./debootstrap
+warn() { printf 'Warning: %s\n' "$*" >&2; }
+die() { printf 'Error: %s\n' "$*" >&2; exit 1; }
+[ -d "$imgdir" ] || die "directory does not exist: $imgdir"
+
+usage()
+{
+    cat <<EOF >&2
+Usage:
+  $0 init <suite>
+  $0 new <suite> <new-name>
+  $0 clone <suite> <source-name> <new-name>
+  $0 chroot <suite> <name>
+  $0 list
+
+EOF
+    list
+    exit 1
+}
+
+list()
+{
+    local f suite name header_printed=
+    for f in $imgdir/*.btrfs; do
+        [ -e "$f" ] || continue
+        f=${f##*/}
+        f=${f%.btrfs}
+        case "$f" in *.*) continue ;; esac
+        suite=${f%%-*}
+        [ "$header_printed" ] || echo 'Existing initialized suites:'
+        printf '  %s\n' "$suite"
+        header_printed=y
+    done
+    header_printed=
+    for f in $imgdir/*.*.btrfs; do
+        [ -e "$f" ] || continue
+        f=${f##*/}
+        f=${f%.btrfs}
+        suite=${f%%-*}
+        name=${f##*.}
+        [ "$header_printed" ] || echo 'Existing images:'
+        printf '  %s %s\n' "$suite" "$name"
+        header_printed=y
+    done
+}
+
+validate_suite()
+{
+    case "$1" in
+        jessie|stretch|sid) return 0 ;;
+        *) return 1 ;;
+    esac
+}
+
+i_am_root() { [ "$(id -u)" = 0 ]; }
+
+btrfs_show_subvolume_id()
+{
+    local result path="$1"
+    result=$(btrfs subvolume show "$path" | sed -n -e 's/^[ \t]*Subvolume ID:[ \t]*//p; s/.*is toplevel subvolume/5/p')
+    if [ "$result" ]
+    then printf '%s\n' "$result"
+    else false
+    fi
+}
+
+mkfs_btrfs()
+{
+    local target="$1"
+    mountpoint="$2" # can't be local because of trap
+
+    mkfs.btrfs "$target"                                    || die "mkfs.btrfs failed"
+    mount -t btrfs "$target" "$mountpoint"                  || die "mount failed"
+    trap 'umount "$mountpoint"' EXIT
+
+    btrfs subvolume create "$mountpoint"/root               || die "command 'btrfs subvolume create' failed"
+    mkdir -p "$mountpoint"/root/var/cache/apt
+    btrfs subvolume create "$mountpoint"/root/var/cache/apt/archives || die "command 'btrfs subvolume create' failed"
+    subvol_id=$(btrfs_show_subvolume_id "$mountpoint"/root)          || die "could not find btrfs subvolume name"
+    btrfs subvolume set-default "$subvol_id" "$mountpoint"           || die "command 'btrfs subvolume set-default' failed"
+
+    trap - EXIT
+    umount "$mountpoint"
+}
+
+suite_to_basename()
+{
+    suite=$1
+    variant=minbase
+    arch=$(dpkg-architecture -q DEB_HOST_ARCH) || die "command 'dpkg-architecture' failed"
+
+    printf '%s\n' "$suite-$variant-$arch.btrfs"
+}
+
+suite_name_to_imagename()
+{
+    suite=$1
+    name=$2
+    variant=minbase
+    arch=$(dpkg-architecture -q DEB_HOST_ARCH) || die "command 'dpkg-architecture' failed"
+
+    printf '%s/%s-%s-%s.%s.btrfs\n' "$imgdir" "$suite" "$variant" "$arch" "$name"
+}
+
+chroot_image()
+{
+    suite=$1
+    name=$2
+    [ "$suite" -a "$name" ] || usage
+    imagename=$(suite_name_to_imagename "$suite" "$name")
+    [ -e "$imagename" ] || die "no such file: $imagename"
+    [ -d "$imagename".mnt ] || mkdir "$imagename".mnt || die "mkdir"
+    mountpoint -q "$imagename".mnt || mount "$imagename" "$imagename".mnt || die "mount"
+
+    unshare -f -m -p \
+            chroot "$imagename".mnt \
+            /bin/sh -c 'mount -t proc proc /proc; mount -t devpts devpts /dev/pts; exec /bin/bash'
+
+    r=$?
+    umount "$imagename".mnt
+    rmdir "$imagename".mnt
+    return $r
+}
+
+clone()
+{
+    suite=$1
+    source_name=$2
+    name=$3
+    [ "$suite" -a "$name" -a "$source_name" ] || usage
+    image_basename=$imgdir/$(suite_to_basename "$suite") || die 'suite_to_basename'
+
+    source=${image_basename%.btrfs}.$source_name.btrfs
+    dest=${image_basename%.btrfs}.$name.btrfs
+
+    [ -e "$source" ] || die "source image not found -- run '$0 new $suite $source_name' to create it"
+    [ ! -e "$dest" ] || die "file exists: $dest"
+    cp --reflink=always "$source" "$dest"
+}
+
+new()
+{
+    suite=$1
+    name=$2
+    [ "$suite" -a "$name" ] || usage
+    image_basename=$imgdir/$(suite_to_basename "$suite") || die 'suite_to_basename'
+
+    source=$image_basename
+    dest=${source%.btrfs}.$name.btrfs
+
+    [ -e "$source" ] || die "source image not found -- run '$0 init $suite' to create it"
+    [ ! -e "$dest" ] || die "file exists: $dest"
+    cp --reflink=always "$source" "$dest"
+}
+
+init()
+{
+    suite=$1
+    variant=minbase
+    arch=$(dpkg-architecture -q DEB_HOST_ARCH) || die "command 'dpkg-architecture' failed"
+
+    size=1G # truncate(1) format
+
+    i_am_root || die 'you are not root'
+
+    validate_suite "$suite" || die "invalid suite: '$suite'"
+
+    target=$imgdir/$suite-$variant-$arch.btrfs
+    [ -e "$target" ] && return
+    [ -e "$target".tmp ] && die "refusing to overwrite existing temporary file: $target.tmp"
+
+    [ -d "$target".mnt ] || mkdir "$target".mnt || die "could not create directory $target.mnt"
+
+    truncate -s "$size" "$target".tmp          || die "truncate failed"
+    mkfs_btrfs "$target".tmp "$target".mnt     || die "btrfs filesystem creation failed"
+    mount -t btrfs "$target".tmp "$target".mnt || die "mount failed"
+    trap 'umount "$target.mnt"' EXIT
+
+    debootstrap_efficiently "$arch" "$variant" "$suite" \
+                            "$target".mnt "${target%.btrfs}".debs.txt || die "debootstrap failed"
+
+    if umount "$target".mnt
+    then trap - EXIT
+    else warn "umount failed"
+    fi
+
+    mv "$target".tmp "$target"
+}
+
+debootstrap_efficiently()
+{
+    local arch="$1" variant="$2" suite="$3" target="$4" savedebs="$5"
+    set -- --arch "$arch" --variant "$variant" "$suite" "$target"
+    debs=$(debootstrap --print-debs --keep-debootstrap-dir "$@" | tee "$savedebs") || die "debootstrap failed"
+    for deb in $debs; do
+        cp /var/cache/apt/archives/${deb}_* $target/var/cache/apt/archives/
+    done
+
+    debootstrap "$@" || die "debootstrap failed"
+}
+
+case "$1" in
+    init|new|clone|list) cmd=$1; shift; $cmd "$@" ;;
+    chroot) cmd=chroot_image; shift; $cmd "$@" ;;
+    *) usage ;;
+esac