From 62775e2d68b310725560b85da99c85632b525874 Mon Sep 17 00:00:00 2001
From: Andrew Cady <d@jerkface.net>
Date: Sat, 21 Aug 2021 18:48:47 -0400
Subject: initial

---
 forkroot | 120 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 120 insertions(+)
 create mode 100755 forkroot

diff --git a/forkroot b/forkroot
new file mode 100755
index 0000000..1ab4244
--- /dev/null
+++ b/forkroot
@@ -0,0 +1,120 @@
+#!/bin/bash
+die() { printf 'Error: %s\n' "$*"; exit 1; }
+if [ $UID != 0 ]
+then
+    exec sudo -- "$0" "$@" || die 'You are not root.'
+fi
+
+help()
+{
+    printf '%s\n' "Usage: $0 [-h|--help] [--] <target directory>"
+}
+
+unset force delete verbose
+while [ $# -gt 0 ]
+do
+    case "$1" in
+        -h|--help) help; exit;;
+        --force) force=y ;;
+        --delete-after) delete=y ;;
+        -v) verbose=y ;;
+        --) shift; break ;;
+        -*) die unknown option ;;
+        *) break;
+    esac
+    shift
+done
+
+[ $# = 1 ] || die 'You must specify a target directory to create.'
+
+target=$1
+root=$target/root
+mkdir "$target" || die 'creating target directory'
+
+btrfs subvolume snapshot / "$root"
+
+verbosely()
+{
+    (
+        if [ "$verbose" ]
+        then set -x
+        fi
+        "$@"
+    )
+}
+
+bind_it()
+{
+    verbosely mount --bind "$mountpoint" "$root"/"$mountpoint"
+}
+
+copy_mountpoint()
+{
+    [ "$1" -a "$2" ] || return
+
+    [ -d "$2" ] && return
+    [ -d "${2%/*}" ] || copy_mountpoint "${1%/*}" "${2%/*}"
+    mkdir -p "$2"
+    chown --reference "$1" "$2"
+    chmod --reference "$1" "$2"
+}
+
+mounts=$(tempfile)
+cat /proc/mounts > "$mounts"
+
+while read mountdev mountpoint fstype fsoptions _
+do
+    case "$mountpoint" in
+        /sys  |/proc  |/dev   |/usr | /usr/local) bind_it; continue ;;
+        /sys/*|/proc/*|/dev/* ) continue ;;
+    esac
+    case "$PWD" in
+        "$mountpoint"/*) bind_it; continue ;;
+    esac
+
+    case "$fstype" in
+        tmpfs)
+            case "$mountpoint" in
+                /run/*) copy_mountpoint "$mountpoint" "$root"/"$mountpoint" ;;
+            esac
+            mount "$mountdev" -t "$fstype" -o "$fsoptions" "$root"/"$mountpoint" ;;
+    esac
+done < "$mounts"
+
+tac "$mounts" |
+while read mountdev mountpoint fstype fsoptions _
+do
+    case "$mountpoint" in "$root"/*) verbosely umount -l "$mountpoint";; esac
+done
+
+chroot "$root" /bin/bash
+
+confirm()
+{
+    cat <<EOF
+The following command will execute:
+
+
+
+    $*
+
+
+
+The data will be permanently lost.
+
+EOF
+    read -p "Continue?  [y/N]> " line
+    case "$line" in
+        [yY]) "$@"; return ;;
+    esac
+}
+
+if [ "$delete" -a "$force" ]
+then
+    btrfs subvolume delete "$target"/root
+    rmdir "$target"
+elif [ "$delete" ]
+then
+    confirm btrfs subvolume delete "$target"/root
+    rmdir "$target"
+fi
-- 
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