Support chroot'ing into a snapshot

Author: zdykstra

90zfsbootmenu/zfs-chroot.sh

@@ -17,19 +17,17 @@ if mountpoint="$( allow_rw=yes mount_zfs "${selected}" )"; then
   mount -t proc proc "${mountpoint}/proc"
   mount -t sysfs sys "${mountpoint}/sys"
   mount -B /dev "${mountpoint}/dev"
-  mount -B /tmp "${mountpoint}/var/tmp"
+  mount -B /tmp "${mountpoint}/tmp"
   mount -t devpts pts "${mountpoint}/dev/pts"
 
-  tput clear
-  tput cnorm
-
   pool="${selected%%/*}"
 
   if is_writable "${pool}"; then
-    echo "${selected} is mounted read/write"
+    echo -n "${selected} is mounted read/write"
   else
-    echo "${selected} is mounted read-only"
+    echo -n "${selected} is mounted read-only"
   fi
+  echo -e ", /tmp is shared and read/write\n"
 
   if [ -f "${mountpoint}/bin/bash" ]; then
     _SHELL="/bin/bash"

90zfsbootmenu/zfsbootmenu-lib.sh

@@ -51,7 +51,7 @@ zerror() {
 # If the filesystem is locked, this method fails without attempting unlock
 
 mount_zfs() {
-  local fs rwo mnt ret pool
+  local fs rwo mnt ret pool is_snapshot
 
   fs="${1}"
   if be_is_locked "${fs}" >/dev/null; then
@@ -62,25 +62,35 @@ mount_zfs() {
   mnt="${BASE}/${fs}/mnt"
   test -d "${mnt}" || mkdir -p "${mnt}"
 
+  # @ always denotes a snapshot
+  if [[ "${fs}" =~ @ ]]; then
+    is_snapshot=1
+  fi
+
   # filesystems are readonly by default, but read-write mounts may be requested
   rwo="ro"
   # shellcheck disable=SC2154
   if [ -n "${allow_rw}" ]; then
     pool="${fs%%/*}"
-    if is_writable "${pool}"; then
+    if is_writable "${pool}" && [ -z "${is_snapshot}" ]; then
       rwo="rw"
     else
-      zwarn "read-write mount of ${fs} forbidden, pool ${pool} is not writable"
+      if [ -n "${is_snapshot}" ]; then
+        zwarn "read-write mount of ${fs} forbidden, filesystem is a snapshot"
+      else
+        zwarn "read-write mount of ${fs} forbidden, pool ${pool} is not writable"
+      fi
     fi
   fi
 
-  # zfsutil is required for non-legacy mounts and omitted for legacy mounts
-  if [ "x$(zfs get -H -o value mountpoint "${fs}")" = "xlegacy" ]; then
+  # zfsutil is required for non-legacy mounts and omitted for legacy mounts or snapshots
+  if [ "x$(zfs get -H -o value mountpoint "${fs}")" = "xlegacy" ] || [ -n "${is_snapshot}" ]; then
     zdebug "mounting ${fs} at ${mnt} (${rwo})"
     mount -o "${rwo}" -t zfs "${fs}" "${mnt}"
     ret=$?
   else
     zdebug "mounting ${fs} at ${mnt} (${rwo}) with zfsutil"
+    zdebug "mount -o zfsutil,${rwo} -t zfs ${fs} ${mnt}"
     mount -o "zfsutil,${rwo}" -t zfs "${fs}" "${mnt}"
     ret=$?
   fi
@@ -239,11 +249,12 @@ draw_snapshots() {
 
   header="$( header_wrap \
     "[ENTER] duplicate" "[ESC] back" "" \
-    "[ALT+D] show diff" "[ALT+X] clone and promote" "[ALT+C] clone only" "[ALT+H] help" )"
+    "[ALT+D] show diff" "[ALT+E] chroot" "" \
+    "[ALT+X] clone and promote" "[ALT+C] clone only" "[ALT+H] help" )"
 
   if ! selected="$( zfs list -t snapshot -H -o name "${benv}" |
       HELP_SECTION=SNAPSHOT ${FUZZYSEL} --prompt "Snapshot > " \
-        --tac --expect=alt-x,alt-c,alt-d \
+        --tac --expect=alt-x,alt-c,alt-d,alt-e \
         --preview="/libexec/zfsbootmenu-preview ${BASE} ${benv} ${BOOTFS}" \
         --preview-window="up:${PREVIEW_HEIGHT}" \
         --header="${header}" )"; then
@@ -1433,6 +1444,22 @@ populate_be_list() {
   return $ret
 }
 
+# arg1: ZFS filesystem
+# prints: nothing
+# returns: nothing
+
+zfs_chroot() {
+  local fs
+  fs="${1}"
+  [ -n "${fs}" ] || return
+
+  tput clear
+  tput cnorm
+
+  zdebug "chroot environment: ${fs}"
+  /bin/bash -c "zfs-chroot ${fs}"
+}
+
 
 # arg1: message
 # prints: nothing

90zfsbootmenu/zfsbootmenu.sh

@@ -186,6 +186,11 @@ while true; do
           # Return to snapshot submenu, don't redraw main menu
           BE_SELECTED=1
           continue
+        ;;
+          "alt-e")
+          zfs_chroot "${selected_snap}"
+          BE_SELECTED=1
+          continue
         ;;
         # Check available space early in the process
         "enter")
@@ -281,11 +286,7 @@ while true; do
       fi
       ;;
     "alt-c")
-      tput clear
-      tput cnorm
-      zdebug "chroot environment: ${selected_be}"
-      echo "Entering chroot for ${selected_be}"
-      /bin/bash -c "zfs-chroot ${selected_be}"
+      zfs_chroot "${selected_be}"
     ;;
   esac
 done