Issue 2247: draft implementation of 'mountonly' workflow.

doc/user-guide/04-scenarios.adoc

@@ -1331,3 +1331,107 @@ Finished recovering your system. You can explore it under '/mnt/local'.
 
 Finished in 361 seconds.
 ----
+
+== Using ReaR to mount and repair your system
+Instead of using your ReaR image to completely recover your system from bare
+metal (as illustrated in most of the above scenarios), you can also use it
+as a live media to boot a broken but hopefully repairable system.
+
+Once booted on your recovery image, the `mountonly` workflow will:
+
+* activate all Volume Groups
+
+* offer to decrypt any LUKS-encrypted filesystem that may be present
+
+* mount all the target filesystems (including the most important virtual 
+  ones) below `/mnt/local`
+
+thereby making it possible for you to explore your system at will,
+correcting any configuration mistake that may have prevented its startup, 
+or allowing you to simply `chroot` into it and further repair it using its 
+own administrative tools.
+
+One important point to remember is that the `mountonly` workflow on its own 
+won't modify the target system in any way. Of course, once the target 
+filesystems are mounted you, as the administrator, may decide to do so
+manually.
+
+**Beware:** The `mountonly` workflow can only be used on the system where
+the rescue image was generated, as it bases its logic on the filesystem
+layout description file generated during the run of the `mkrescue` or
+`mkbackup` workflows.
+
+Here are the steps you would typically follow:
+
+=== Create your recovery image
+Using any of the techniques described in the other scenarios, create a 
+ReaR recovery image for your system (through `rear mkrescue` or `rear 
+mkbackup`). If you only take the `mountonly` workflow into consideration, it 
+doesn't matter whether you also make a backup of your system or not 
+(obviously, you'd better cover all your bases and make sure you'd be able to 
+perform a full `recover` as well should the need occur).
+
+Please note, that by default ReaR only includes in the recovery image the 
+tools it will need to recover the system. If you anticipate the need for 
+some extra tools in the context of a repair operation (e.g. tools that you 
+might need in the event `chroot`ing into the target system doesn't work), you 
+should make sure to include them in your recovery image by adding to the 
+`PROGS` or `REQUIRED_PROGS` configuration variables (please refer to the 
+comments in `default.conf` for the exact meaning of each).
+
+=== Booting on the recovery image
+Arrange for the target system to boot on your recovery image as you would in
+any of the other scenarios.
+
+=== Launching the "mount only" workflow
+Issue the `rear mountonly` command to launch the workflow (that one is always 
+verbose):
+
+----
+RESCUE pc-pan:~ # rear mountonly
+Relax-and-Recover 2.5 / Git
+Running rear mountonly (PID 625)
+Using log file: /var/log/rear/rear-pc-pan.log
+Running workflow mountonly within the ReaR rescue/recovery system
+Comparing disks
+Device sda has expected (same) size 34359738368 (will be used for 'mountonly')
+Disk configuration looks identical
+Proceed with 'mountonly' (yes) otherwise manual disk layout configuration is enforced
+(default 'yes' timeout 30 seconds)
+yes
+User confirmed to proceed with 'mountonly'
+Start target system mount.
+Mounting filesystem /
+Mounting filesystem /home
+Mounting filesystem /boot/efi
+Please enter the password for LUKS device cr_vg00-lvol4 (/dev/mapper/vg00-lvol4):
+Enter passphrase for /dev/mapper/vg00-lvol4: 
+Mounting filesystem /products
+Disk layout processed.
+Finished 'mountonly'. The target system is mounted at '/mnt/local'.
+Exiting rear mountonly (PID 625) and its descendant processes ...
+Running exit tasks
+----
+
+As you can see in the output above, you will first be asked to confirm 
+running the workflow (`Proceed with 'mountonly'`) -- simply press return. 
+All the target filesystems should now be mounted below `/mnt/local` (including 
+LUKS-encrypted ones if present and all needed virtual ones). In case any of 
+them fails to mount, you will be offered to review the mount script and to 
+re-execute it if needed.
+
+Once the system is in the desired state, you can start exploring it, correcting
+any configuration mistake or filesystem corruption that prevented it from 
+booting properly. In this state, the only tools at your disposal are those 
+included by default in ReaR recovery image, or those you saw fit to add
+yourself (see above).
+
+If this is not enough and you need to run the native administrative tools
+hosted inside your target system (such as YaST in the case of SUSE 
+distributions), you are now in a position where you can `chroot` inside 
+your system to reach them (`chroot /mnt/local`).
+
+=== Closing the session
+Once done, don't forget to leave the `chroot` environment if applicable 
+(Ctrl-D), then issue the `shutdown` command. This will ensure that all the 
+target filesystems will be cleanly unmounted before the system is restarted.

usr/sbin/rear

@@ -236,7 +236,7 @@ ARGS=( "$@" )
 
 # The following workflows are always verbose:
 case "$WORKFLOW" in
-    (validate|shell|recover)
+    (validate|shell|recover|mountonly)
         VERBOSE=1
         ;;
 esac

usr/share/rear/check/GNU

@@ -0,0 +1 @@
+../verify/GNU

usr/share/rear/check/default

@@ -0,0 +1 @@
+../verify/default

usr/share/rear/final-mount/default/110_bind_mount_proc_sys_dev_run.sh

@@ -0,0 +1 @@
+../../finalize/default/110_bind_mount_proc_sys_dev_run.sh

usr/share/rear/final-mount/default/900_remount_sync.sh

@@ -0,0 +1 @@
+../../finalize/default/900_remount_sync.sh

usr/share/rear/finalize/default/900_remount_sync.sh

@@ -14,8 +14,8 @@
 # scripts that do umount plus sync to safely shut down the recovery system,
 # cf. https://github.com/rear/rear/pull/1011
 
-# Skip if not recover WORKFLOW:
-test "recover" = "$WORKFLOW" || return 0
+# Skip if not 'recover' or 'mountonly' WORKFLOW:
+test "recover" = "$WORKFLOW" -o "mountonly" = "$WORKFLOW" || return 0
 
 # Skip if systemd is used
 # systemctl gets copied into the recovery system as /bin/systemctl:

usr/share/rear/init/default/050_check_rear_recover_mode.sh

@@ -1,5 +1,6 @@
 # In the ReaR rescue/recovery system the only possible workflows are
 # - 'recover' and its partial workflows 'layoutonly' 'restoreonly' 'finalizeonly'
+# - 'mountonly'
 # - 'opaladmin'
 # - 'help'
 # cf. https://github.com/rear/rear/issues/987
@@ -8,7 +9,7 @@
 # In the ReaR rescue/recovery system /etc/rear-release is unique (it does not exist otherwise):
 test -f /etc/rear-release || return 0
 case "$WORKFLOW" in
-    (recover|layoutonly|restoreonly|finalizeonly|opaladmin|help)
+    (recover|layoutonly|restoreonly|finalizeonly|mountonly|opaladmin|help)
         LogPrint "Running workflow $WORKFLOW within the ReaR rescue/recovery system"
         ;;
     (*)

usr/share/rear/layout/do-mount/default/100_confirm_layout_code.sh

@@ -0,0 +1 @@
+../../recreate/default/100_confirm_layout_code.sh

usr/share/rear/layout/do-mount/default/200_run_layout_code.sh

@@ -0,0 +1 @@
+../../recreate/default/200_run_layout_code.sh

usr/share/rear/layout/do-mount/default/250_verify_mount.sh

@@ -0,0 +1 @@
+../../recreate/default/250_verify_mount.sh

usr/share/rear/layout/prep-for-mount/GNU/Linux/100_include_partition_code.sh

@@ -0,0 +1 @@
+../../../prepare/GNU/Linux/100_include_partition_code.sh

usr/share/rear/layout/prep-for-mount/GNU/Linux/110_include_lvm_code.sh

@@ -0,0 +1 @@
+../../../prepare/GNU/Linux/110_include_lvm_code.sh

usr/share/rear/layout/prep-for-mount/GNU/Linux/120_include_raid_code.sh

@@ -0,0 +1 @@
+../../../prepare/GNU/Linux/120_include_raid_code.sh

usr/share/rear/layout/prep-for-mount/GNU/Linux/131_include_filesystem_code.sh

@@ -0,0 +1 @@
+../../../prepare/GNU/Linux/131_include_filesystem_code.sh

usr/share/rear/layout/prep-for-mount/GNU/Linux/133_include_mount_filesystem_code.sh

@@ -0,0 +1 @@
+../../../prepare/GNU/Linux/133_include_mount_filesystem_code.sh

usr/share/rear/layout/prep-for-mount/GNU/Linux/135_include_btrfs_subvolumes_generic_code.sh

@@ -0,0 +1 @@
+../../../prepare/GNU/Linux/135_include_btrfs_subvolumes_generic_code.sh

usr/share/rear/layout/prep-for-mount/GNU/Linux/136_include_btrfs_subvolumes_SLES_code.sh

@@ -0,0 +1 @@
+../../../prepare/GNU/Linux/136_include_btrfs_subvolumes_SLES_code.sh

usr/share/rear/layout/prep-for-mount/GNU/Linux/140_include_swap_code.sh

@@ -0,0 +1 @@
+../../../prepare/GNU/Linux/140_include_swap_code.sh

usr/share/rear/layout/prep-for-mount/GNU/Linux/150_include_drbd_code.sh

@@ -0,0 +1 @@
+../../../prepare/GNU/Linux/150_include_drbd_code.sh

usr/share/rear/layout/prep-for-mount/GNU/Linux/160_include_luks_code.sh

@@ -0,0 +1 @@
+../../../prepare/GNU/Linux/160_include_luks_code.sh

usr/share/rear/layout/prep-for-mount/GNU/Linux/170_include_hpraid_code.sh

@@ -0,0 +1 @@
+../../../prepare/GNU/Linux/170_include_hpraid_code.sh

usr/share/rear/layout/prep-for-mount/GNU/Linux/180_include_opaldisk_code.sh

@@ -0,0 +1 @@
+../../../prepare/GNU/Linux/180_include_opaldisk_code.sh

usr/share/rear/layout/prep-for-mount/GNU/Linux/210_load_multipath.sh

@@ -0,0 +1 @@
+../../../prepare/GNU/Linux/210_load_multipath.sh

usr/share/rear/layout/prep-for-mount/default/010_prepare_files.sh

@@ -0,0 +1 @@
+../../prepare/default/010_prepare_files.sh

usr/share/rear/layout/prep-for-mount/default/250_compare_disks.sh

@@ -0,0 +1 @@
+../../prepare/default/250_compare_disks.sh

usr/share/rear/layout/prep-for-mount/default/270_overrule_migration_mode.sh

@@ -0,0 +1 @@
+../../prepare/default/270_overrule_migration_mode.sh

usr/share/rear/layout/prep-for-mount/default/300_map_disks.sh

@@ -0,0 +1 @@
+../../prepare/default/300_map_disks.sh

usr/share/rear/layout/prep-for-mount/default/310_remove_exclusions.sh

@@ -0,0 +1 @@
+../../prepare/default/310_remove_exclusions.sh

usr/share/rear/layout/prep-for-mount/default/320_apply_mappings.sh

@@ -0,0 +1 @@
+../../prepare/default/320_apply_mappings.sh

usr/share/rear/layout/prep-for-mount/default/500_confirm_layout_file.sh

@@ -0,0 +1 @@
+../../prepare/default/500_confirm_layout_file.sh

usr/share/rear/layout/prep-for-mount/default/510_list_dependencies.sh

@@ -0,0 +1 @@
+../../prepare/default/510_list_dependencies.sh

usr/share/rear/layout/prep-for-mount/default/520_exclude_components.sh

@@ -0,0 +1 @@
+../../prepare/default/520_exclude_components.sh

usr/share/rear/layout/prep-for-mount/default/540_generate_device_code.sh

@@ -0,0 +1,69 @@
+# Use the dependencies to order device processing and generate code for them.
+
+# LAYOUT_CODE is the script to mount the target system based on its disk 
+# layout (diskrestore.sh).
+
+save_original_file "$LAYOUT_CODE"
+
+# Initialize diskrestore.sh:
+cat <<EOF >"$LAYOUT_CODE"
+#!/bin/bash
+
+# Create "breadcrumb" file (used as interlock by other workflows),
+# defined and checked by ./setup/default/002_clean_start.sh
+echo "$WORKFLOW" > $BREADCRUMB
+
+LogPrint "Start target system mount."
+
+mkdir -p $TARGET_FS_ROOT
+if create_component "vgchange" "rear" ; then
+    lvm vgchange -a y >/dev/null
+    component_created "vgchange" "rear"
+fi
+
+set -e
+set -x
+
+EOF
+
+# Populate diskrestore.sh with further code to (re)-mount all disk layout components:
+all_done=
+while [ -z "$all_done" ] ; do
+    # Cycle through all components and find one that can be mounted.
+    willdodev=
+    willdotype=
+
+    cp "$LAYOUT_TODO" "${LAYOUT_TODO}.tmp"
+    while read status thisdev type; do
+        # Test if all dependencies are already created.
+        Debug "Testing $thisdev for dependencies..."
+        deps=($(grep "^$thisdev\ " "$LAYOUT_DEPS" | cut -d " " -f "2"))
+        Debug "deps (${#deps[@]}): ${deps[*]}"
+
+        donedeps=0
+        for dep in "${deps[@]}" ; do
+            if grep -q "done $dep " "$LAYOUT_TODO.tmp"; then
+                let donedeps++
+            fi
+        done
+
+        if [ ${#deps[@]} -eq $donedeps ] ; then
+            Debug "All dependencies for $thisdev are present, processing..."
+            willdodev="$thisdev"
+            willdotype="$type"
+            break
+        fi
+    done < <(grep "^todo" "$LAYOUT_TODO")
+    rm "$LAYOUT_TODO.tmp"
+
+    # Write the code to mount a device.
+    if [ -n "$willdodev" ] ; then
+        do_mount_device "$willdodev" "$willdotype"
+
+        mark_as_done "$willdodev"
+    else
+        # No device to be mounted, no additional dependencies can be satisfied.
+        all_done="y"
+    fi
+
+done

usr/share/rear/layout/prep-for-mount/default/550_finalize_script.sh

@@ -0,0 +1,10 @@
+# Add final information to the script.
+
+cat >> $LAYOUT_CODE <<EOF
+
+set +x
+set +e
+
+LogPrint "Disk layout processed."
+
+EOF

usr/share/rear/layout/prep-for-mount/default/600_show_unprocessed.sh

@@ -0,0 +1,58 @@
+
+# Warn about missing components and for each missing component
+# offer the user a way to manually add code that mounts it.
+
+rear_workflow="rear $WORKFLOW"
+rear_shell_history="$( echo -e "vi $LAYOUT_CODE\nless $LAYOUT_CODE" )"
+
+unset choices
+choices[0]="View $LAYOUT_CODE"
+choices[1]="Edit $LAYOUT_CODE"
+choices[2]="Go to Relax-and-Recover shell"
+choices[3]="Continue '$rear_workflow'"
+choices[4]="Abort '$rear_workflow'"
+
+while read status name type junk ; do
+    missing_component="$name ($type)"
+    LogUserOutput "No code has been generated to mount $missing_component."
+    LogUserOutput "To mount $missing_component manually add code to $LAYOUT_CODE or abort."
+    while true ; do
+        # The default user input is "Continue" to make it possible to run ReaR unattended
+        # so that 'rear mountonly' proceeds after the timeout regardless that it probably fails
+        # when the component is not recreated but perhaps it could succeed in migration mode
+        # on different replacement hardware where it might be even right to simply "Continue".
+        # Generate a runtime-specific user_input_ID so that for each missing component
+        # a different user_input_ID is used for the UserInput call so that the user can specify
+        # for each missing component a different predefined user input.
+        # Only uppercase letters and digits are used to ensure the user_input_ID is a valid bash variable name
+        # (otherwise the UserInput call could become invalid which aborts 'rear mountonly' with a BugError) and
+        # hopefully only uppercase letters and digits are sufficient to distinguish different missing components:
+        current_missing_component_alnum_uppercase="$( echo "$missing_component" | tr -d -c '[:alnum:]' | tr '[:lower:]' '[:upper:]' )"
+        test "$current_missing_component_alnum_uppercase" || current_missing_component_alnum_uppercase="COMPONENT"
+        user_input_ID="ADD_CODE_TO_RECREATE_MISSING_$current_missing_component_alnum_uppercase"
+        case "$( UserInput -I $user_input_ID -p "Manually add code that mounts $missing_component" -D "${choices[3]}" "${choices[@]}" )" in
+            (${choices[0]})
+                # Run 'less' with the original STDIN STDOUT and STDERR when 'rear' was launched by the user:
+                less $LAYOUT_CODE 0<&6 1>&7 2>&8
+                ;;
+            (${choices[1]})
+                # Run 'vi' with the original STDIN STDOUT and STDERR when 'rear' was launched by the user:
+                vi $LAYOUT_CODE 0<&6 1>&7 2>&8
+                ;;
+            (${choices[2]})
+                # rear_shell runs 'bash' with the original STDIN STDOUT and STDERR when 'rear' was launched by the user:
+                rear_shell "" "$rear_shell_history"
+                ;;
+            (${choices[3]})
+                # Continue with the next missing component:
+                break
+                ;;
+            (${choices[4]})
+                abort_recreate
+                Error "User chose to abort '$rear_workflow' in ${BASH_SOURCE[0]}"
+                ;;
+            # No default case is needed here because the 'while true' loop repeats for invalid user input.
+        esac
+    done
+done < <(grep "^todo" "$LAYOUT_TODO")
+