support for read only /boot mount

Support is added for greenboot to work with read-only /boot.
It uses PrivateMounts=yes to isolate the system and remounts
boot as rw followed by setting the grub parameters as per healthcheck.

The following services are affected:

greenboot-grub2-set-success.service
greenboot-grub2-set-counter.service
greenboot-rpm-ostree-check-fallback.service

The grub2-editenv command is decoupled from greenboot-grub2-set-success.service
and is part of a separate script.

Signed-off-by: saypaul <paul.sayan@gmail.com>

greenboot.spec

@@ -154,6 +154,7 @@ install -DpZm 0644 etc/greenboot/greenboot.conf %{buildroot}%{_sysconfdir}/%{nam
 %{_prefix}/lib/bootupd/grub2-static/configs.d/*.cfg
 %{_unitdir}/greenboot-status.service
 %{_libexecdir}/%{name}/greenboot-grub2-set-counter
+%{_libexecdir}/%{name}/greenboot-grub2-set-success
 %{_unitdir}/greenboot-grub2-set-success.service
 %{_unitdir}/greenboot-grub2-set-counter.service
 %{_libexecdir}/%{name}/greenboot-rpm-ostree-grub2-check-fallback

usr/lib/systemd/system/greenboot-grub2-set-counter.service

@@ -18,6 +18,7 @@ RequiresMountsFor=/boot
 Type=oneshot
 RemainAfterExit=yes
 ExecStart=/usr/libexec/greenboot/greenboot-grub2-set-counter
+PrivateMounts=yes
 
 [Install]
 RequiredBy=ostree-finalize-staged.service

usr/lib/systemd/system/greenboot-grub2-set-success.service

@@ -15,8 +15,8 @@ After=boot-complete.target
 [Service]
 Type=oneshot
 RemainAfterExit=yes
-ExecStart=/usr/bin/grub2-editenv - set boot_success=1
-ExecStart=/usr/bin/grub2-editenv - unset boot_counter
+ExecStart=/usr/libexec/greenboot/greenboot-grub2-set-success
+PrivateMounts=yes
 
 [Install]
 WantedBy=multi-user.target

usr/lib/systemd/system/greenboot-rpm-ostree-grub2-check-fallback.service

@@ -16,6 +16,7 @@ Before=greenboot-grub2-set-success.service
 Type=oneshot
 RemainAfterExit=yes
 ExecStart=/usr/libexec/greenboot/greenboot-rpm-ostree-grub2-check-fallback
+PrivateMounts=yes
 
 [Install]
 RequiredBy=greenboot-healthcheck.service

usr/libexec/greenboot/greenboot-grub2-set-counter

@@ -1,6 +1,13 @@
 #!/bin/bash
 set -eo pipefail
 
+function remount_boot_ro {
+    if grep -q " /boot .* rw," /proc/mounts; then
+        mount -o remount,ro /boot || exit 5
+    fi
+    return
+}
+
 GREENBOOT_CONFIGURATION_FILE=/etc/greenboot/greenboot.conf
 if test -f "$GREENBOOT_CONFIGURATION_FILE"; then
     # shellcheck source=etc/greenboot/greenboot.conf
@@ -14,7 +21,25 @@ elif [ -n "$GREENBOOT_MAX_BOOT_ATTEMPTS" ]; then
 else
     max_boot_attempts=3 # default to 3 attempts
 fi
-grub2-editenv - set boot_counter="$max_boot_attempts"
-grub2-editenv - set boot_success=0
+
+# Remount /boot as read-only if it was mounted as read-write
+if grep -q " /boot .* rw," /proc/mounts; then
+    mount -o remount,ro /boot || exit 5
+fi
+
+if ! /usr/bin/grub2-editenv - set boot_counter="$max_boot_attempts"; then
+ # If the first command fails, remount /boot as read-only and exit with failure
+    remount_boot_ro
+    exit 1
+fi
+
+if ! /usr/bin/grub2-editenv /boot/grub2/grubenv set boot_success=0; then
+    # If the first command fails, remount /boot as read-only and exit with failure
+    remount_boot_ro
+    exit 1
+fi
+
+# Revert /boot as read-only
+remount_boot_ro
 
 echo "<3>GRUB2 environment variables have been set for system upgrade. Max boot attempts is $max_boot_attempts"

usr/libexec/greenboot/greenboot-grub2-set-success

@@ -0,0 +1,34 @@
+#!/bin/bash
+
+set -eo pipefail
+
+function remount_boot_ro {
+    if grep -q " /boot .* rw," /proc/mounts; then
+        mount -o remount,ro /boot || exit 5
+    fi
+    return
+}
+
+# Check if /boot is mounted as read-only, and remount as read-write if necessary
+if grep -q " /boot .* ro," /proc/mounts; then
+    mount -o remount,rw /boot || exit 5
+fi
+
+# Run the grub2-editenv commands
+if ! /usr/bin/grub2-editenv /boot/grub2/grubenv set boot_success=1; then
+    # If the first command fails, remount /boot as read-only and exit with failure
+    remount_boot_ro
+    exit 1
+fi
+
+if ! /usr/bin/grub2-editenv /boot/grubenv unset boot_counter; then
+    # If the second command fails, remount /boot as read-only and exit with failure
+    remount_boot_ro
+    exit 1
+fi
+
+# Remount /boot as read-only if it was mounted as read-write
+remount_boot_ro
+
+# If everything succeeded, exit with success
+exit 0

usr/libexec/greenboot/greenboot-rpm-ostree-grub2-check-fallback

@@ -1,6 +1,13 @@
 #!/bin/bash
 set -euo pipefail
 
+function remount_boot_ro {
+    if grep -q " /boot .* rw," /proc/mounts; then
+        mount -o remount,ro /boot || exit 5
+    fi
+    return
+}
+
 # Determine if the current boot is a fallback boot
 # If booted into fallback deployment, clean up bootloader entries (rollback)
 if grub2-editenv list | grep -q "^boot_counter=-1$"; then
@@ -12,5 +19,19 @@ if grub2-editenv list | grep -q "^boot_counter=-1$"; then
     echo "<3>Health check logs from previous boot:"
     echo "<3>$prev_logs"
   fi
-  grub2-editenv - unset boot_counter
+
+
+  # Check if /boot is mounted as read-only, and remount as read-write if necessary
+  if grep -q " /boot .* ro," /proc/mounts; then
+      mount -o remount,rw /boot || exit 5
+  fi
+
+  if ! /usr/bin/grub2-editenv - unset boot_counter; then
+    # If the above command fails, remount /boot as read-only and exit with failure
+    remount_boot_ro
+    exit 1
+  fi
 fi
+
+# Remount /boot as read-only if it was mounted as read-write
+remount_boot_ro