mkarchiso: always create /boot/grub/grubenv and /boot/grub/loopback.cfg

Even if GRUB is not used as a boot loader for the ISO, create a
`/boot/grub/grubenv` file in the ISO 9660 file system. If a
`loopback.cfg` file exists in the profile's `grub` directory, copy it
to `/boot/grub/loopback.cfg` on the ISO.

This ensures the funtionality will not be lost if the used boot loaders
are changed.

1 files changed, 41 insertions, 2 deletions

diff --git a/archiso/mkarchiso b/archiso/mkarchiso
index a727a1a..7890615 100755
--- a/archiso/mkarchiso
+++ b/archiso/mkarchiso
@@ -420,6 +420,10 @@ _make_bootmodes() {
     for bootmode in "${bootmodes[@]}"; do
         _run_once "_make_bootmode_${bootmode}"
     done
+
+    if [[ "${bootmodes[*]}" != *grub* ]]; then
+        _run_once _make_common_grubenv_and_loopbackcfg
+    fi
 }
 
 # Copy kernel and initramfs to ISO 9660
@@ -638,6 +642,40 @@ EOF
         >"${work_dir}/grub/grubenv"
 }
 
+# Create GRUB specific configuration files when GRUB is not used as a boot loader
+_make_common_grubenv_and_loopbackcfg() {
+    local search_filename
+
+    install -d -m 0755 -- "${isofs_dir}/boot/grub"
+    # Create a /boot/grub/YYYY-mm-dd-HH-MM-SS-00.uuid file on ISO 9660. GRUB will search for it to find the ISO
+    # volume. This is similar to what grub-mkrescue does, except it places the file in /.disk/, but we opt to use a
+    # directory that does not start with a dot to avoid it being accidentally missed when copying the ISO's contents.
+    search_filename="/boot/grub/${iso_uuid}.uuid"
+    : >"${isofs_dir}/${search_filename}"
+
+    # Write grubenv
+    printf '%.1024s' \
+        "$(printf '# GRUB Environment Block\nNAME=%s\nVERSION=%s\nARCHISO_LABEL=%s\nINSTALL_DIR=%s\nARCH=%s\nARCHISO_SEARCH_FILENAME=%s\n%s' \
+            "${iso_name}" \
+            "${iso_version}" \
+            "${iso_label}" \
+            "${install_dir}" \
+            "${arch}" \
+            "${search_filename}" \
+            "$(printf '%0.1s' "#"{1..1024})")" \
+        >"${isofs_dir}/boot/grub/grubenv"
+
+    # Copy loopback.cfg to /boot/grub/ on ISO 9660
+    if [[ -e "${profile}/grub/loopback.cfg" ]]; then
+        sed "s|%ARCHISO_LABEL%|${iso_label}|g;
+             s|%ARCHISO_UUID%|${iso_uuid}|g;
+             s|%INSTALL_DIR%|${install_dir}|g;
+             s|%ARCH%|${arch}|g;
+             s|%ARCHISO_SEARCH_FILENAME%|${search_filename}|g" \
+            "${profile}/grub/loopback.cfg" >"${isofs_dir}/boot/grub/loopback.cfg"
+    fi
+}
+
 _make_bootmode_uefi-ia32.grub.esp() {
     local grubmodules=()
 
@@ -1800,8 +1838,9 @@ _make_version() {
     fi
     if [[ "${buildmode}" == "iso" ]]; then
         # Write grubenv with version information to ISO 9660
-        # TODO: after sufficient time has passed, do not create this file anymore when GRUB boot modes are used.
-        #       _make_common_bootmode_grub_cfg already creates ${isofs_dir}/boot/grub/grubenv
+        # TODO: after sufficient time has passed, do not create this file anymore.
+        #       _make_common_bootmode_grub_cfg and _make_common_grubenv_and_loopbackcfg already create a
+        #       ${isofs_dir}/boot/grub/grubenv file
         rm -f -- "${isofs_dir}/${install_dir}/grubenv"
         printf '%.1024s' "$(printf '# GRUB Environment Block\nNAME=%s\nVERSION=%s\n%s' \
             "${iso_name}" "${iso_version}" "$(printf '%0.1s' "#"{1..1024})")" \