Move the .uuid file to /boot/grub/YYYY-mm-dd-HH-MM-SS-00.uuid

To prevent the file from being accidentally missed when someone copies
the ISO's contents, let's not place it in a directory that starts with a
dot. Since all GRUB related files are in /boot/grub/, put it there too.

Instead of using a more unique UUID for the file name, use
`YYYY-mm-dd-HH-MM-SS-00.uuid` which matches the ISO's modification date
in UTC,i.e. its "UUID". If multiple ISOs would be generated in the exact
same second, the ISO 9660 modification date (i.e. its "UUID") would be
the same, so there would be not way to distinguish between the volumes
anyway. This also makes the file look less suspicious to the casual
glance.

CHANGELOG.rst

@@ -10,7 +10,7 @@ Added
 
 - Support *file system transposition* to simplify boot medium preparation for UEFI boot via extracting the ISO image
   contents to a drive. ``grub.cfg`` does not hardcode the ISO volume label anymore, instead GRUB will search for volume
-  with a ``/.disk/%UUID_SEARCH_FILENAME%.uuid`` file on it.
+  with a ``/boot/grub/YYYY-mm-dd-HH-MM-SS-00.uuid`` file on it.
 - Preload GRUB's NTFS modules for UEFI that allegedly have native NTFS support. GRUB's exFAT and UDF modules are also
   preloaded in case someone finds them useful.
 

archiso/mkarchiso

@@ -558,22 +558,24 @@ _make_common_bootmode_grub_copy_to_isofs() {
 
 # Prepare GRUB configuration files
 _make_common_bootmode_grub_cfg(){
-    local _cfg uuid_search_filename
+    local _cfg archiso_uuid search_filename
-
-    # Create a .uuid file and place it in /.disk/ on ISO 9660 to provide a way for GRUB to search for the volume
-    uuid_search_filename="$(uuidgen --sha1 --namespace 93a870ff-8565-4cf3-a67b-f47299271a96 \
-        --name "${SOURCE_DATE_EPOCH} disk search UUID")"
-    install -d -m 0755 -- "${isofs_dir}/.disk"
-    : > "${isofs_dir}/.disk/${uuid_search_filename}.uuid"
 
     install -d -- "${work_dir}/grub"
 
+    # Precalculate the ISO's modification date in UTC, i.e. its "UUID"
+    TZ=UTC printf -v archiso_uuid '%(%F-%H-%M-%S-00)T' "$SOURCE_DATE_EPOCH"
+    # Create a /boot/grub/YYYY-mm-dd-HH-MM-SS-00.uuid file on ISO 9660. GRUB will search for it to find the ISO
+    # volume. This is similar to what grub-mkrescue does, except it places the file in /.disk/, but we opt to use a
+    # directory that does not start with a dot to avoid it being accidentally missed when copying the ISO's contents.
+    : > "${work_dir}/grub/${archiso_uuid}.uuid"
+    search_filename="/boot/grub/${archiso_uuid}.uuid"
+
     # Fill GRUB configuration files
     for _cfg in "${profile}/grub/"*'.cfg'; do
         sed "s|%ARCHISO_LABEL%|${iso_label}|g;
              s|%INSTALL_DIR%|${install_dir}|g;
              s|%ARCH%|${arch}|g;
-             s|%UUID_SEARCH_FILENAME%|${uuid_search_filename}|g" \
+             s|%ARCHISO_SEARCH_FILENAME%|${search_filename}|g" \
              "${_cfg}" > "${work_dir}/grub/${_cfg##*/}"
     done
 
@@ -596,13 +598,13 @@ if [ -z "${ARCHISO_HINT}" ]; then
 fi
 
 # Search for the ISO volume
-if search --no-floppy --set=archiso_device --file '/.disk/%UUID_SEARCH_FILENAME%.uuid' --hint "${ARCHISO_HINT}"; then
+if search --no-floppy --set=archiso_device --file '%ARCHISO_SEARCH_FILENAME%' --hint "${ARCHISO_HINT}"; then
     set ARCHISO_HINT="${archiso_device}"
     if probe --set ARCHISO_UUID --fs-uuid "${ARCHISO_HINT}"; then
         export ARCHISO_UUID
     fi
 else
-    echo "Could not find a volume with a '/.disk/%UUID_SEARCH_FILENAME%.uuid' file on it!"
+    echo "Could not find a volume with a '%ARCHISO_SEARCH_FILENAME%' file on it!"
 fi
 
 # Load grub.cfg
@@ -616,18 +618,18 @@ else
     echo "File '(${ARCHISO_HINT})/boot/grub/grub.cfg' not found!"
 fi
 EOF
-    grubembedcfg="${grubembedcfg//'%UUID_SEARCH_FILENAME%'/"${uuid_search_filename}"}"
+    grubembedcfg="${grubembedcfg//'%ARCHISO_SEARCH_FILENAME%'/"${search_filename}"}"
     printf '%s\n' "$grubembedcfg" > "${work_dir}/grub-embed.cfg"
 
     # Write grubenv
     printf '%.1024s' \
-        "$(printf '# GRUB Environment Block\nNAME=%s\nVERSION=%s\nARCHISO_LABEL=%s\nINSTALL_DIR=%s\nARCH=%s\nUUID_SEARCH_FILENAME=%s\n%s' \
+        "$(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}" \
             "${arch}" \
-            "${uuid_search_filename}" \
+            "${search_filename}" \
             "$(printf '%0.1s' "#"{1..1024})")" \
         > "${work_dir}/grub/grubenv"
 }

configs/baseline/grub/grub.cfg

@@ -29,7 +29,7 @@ if [ -z "${ARCHISO_UUID}" ]; then
     if [ -z "${ARCHISO_HINT}" ]; then
         regexp --set=1:ARCHISO_HINT '^\(([^)]+)\)' "${cmdpath}"
     fi
-    search --no-floppy --set=root --file '/.disk/%UUID_SEARCH_FILENAME%.uuid' --hint "${ARCHISO_HINT}"
+    search --no-floppy --set=root --file '%ARCHISO_SEARCH_FILENAME%' --hint "${ARCHISO_HINT}"
     probe --set ARCHISO_UUID --fs-uuid "${root}"
 fi
 

configs/releng/grub/grub.cfg

@@ -29,7 +29,7 @@ if [ -z "${ARCHISO_UUID}" ]; then
     if [ -z "${ARCHISO_HINT}" ]; then
         regexp --set=1:ARCHISO_HINT '^\(([^)]+)\)' "${cmdpath}"
     fi
-    search --no-floppy --set=root --file '/.disk/%UUID_SEARCH_FILENAME%.uuid' --hint "${ARCHISO_HINT}"
+    search --no-floppy --set=root --file '%ARCHISO_SEARCH_FILENAME%' --hint "${ARCHISO_HINT}"
     probe --set ARCHISO_UUID --fs-uuid "${root}"
 fi