configs/*/grub/grub.cfg: search for a .uuid file in /.disk/ and use the volume it's on

Search for `/.disk/%UUID_SEARCH_FILENAME%.uuid` and pass the UUID of the
volume it's on as `archisodevice`. mkarchiso will replace
`%UUID_SEARCH_FILENAME%` with a hardcoded value generated using
`SOURCE_DATE_EPOCH` durring ISO build.

This allows to prepare an UEFI bootable installation medium by simply
copying the directory structure without having to touch `grub.cfg`.

Relying on the volume UUID instead of its LABEL also avoids collisions
of multiple ISOs created in the same month.

Fixes #202

1 files changed, 6 insertions, 2 deletions

diff --git a/configs/baseline/grub/grub.cfg b/configs/baseline/grub/grub.cfg
index d2aa4ab..7d73fe6 100644
--- a/configs/baseline/grub/grub.cfg
+++ b/configs/baseline/grub/grub.cfg
@@ -20,6 +20,11 @@ if serial --unit=0 --speed=115200; then
     terminal_output --append serial
 fi
 
+# Search for the ISO volume
+regexp --set=1:ARCHISO_HINT '^\(([^)]+)\)' "${cmdpath}"
+search --no-floppy --set=root --file '/.disk/%UUID_SEARCH_FILENAME%.uuid' --hint "${ARCHISO_HINT}"
+probe --set ARCHISO_UUID --fs-uuid "${root}"
+
 # Set default menu entry
 default=archlinux
 timeout=15
@@ -30,7 +35,6 @@ timeout_style=menu
 
 menuentry "Arch Linux (x86_64, UEFI)" --class arch --class gnu-linux --class gnu --class os --id 'archlinux' {
     set gfxpayload=keep
-    search --no-floppy --set=root --label %ARCHISO_LABEL%
-    linux /%INSTALL_DIR%/boot/x86_64/vmlinuz-linux archisobasedir=%INSTALL_DIR% archisolabel=%ARCHISO_LABEL%
+    linux /%INSTALL_DIR%/boot/x86_64/vmlinuz-linux archisobasedir=%INSTALL_DIR% archisodevice=/dev/disk/by-uuid/${ARCHISO_UUID}
     initrd /%INSTALL_DIR%/boot/x86_64/initramfs-linux.img
 }