refactor: extract EFI_DIR constant for the install-time EFI mount point

The literal /mnt/efi appeared at 17 sites across installer/archangel and installer/lib/btrfs.sh. Renaming it (or pointing tests at a different mount) meant touching every site and risking incomplete sweeps. One canonical name in installer/lib/common.sh now backs every reference.

EFI_DIR has no trailing slash so the three expansion patterns in the codebase compose cleanly. Bare ($EFI_DIR), sub-path ($EFI_DIR/EFI/ZBM), and the index-suffix used by install_grub_all_efi for secondary EFI mounts (${EFI_DIR}${i}). The sync_efi_partitions staging path also moves from the literal /mnt/efi_sync to ${EFI_DIR}_sync, so it follows EFI_DIR if anyone ever changes the base.

Two follow-ups filed as separate :techdebt: items. MNTPOINT=/mnt extraction across the 50+ /mnt/... sites (pacstrap, arch-chroot, fstab writes), and the related /mnt${chroot_efi_dir} composition pattern at btrfs.sh:681-682. Both ship together when MNTPOINT lands.

Verified: bats 134 → 135 (+1 pinning EFI_DIR=/mnt/efi). Lint clean. All four expansion patterns smoke-tested at runtime and produce the original literal byte-for-byte. VM run skipped, pure constant substitution with zero behavior change.

4 files changed, 36 insertions, 18 deletions

diff --git a/installer/archangel b/installer/archangel
index 10ec68a..64718da 100755
--- a/installer/archangel
+++ b/installer/archangel
@@ -729,9 +729,9 @@ mount_efi() {
     step "Mounting EFI Partition"
     # EFI partition mounts at /efi - only holds ZFSBootMenu binary
     # /boot is a directory on ZFS root (kernels live on ZFS for snapshot safety)
-    mkdir -p /mnt/efi
-    mount "${EFI_PARTS[0]}" /mnt/efi
-    info "EFI partition ${EFI_PARTS[0]} mounted at /mnt/efi"
+    mkdir -p $EFI_DIR
+    mount "${EFI_PARTS[0]}" $EFI_DIR
+    info "EFI partition ${EFI_PARTS[0]} mounted at $EFI_DIR"
 }
 
 install_base() {
@@ -964,13 +964,13 @@ configure_zfsbootmenu() {
     cp /etc/hostid /mnt/etc/hostid
 
     # Create ZFSBootMenu directory on EFI
-    mkdir -p /mnt/efi/EFI/ZBM
+    mkdir -p $EFI_DIR/EFI/ZBM
 
     # Download ZFSBootMenu release EFI binary
     # Using the bundled release which includes everything needed
     info "Downloading ZFSBootMenu..."
     local zbm_url="https://get.zfsbootmenu.org/efi"
-    if ! curl -fsSL -o /mnt/efi/EFI/ZBM/zfsbootmenu.efi "$zbm_url"; then
+    if ! curl -fsSL -o $EFI_DIR/EFI/ZBM/zfsbootmenu.efi "$zbm_url"; then
         error "Failed to download ZFSBootMenu"
     fi
     info "ZFSBootMenu binary installed."
@@ -1163,7 +1163,7 @@ sync_efi_partitions() {
 
     step "Syncing EFI Partitions for Redundancy"
 
-    local temp_mount="/mnt/efi_sync"
+    local temp_mount="${EFI_DIR}_sync"
 
     for i in "${!EFI_PARTS[@]}"; do
         if [[ $i -eq 0 ]]; then
@@ -1178,7 +1178,7 @@ sync_efi_partitions() {
 
         # Copy ZFSBootMenu binary to secondary EFI partitions
         mkdir -p "$temp_mount/EFI/ZBM"
-        cp /mnt/efi/EFI/ZBM/zfsbootmenu.efi "$temp_mount/EFI/ZBM/"
+        cp $EFI_DIR/EFI/ZBM/zfsbootmenu.efi "$temp_mount/EFI/ZBM/"
 
         umount "$temp_mount"
     done
@@ -1257,7 +1257,7 @@ cleanup() {
     ZFS_PASSPHRASE=""
 
     info "Unmounting filesystems..."
-    umount /mnt/efi 2>/dev/null || true
+    umount $EFI_DIR 2>/dev/null || true
 
     info "Exporting ZFS pool..."
     zpool export "$POOL_NAME"
@@ -1285,7 +1285,7 @@ install_failure_cleanup() {
 
     case "$FILESYSTEM" in
         zfs)
-            umount /mnt/efi 2>/dev/null || true
+            umount $EFI_DIR 2>/dev/null || true
             umount -R /mnt 2>/dev/null || true
             if zpool list "$POOL_NAME" >/dev/null 2>&1; then
                 zpool export "$POOL_NAME" 2>/dev/null \
@@ -1294,7 +1294,7 @@ install_failure_cleanup() {
             fi
             ;;
         btrfs)
-            umount /mnt/efi 2>/dev/null || true
+            umount $EFI_DIR 2>/dev/null || true
             btrfs_cleanup 2>/dev/null || true
             btrfs_close_encryption 2>/dev/null || true
             ;;
@@ -1461,8 +1461,8 @@ install_btrfs() {
     btrfs_make_filesystem     btrfs_devices
     create_btrfs_subvolumes   "${btrfs_devices[0]}"
     mount_btrfs_subvolumes    "${btrfs_devices[0]}"
-    mkdir -p /mnt/efi
-    mount "${EFI_PARTS[0]}" /mnt/efi
+    mkdir -p $EFI_DIR
+    mount "${EFI_PARTS[0]}" $EFI_DIR
 
     # Base install + system config
     install_base
diff --git a/installer/lib/btrfs.sh b/installer/lib/btrfs.sh
index f1cfaac..09127b2 100644
--- a/installer/lib/btrfs.sh
+++ b/installer/lib/btrfs.sh
@@ -567,8 +567,8 @@ configure_grub() {
     step "Configuring GRUB Bootloader"
 
     # Mount EFI partition
-    mkdir -p /mnt/efi
-    mount "$efi_partition" /mnt/efi
+    mkdir -p $EFI_DIR
+    mount "$efi_partition" $EFI_DIR
 
     # Configure GRUB defaults for btrfs
     info "Setting GRUB configuration..."
@@ -624,7 +624,7 @@ EOF
 
     # Create grub directory on EFI partition
     # GRUB modules on FAT32 EFI partition avoid btrfs subvolume path issues
-    mkdir -p /mnt/efi/grub
+    mkdir -p $EFI_DIR/grub
 
     # Install GRUB with boot-directory on EFI partition
     info "Installing GRUB to EFI partition..."
@@ -665,12 +665,12 @@ install_grub_all_efi() {
     for efi_part in "${efi_partitions[@]}"; do
         # First EFI at /efi (already mounted), subsequent at /efi2, /efi3, etc.
         local chroot_efi_dir="/efi"
-        local mount_point="/mnt/efi"
+        local mount_point="$EFI_DIR"
         local bootloader_id="GRUB"
 
         if [[ $i -gt 1 ]]; then
             chroot_efi_dir="/efi${i}"
-            mount_point="/mnt/efi${i}"
+            mount_point="$EFI_DIR${i}"
             bootloader_id="GRUB-disk${i}"
 
             # Mount secondary EFI partitions
@@ -887,7 +887,7 @@ btrfs_cleanup() {
     sync
 
     # Unmount EFI first
-    umount /mnt/efi 2>/dev/null || true
+    umount $EFI_DIR 2>/dev/null || true
 
     # Unmount all btrfs subvolumes (reverse order)
     for ((i=${#BTRFS_SUBVOLS[@]}-1; i>=0; i--)); do
diff --git a/installer/lib/common.sh b/installer/lib/common.sh
index 98220fa..d375a9c 100644
--- a/installer/lib/common.sh
+++ b/installer/lib/common.sh
@@ -3,6 +3,16 @@
 # Source this file: source "$(dirname "$0")/lib/common.sh"
 
 #############################
+# Path Constants
+#############################
+
+# Mount point for the primary EFI partition during install. Sub-paths
+# compose with ${EFI_DIR}/...; secondary EFI partitions in multi-disk
+# layouts use ${EFI_DIR}${i} (no trailing slash, so the index appends
+# cleanly).
+EFI_DIR="/mnt/efi"
+
+#############################
 # Output Functions
 #############################
 
diff --git a/tests/unit/test_common.bats b/tests/unit/test_common.bats
index 0bb76a1..4d58bd9 100644
--- a/tests/unit/test_common.bats
+++ b/tests/unit/test_common.bats
@@ -324,3 +324,11 @@ Boot0001* ZFSBootMenu"
     [ "$status" -eq 1 ]
     [ -z "$output" ]
 }
+
+#############################
+# Path constants
+#############################
+
+@test "EFI_DIR is defined and equals /mnt/efi" {
+    [ "$EFI_DIR" = "/mnt/efi" ]
+}