uefi: define EFIBOOTMGR_BIN to ease changing the efibootmgr binary

The json functionality proposed upstream might be merged one day
in efibootmgr so deploying a fork would not be needed anymore.
This change aims to ease the migration once that day comes.

src/utils/uefi.py

@@ -14,6 +14,8 @@ import subprocess
 
 import fdisk
 
+EFIBOOTMGR_BIN='efibootmgr-json'
+
 def _find_bootentry(entries, label):
     for entry in entries:
         if entry['description'] == label:
@@ -37,7 +39,7 @@ def _check_efibootmgr_json():
     """
     supported = True
     try:
-        subprocess.run(['efibootmgr-json', '--json'], stdout=subprocess.DEVNULL,
+        subprocess.run([EFIBOOTMGR_BIN, '--json'], stdout=subprocess.DEVNULL,
                        stderr=subprocess.DEVNULL, check=True)
     except subprocess.CalledProcessError:
         supported = False
@@ -50,9 +52,9 @@ def is_uefi_supported():
 
 def run_efibootmgr_json():
     if _check_efibootmgr_json() is False:
-        raise RuntimeError('efibootmgr-json not available')
+        raise RuntimeError(f'{EFIBOOTMGR_BIN} not available')
 
-    proc = subprocess.run(['efibootmgr-json', '--json'], capture_output=True, text=True)
+    proc = subprocess.run([EFIBOOTMGR_BIN, '--json'], capture_output=True, text=True)
     dict_json = json.loads(proc.stdout)
 
     return dict_json
@@ -60,24 +62,24 @@ def run_efibootmgr_json():
 
 def efibootmgr_bootnext(description):
     logging.info(f'Setting BootNext to value from boot entry with label {description}')
-    bootnext_cmd = 'efibootmgr-json -n {bootnum}'
+    bootnext_cmd = '{efibootmgr} -n {bootnum}'
     boot_entries = run_efibootmgr_json().get('vars', [])
 
     entry = _find_bootentry(boot_entries, description)
     num = _strip_boot_prefix(entry)  # efibootmgr output uses BootXXXX for each entry, remove the "Boot" prefix.
-    bootnext_cmd = bootnext_cmd.format(bootnum=num)
+    bootnext_cmd = bootnext_cmd.format(bootnum=num, efibootmgr=EFIBOOTMGR_BIN)
     subprocess.run(shlex.split(bootnext_cmd), check=True,
                    stdout=subprocess.DEVNULL)
 
 
 def efibootmgr_delete_bootentry(label):
     dict_json = run_efibootmgr_json()
-    efibootmgr_cmd = 'efibootmgr-json -q -b {bootnum} -B'
+    efibootmgr_cmd = '{efibootmgr} -q -b {bootnum} -B'
 
     for entry in dict_json.get('vars', []):
         if entry['description'] == label:
             num = entry['name'][4:]  # Remove "Boot" prefix to extract num
-            efibootmgr_cmd = efibootmgr_cmd.format(bootnum=num)
+            efibootmgr_cmd = efibootmgr_cmd.format(bootnum=num, efibootmgr=EFIBOOTMGR_BIN)
             subprocess.run(shlex.split(efibootmgr_cmd), check=True)
             break
     else:
@@ -88,8 +90,8 @@ def efibootmgr_create_bootentry(disk, part, loader, label, add_to_bootorder=True
     entries = run_efibootmgr_json().get('vars', [])
     create_opt = '-c' if add_to_bootorder else '-C'
     index_opt = f'-I {len(entries)}'  # Requires efibootmgr version 18
-    efibootmgr_cmd = f'efibootmgr-json {create_opt} {index_opt} -d {disk} -p {part} -L {label} -l {loader}'
+    efibootmgr_cmd = f'{EFIBOOTMGR_BIN} {create_opt} {index_opt} -d {disk} -p {part} -L {label} -l {loader}'
-    logging.info(f'efibootmgr-json command creating boot entry: {efibootmgr_cmd}')
+    logging.info(f'{EFIBOOTMGR_BIN} command creating boot entry: {efibootmgr_cmd}')
     try:
         proc = subprocess.run(shlex.split(efibootmgr_cmd), check=True, text=True)
     except subprocess.CalledProcessError as e: