Check if pacman is available (#958)

* Check if pacman is available

* Update pacman call

* Added a graceful wait to `run_pacman`

* Fix flake8

Co-authored-by: Daniel Girtler <girtler.daniel@gmail.com>
Co-authored-by: Anton Hvornum <anton.feeds+github@gmail.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/archinstall/lib/pacman.py b/archinstall/lib/pacman.py
new file mode 100644
index 00000000..9c427aff
--- /dev/null
+++ b/archinstall/lib/pacman.py
@@ -0,0 +1,28 @@
+import logging
+import pathlib
+import time
+
+from .general import SysCommand
+from .output import log
+
+
+def run_pacman(args :str, default_cmd :str = 'pacman') -> SysCommand:
+	"""
+	A centralized function to call `pacman` from.
+	It also protects us from colliding with other running pacman sessions (if used locally).
+	The grace period is set to 10 minutes before exiting hard if another pacman instance is running.
+	"""
+	pacman_db_lock = pathlib.Path('/var/lib/pacman/db.lck')
+
+	if pacman_db_lock.exists():
+		log(_('Pacman is already running, waiting maximum 10 minutes for it to terminate.'), level=logging.WARNING, fg="red")
+
+	started = time.time()
+	while pacman_db_lock.exists():
+		time.sleep(0.25)
+
+		if time.time() - started > (60 * 10):
+			log(_('Pre-existing pacman lock never exited. Please clean up any existing pacman sessions before using archinstall.'), level=logging.WARNING, fg="red")
+			exit(1)
+
+	return SysCommand(f'{default_cmd} {args}')