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>

4 files changed, 39 insertions, 8 deletions

diff --git a/archinstall/lib/installer.py b/archinstall/lib/installer.py
index 2a7b158a..257dda22 100644
--- a/archinstall/lib/installer.py
+++ b/archinstall/lib/installer.py
@@ -30,6 +30,8 @@ __packages__ = ["base", "base-devel", "linux-firmware", "linux", "linux-lts", "l
 # Additional packages that are installed if the user is running the Live ISO with accessibility tools enabled
 __accessibility_packages__ = ["brltty", "espeakup", "alsa-utils"]
 
+from .pacman import run_pacman
+
 
 class InstallationFile:
 	def __init__(self, installation :'Installer', filename :str, owner :str, mode :str = "w"):
@@ -292,7 +294,7 @@ class Installer:
 	def enable_multilib_repository(self):
 		# Set up a regular expression pattern of a commented line containing 'multilib' within []
 		pattern = re.compile("^#\\[.*multilib.*\\]$")
-		
+
 		# This is used to track if the previous line is a match, so we end up uncommenting the line after the block.
 		matched = False
 
@@ -318,7 +320,7 @@ class Installer:
 	def enable_testing_repositories(self, enable_multilib_testing=False):
 		# Set up a regular expression pattern of a commented line containing 'testing' within []
 		pattern = re.compile("^#\\[.*testing.*\\]$")
-		
+
 		# This is used to track if the previous line is a match, so we end up uncommenting the line after the block.
 		matched = False
 
@@ -352,7 +354,7 @@ class Installer:
 
 		self.log(f'Installing packages: {packages}', level=logging.INFO)
 
-		if (sync_mirrors := SysCommand('/usr/bin/pacman -Syy')).exit_code == 0:
+		if (sync_mirrors := run_pacman('-Syy', default_cmd='/usr/bin/pacman')).exit_code == 0:
 			if (pacstrap := SysCommand(f'/usr/bin/pacstrap -C /etc/pacman.conf {self.target} {" ".join(packages)} --noconfirm', peak_output=True)).exit_code == 0:
 				return True
 			else:
diff --git a/archinstall/lib/networking.py b/archinstall/lib/networking.py
index 5331216c..3e883a7b 100644
--- a/archinstall/lib/networking.py
+++ b/archinstall/lib/networking.py
@@ -7,6 +7,7 @@ from typing import Union, Dict, Any, List
 from .exceptions import HardwareIncompatibilityError
 from .general import SysCommand
 from .output import log
+from .pacman import run_pacman
 from .storage import storage
 
 
@@ -32,7 +33,7 @@ def list_interfaces(skip_loopback :bool = True) -> Dict[str, str]:
 
 def check_mirror_reachable() -> bool:
 	log("Testing connectivity to the Arch Linux mirrors ...", level=logging.INFO)
-	if SysCommand("pacman -Sy").exit_code == 0:
+	if run_pacman("-Sy").exit_code == 0:
 		return True
 
 	elif os.geteuid() != 0:
@@ -42,9 +43,9 @@ def check_mirror_reachable() -> bool:
 
 def update_keyring() -> bool:
 	log("Updating archlinux-keyring ...", level=logging.INFO)
-	if SysCommand("pacman -Sy --noconfirm archlinux-keyring").exit_code == 0:
+	if run_pacman("-Sy --noconfirm archlinux-keyring").exit_code == 0:
 		return True
-	
+
 	elif os.geteuid() != 0:
 		log("update_keyring() uses 'pacman -Sy archlinux-keyring' which requires root.", level=logging.ERROR, fg="red")
 
diff --git a/archinstall/lib/packages/packages.py b/archinstall/lib/packages/packages.py
index 26d8ff68..b2c8ab8e 100644
--- a/archinstall/lib/packages/packages.py
+++ b/archinstall/lib/packages/packages.py
@@ -4,8 +4,8 @@ import urllib.request
 from typing import Dict, Any, Tuple, List
 
 from ..exceptions import PackageError, SysCallError
-from ..general import SysCommand
 from ..models.dataclasses import PackageSearch, PackageSearchResult, LocalPackage
+from ..pacman import run_pacman
 
 BASE_URL_PKG_SEARCH = 'https://archlinux.org/packages/search/json/?name={package}'
 # BASE_URL_PKG_CONTENT = 'https://archlinux.org/packages/search/json/'
@@ -98,7 +98,7 @@ def validate_package_list(packages :list) -> Tuple[list, list]:
 def installed_package(package :str) -> LocalPackage:
 	package_info = {}
 	try:
-		for line in SysCommand(f"pacman -Q --info {package}"):
+		for line in run_pacman(f"-Q --info {package}"):
 			if b':' in line:
 				key, value = line.decode().split(':', 1)
 				package_info[key.strip().lower().replace(' ', '_')] = value.strip()
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}')