Bump version to 4.3.0

paramiko's connect had no timeout, so a server that doesn't answer
made the program hang until the OS gave up (about 2 minutes). Give up
after 15 seconds and exit with code 5.

PKGBUILD

@@ -4,7 +4,7 @@
 
 pkgname=simple_backup
 pkgdesc='Simple backup script that uses rsync to copy files'
-pkgver=4.1.6
+pkgver=4.2.0
 pkgrel=1
 url="https://git.shouldnt.work/fuxino/${pkgname}"
 arch=('any')
@@ -12,18 +12,16 @@ license=('GPL-3.0-or-later')
 makedepends=('git'
              'python-setuptools'
              'python-build'
-             'python-installer'
-             'python-wheel')
+             'python-installer')
 depends=('python>=3.10'
-         'rsync'
-         'python-dotenv')
+         'rsync')
 optdepends=('python-systemd: use systemd log'
             'python-dbus: for desktop notifications'
             'python-paramiko: for remote backup through ssh')
 conflicts=('simple_backup-git')
 source=(git+${url}?signed#tag=${pkgver})
 validpgpkeys=('7E12BC1FF3B6EDB2CD8053EB981A2B2A3BBF5514')
-sha256sums=('b3b29d9e2e1b7b949e95674d9a401e8eeb0d5f898e8450473dce94f799ee9df3')
+sha256sums=('6c674f7981e3e5222594bdb735d4fb02ca2fcc829de57ea8f92ce71e679853f9')
 
 build()
 {

README.md

@@ -20,21 +20,19 @@ The script uses rsync to actually run the backup, so you will have to install it
 sudo pacman -Syu rsync
 ```
 
-It's also required to have python-dotenv
-
-Optional dependencies are systemd-python to enable using systemd journal for logging, and dbus-python for desktop notifications.
+Optional dependencies are systemd-python to enable using systemd journal for logging, dbus-python for desktop notifications, and paramiko for remote backup.
 
 ## Install
 To install the program, first clone the repository:
 
 ```bash
-git clone https://github.com/Fuxino/simple_backup.git
+git clone https://git.shouldnt.work/fuxino/simple_backup.git
 ```
 
 Then install the tools required to build the package:
 
 ```bash
-pip install --upgrade build wheel
+pip install --upgrade build
 ```
 
 Finally, run:
@@ -49,11 +47,16 @@ For Arch Linux and Arch-based distros, two packages are available in the AUR (au
 - **simple_backup** for the release version
 - **simple_backup-git** for the git version
 
+## Old backups
+The number of old backups to keep can be set with the --keep (or -k) argument (or in the configuration file).
+Old backups are only removed if rsync completes successfully, so that they are not deleted when the new backup may be incomplete.
+The only rsync error that is ignored is return code 24 (source files vanished during the transfer), which is common when backing up a live system.
+
 ## Remote backup
 > **Warning**
 > This feature is experimental
 
-It's possible to use a remote server as destination for the backup. Just use the --username (or -u) and --host arguments (or set them in the configuration file).
+It's possible to use a remote server as destination for the backup. Just use the --ssh-user and --ssh-host arguments (or set them in the configuration file).
 For this to work, rsync must be installed on the server too.
 
 ### Server authentication

man/simple_backup.1

@@ -1,4 +1,4 @@
-.TH SIMPLE_BACKUP 1 2025-03-30 SIMPLE_BACKUP 4.1.6
+.TH SIMPLE_BACKUP 1 2026-10-08 SIMPLE_BACKUP 4.3.0
 .SH NAME
 simple_backup \- Backup files and folders using rsync
 .SH SYNOPSIS
@@ -52,7 +52,15 @@ or to use single or double quotes around them.
 .B \-o, \-\-output DIR
 Specify the directory where the files will be copied. The program will automatically
 create a subdirectory called \(aqsimple_backup\(aq (if it does not already exist) and
-inside this directory the actual backup directory (using the current date and time).
+inside this directory the actual backup directory (using the current date and time, for example
+\(aq2026\-10\-08_17\-34\-47\(aq).
+.RS
+.P
+Backups are best stored on a Linux filesystem (e.g. ext4 or btrfs). FAT and exFAT filesystems
+are supported, but they don\(aqt support hard links, so each backup will be a full copy instead
+of only storing files that changed since the previous one. File ownership and permissions are
+not preserved either.
+.RE
 .TP
 .B \-e, \-\-exclude FILE|DIR|PATTERN [FILE|...]]
 Specify files, directories or patterns to exclude from the backup. Matching files and directories
@@ -61,6 +69,10 @@ will not be copied. Multiple elements can be specified, in the same way as for t
 .B \-k, \-\-keep N
 Specify how many old backups (so excluding the current one) will be kept. The default behavior
 is to keep them all (same as N=\-1).
+Old backups are only removed if rsync completes successfully, to avoid deleting them when the
+new backup may be incomplete. rsync return code 24 (source files vanished during the transfer)
+is treated as success, while any other error (including return code 23, partial transfer due to error)
+will prevent old backups from being removed. This does not apply when using \-\-remove\-before\-backup.
 .TP
 .B \-u, \-\-user USERNAME
 Explicitly specify the user running the backup (in case it is needed for home directory expansion).
@@ -86,6 +98,9 @@ if saving bandwith is needed.
 Remove old backups (if necessary) before creating the new backup. Useful to free some space
 before performing the backup.
 Default behavior is to remove old backups after successfully completing the backup.
+Note that if the backup fails after old backups have been removed, only the backups kept
+according to \-\-keep will be left, and the new backup may be incomplete. In particular, with
+\-\-keep 0 there will be no complete backup available until the next successful one.
 .TP
 .B \-\-no\-syslog
 Don't use systemd journal for logging.
@@ -100,7 +115,7 @@ Using \-\-rsync\-options it is possible to manually select which options to use.
 .P
     \-a, \-l, \-p, \-t, \-g, \-o, \-c, \-h, \-D, \-H, \-X, \-s
 .P
-Options \-r and \-v are used in any case. Not that options must be specified without dash (\-), for example:
+Options \-r, \-v, \-\-ignore\-missing\-args and \-\-mkpath are used in any case. Note that options must be specified without dash (\-), for example:
 .P
 .EX
     simple_backup \-\-rsync\-options a l p
@@ -131,6 +146,14 @@ Copy it to the default location ($HOME/.config/simple_backup) and edit it as nee
 It is possible to choose a directory on a remote server as destination for the backup. The files
 are copied by rsync through SSH. Server hostname and username must be specified, either in the
 configuration file, or on the command line (\(aq\-\-ssh\-host\(aq and \(aq\-\-ssh\-user\(aq options).
+.P
+The output directory is a path on the server. A leading \(aq~\(aq and relative paths refer to the
+home directory of the user on the server. On the command line, quote \(aq~\(aq so that the local
+shell doesn\(aqt expand it, for example:
+.P
+.EX
+    simple_backup \-\-ssh\-host server \-\-ssh\-user user \-o \(aq~/backups\(aq
+.EE
 .SS AUTHENTICATION
 For authentication, it is possible to use SSH key or password.
 .P
@@ -165,7 +188,8 @@ for details. For this reason, use SSH key authentication if possible.
 .SH EXIT STATUS
 .TP
 .B 0
-The backup was completed without errors.
+The backup was completed without errors. This includes rsync return code 24 (some source files
+vanished during the transfer), which only logs a warning.
 .TP
 .B 1
 No valid inputs selected for backup.
@@ -177,13 +201,13 @@ Backup failed because output directory for storing the backup does not exist.
 Permission denied to access the output directory.
 .TP
 .B 4
-rsync error (rsync returned a non-zero value).
+rsync error (rsync returned a value other than 0 or 24).
 .TP
 .B 5
 SSH connection failed.
 .TP
 .B 6
-Bad configuration file.
+Bad configuration file or options (for example, only one of SSH host and SSH user specified).
 .SH SEE ALSO
 .BR rsync (1)
 .SH AUTHORS

pyproject.toml

@@ -1,3 +1,48 @@
 [build-system]
-requires = ['setuptools']
+requires = ['setuptools>=77']
 build-backend = 'setuptools.build_meta'
+
+[project]
+name = "simple_backup"
+dynamic = ["version"]
+description = "Simple backup script that uses rsync to copy files"
+readme = "README.md"
+requires-python = ">=3.10"
+license = "GPL-3.0-or-later"
+license-files = ["LICENSE"]
+authors = [
+  { name = "Daniele Fucini", email = "dfucini@gmail.com" }
+]
+maintainers = [
+  { name = "Daniele Fucini", email = "dfucini@gmail.com" }
+]
+classifiers = [
+  "Development Status :: 4 - Beta",
+  "Environment :: Console",
+  "Natural Language :: English",
+  "Operating System :: POSIX :: Linux",
+  "Programming Language :: Python :: 3",
+  "Programming Language :: Python :: 3.10",
+  "Programming Language :: Python :: 3.11",
+  "Programming Language :: Python :: 3.12",
+  "Programming Language :: Python :: 3.13",
+  "Programming Language :: Python :: 3.14",
+  "Topic :: System :: Archiving :: Backup",
+]
+
+[project.optional-dependencies]
+JOURNAL = ["systemd-python"]
+NOTIFICATIONS = ["dbus-python"]
+REMOTE = ["paramiko>=3.2"]
+
+[project.urls]
+Homepage = "https://git.shouldnt.work/fuxino/simple_backup"
+
+[project.scripts]
+simple_backup = "simple_backup.simple_backup:simple_backup"
+
+[tool.setuptools]
+packages = ["simple_backup"]
+
+[tool.setuptools.dynamic]
+version = { attr = "simple_backup.__version__" }

setup.cfg

@@ -1,39 +0,0 @@
-[metadata]
-name = simple_backup
-version = attr: simple_backup.__version__
-description = Simple backup script using rsync
-long_description = file: README.md
-author = Daniele Fucini
-author_email = dfucini@gmail.com
-license = GPL3
-url = https://git.shouldnt.work/fuxino
-classifiers =
-   Development Status :: 4 - Beta
-   Environment :: Console
-   License :: OSI Approved :: GNU General Public License v3 (GPLv3)
-   Natural Language :: English
-   Operating System :: POSIX :: Linux
-   Programming Language :: Python :: 3.10
-   Programming Language :: Python :: 3.11
-   Programming Language :: Python :: 3.12
-   Programming Language :: Python :: 3.13
-   Topic :: System :: Archiving :: Backup
-
-[options]
-packages = simple_backup
-python_requires = >=3.10
-install_requires =
-   python-dotenv
-
-[options.extras_require]
-JOURNAL =
-    systemd-python
-NOTIFICATIONS =
-    dbus-python
-REMOTE =
-    paramiko
-
-[options.entry_points]
-console_scripts =
-   simple_backup = simple_backup.simple_backup:simple_backup
-

simple_backup/__init__.py

@@ -1,3 +1,3 @@
 """Init."""
 
-__version__ = '4.1.6'
+__version__ = '4.3.0'

simple_backup/simple_backup.conf

@@ -4,7 +4,7 @@
 # Files and directories to backup. Multiple items can be separated using a comma (','). It is possible to use wildcards (i.e. '*' to match multiple characters and '~' for the user's home directory).
 inputs=/home/user
 
-# Output directory.
+# Output directory. For remote backups, this is a path on the server ('~' and relative paths refer to the home directory on the server).
 backup_dir=/media/Backup
 
 # Files, directories and patterns to exclude from the backup. Multiple items can be separated using a comma.
@@ -18,5 +18,5 @@ keep=-1
 # ssh_host=
 # ssh_user=
 # ssh_keyfile=
-# remote_sudo=
-# numeric_ids=
+# remote_sudo=false
+# numeric_ids=false

simple_backup/simple_backup.py

@@ -11,8 +11,10 @@ Classes:
     Backup
 """
 
+# Avoid evaluating annotations at definition time, as they reference optional modules (paramiko)
+from __future__ import annotations
+
 # Import libraries
-import traceback
 import sys
 import os
 import pwd
@@ -32,13 +34,8 @@ from tempfile import mkstemp
 from getpass import GetPassWarning, getpass
 from glob import glob
 
-from dotenv import load_dotenv
-
-warnings.filterwarnings('error')
-
 try:
     import paramiko
-    from paramiko import RSAKey, Ed25519Key, ECDSAKey, DSSKey
 except ImportError:
     pass
 
@@ -50,10 +47,9 @@ except ImportError:
 try:
     import dbus
 except ImportError:
-    pass
+    dbus = None
 
 
-load_dotenv()
 logging.getLogger().setLevel(logging.DEBUG)
 logger = logging.getLogger(os.path.basename(__file__))
 c_handler = StreamHandler()
@@ -73,6 +69,9 @@ if journal:
 P = ParamSpec('P')
 R = TypeVar('R')
 
+# Seconds to wait for the TCP connection to the SSH server
+SSH_TIMEOUT = 15
+
 
 def timing(func: Callable[P, R]) -> Callable[P, R]:
     """Decorator to measure execution time of a function
@@ -159,7 +158,7 @@ class Backup:
         self._remote = False
         self._ssh = None
         self._password_auth = False
-        self._password = None
+        self._removed_count = 0
 
     def check_params(self, homedir: str = '') -> int:
         """Check if parameters for the backup are valid"""
@@ -180,37 +179,66 @@ class Backup:
             self._remote = True
 
         if self._remote:
-            self._ssh = self._ssh_connect(homedir)
+            try:
+                self._ssh = self._ssh_connect(homedir)
+            except OSError as e:
+                # Unknown hostname, connection refused, unreachable host or timeout
+                logger.critical('Can\'t connect to the server %s', self.ssh_host)
+                logger.critical(e)
+
+                return 5
 
             if self._ssh is None:
                 return 5
 
-            _, stdout, _ = self._ssh.exec_command(
-                f'if [ -d "{self.output}" ]; then echo "ok"; fi')
+            output = self._resolve_remote_path(self.output)
 
-            output = stdout.read().decode('utf-8').strip()
-
-            if output != 'ok':
+            if output is None:
                 logger.critical('Output path for backup does not exist')
 
                 return 2
+
+            self.output = output
         else:
             if not os.path.isdir(self.output):
                 logger.critical('Output path for backup does not exist')
 
                 return 2
 
-        self.output = os.path.abspath(self.output)
+            self.output = os.path.abspath(self.output)
 
         if self.keep is None:
             self.keep = -1
 
         return 0
 
+    def _resolve_remote_path(self, path: str) -> Optional[str]:
+        """Return the absolute path of a directory on the server, or None if it doesn't exist"""
+
+        assert self._ssh is not None
+
+        # Leave a leading '~' unquoted, so that the server's shell expands it to the remote home.
+        # Relative paths are resolved from the remote home, where the command starts
+        if path == '~' or path.startswith('~/'):
+            target = f'~/{shlex.quote(path[2:])}'
+        else:
+            target = shlex.quote(path)
+
+        _, stdout, _ = self._ssh.exec_command(f'cd -- {target} && pwd')
+
+        output = stdout.read().decode('utf-8').strip().split('\n')[-1]
+
+        if not output.startswith('/'):
+            return None
+
+        return output
+
     # Function to create the actual backup directory
     def define_backup_dir(self) -> None:
         """Define the actual backup dir"""
-        now = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
+        # Avoid ':', which is not allowed on FAT/exFAT filesystems.
+        # Backups created with the old format ('%Y-%m-%d %H:%M:%S') still sort correctly
+        now = datetime.now().strftime('%Y-%m-%d_%H-%M-%S')
         self._output_dir = f'{self.output}/simple_backup/{now}'
 
         if self._remote:
@@ -222,10 +250,23 @@ class Backup:
         if self._remote:
             assert self._ssh is not None
 
-            _, stdout, _ = self._ssh.exec_command(
-                f'ls {self.output}/simple_backup')
+            backup_dir = shlex.quote(self.output + '/simple_backup/')
 
-            dirs = stdout.read().decode('utf-8').strip().split('\n')
+            # List only directories, and nothing (without errors) if no backup was made yet
+            _, stdout, stderr = self._ssh.exec_command(
+                f'if [ -d {backup_dir} ]; then find {backup_dir} -mindepth 1 -maxdepth 1 -type d; fi')
+
+            output = stdout.read().decode('utf-8')
+            err = stderr.read().decode('utf-8').strip()
+
+            if err != '':
+                # Don't risk removing the wrong directories if the list may be incomplete
+                logger.error('Cannot list old backups on the server. Old backups will not be removed')
+                logger.error(err)
+
+                return
+
+            dirs = [os.path.basename(d) for d in output.split('\n') if d != '']
 
             n_backup = len(dirs)
 
@@ -241,24 +282,30 @@ class Backup:
                 for i in range(n_backup - self.keep):
                     if self.remote_sudo:
                         _, _, stderr = self._ssh.exec_command(
-                            f'sudo rm -r "{self.output}/simple_backup/{dirs[i]}"')
+                            f'sudo rm -r {shlex.quote(f"{self.output}/simple_backup/{dirs[i]}")}')
                     else:
                         _, _, stderr = self._ssh.exec_command(
-                            f'rm -r "{self.output}/simple_backup/{dirs[i]}"')
+                            f'rm -r {shlex.quote(f"{self.output}/simple_backup/{dirs[i]}")}')
 
                     err = stderr.read().decode('utf-8').strip().split('\n')[0]
 
                     if err != '':
                         logger.error(
-                            'Error while removing backup %s.', {dirs[i]})
+                            'Error while removing backup %s.', dirs[i])
                         logger.error(err)
                     else:
                         count += 1
         else:
             try:
-                dirs = os.listdir(f'{self.output}/simple_backup')
+                # Only count directories, so that stray files don't count as backups
+                dirs = [f.name for f in os.scandir(f'{self.output}/simple_backup')
+                        if f.is_dir(follow_symlinks=False)]
             except FileNotFoundError:
                 return
+            except PermissionError:
+                logger.error('Cannot list old backups. Permission denied. Old backups will not be removed')
+
+                return
 
             n_backup = len(dirs)
 
@@ -282,6 +329,8 @@ class Backup:
                         logger.error(
                             'Error while removing backup %s. Permission denied', dirs[i])
 
+        self._removed_count = count
+
         if count == 1:
             logger.info('Removed %d backup', count)
         elif count > 1:
@@ -296,7 +345,7 @@ class Backup:
                 sys.exit(5)
 
             _, stdout, _ = self._ssh.exec_command(
-                f'find {self.output}/simple_backup/ -mindepth 1 -maxdepth 1 -type d | sort')
+                f'find {shlex.quote(self.output + "/simple_backup/")} -mindepth 1 -maxdepth 1 -type d | sort')
             output = stdout.read().decode('utf-8').strip().split('\n')
 
             if output[-1] != '':
@@ -315,10 +364,7 @@ class Backup:
                 logger.critical(
                     'Cannot access the backup directory. Permission denied')
 
-                try:
-                    _notify('Backup failed (check log for details)')
-                except NameError:
-                    pass
+                _notify('Backup failed (check log for details)')
 
                 sys.exit(3)
 
@@ -327,7 +373,7 @@ class Backup:
             except IndexError:
                 logger.info('No previous backups available')
 
-    def _ssh_connect(self, homedir: str = '') -> paramiko.client.SSHClient:
+    def _ssh_connect(self, homedir: str = '') -> Optional[paramiko.client.SSHClient]:
         try:
             ssh = paramiko.SSHClient()
         except NameError:
@@ -335,6 +381,18 @@ class Backup:
 
             return None
 
+        connected = None
+
+        try:
+            connected = self._ssh_login(ssh, homedir)
+
+            return connected
+        finally:
+            # Don't leave a half-open connection (e.g. after failed authentication)
+            if connected is None:
+                ssh.close()
+
+    def _ssh_login(self, ssh: paramiko.client.SSHClient, homedir: str) -> Optional[paramiko.client.SSHClient]:
         try:
             ssh.load_host_keys(filename=f'{homedir}/.ssh/known_hosts')
         except FileNotFoundError:
@@ -343,16 +401,25 @@ class Backup:
         ssh.set_missing_host_key_policy(paramiko.WarningPolicy())
 
         try:
-            ssh.connect(self.ssh_host, username=self.ssh_user)
+            # WarningPolicy emits a UserWarning for unknown host keys
+            with warnings.catch_warnings():
+                warnings.simplefilter('error', UserWarning)
+                ssh.connect(self.ssh_host, username=self.ssh_user, timeout=SSH_TIMEOUT)
 
             return ssh
         except UserWarning:
-            k = input(
-                f'Unknown key for host {self.ssh_host}. Continue anyway? (Y/N) ')
+            try:
+                k = input(
+                    f'Unknown key for host {self.ssh_host}. Continue anyway? (Y/N) ')
+            except EOFError:
+                # No terminal available (e.g. cron or systemd)
+                k = ''
 
-            if k[0].upper() == 'Y':
+            if k.strip().upper().startswith('Y'):
                 ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
             else:
+                logger.critical('Unknown host key for %s. Connection aborted', self.ssh_host)
+
                 return None
         except paramiko.BadHostKeyException as e:
             logger.critical('Can\'t connect to the server.')
@@ -363,7 +430,7 @@ class Backup:
             pass
 
         try:
-            ssh.connect(self.ssh_host, username=self.ssh_user)
+            ssh.connect(self.ssh_host, username=self.ssh_user, timeout=SSH_TIMEOUT)
 
             return ssh
         except paramiko.SSHException:
@@ -371,9 +438,13 @@ class Backup:
 
         if self.ssh_keyfile is None:
             try:
-                password = getpass(
-                    f'{self.ssh_user}@{self.ssh_host}\'s password: ')
-                ssh.connect(self.ssh_host, username=self.ssh_user,
+                # Fail instead of reading the password with echo if no terminal is available
+                with warnings.catch_warnings():
+                    warnings.simplefilter('error', GetPassWarning)
+                    password = getpass(
+                        f'{self.ssh_user}@{self.ssh_host}\'s password: ')
+
+                ssh.connect(self.ssh_host, username=self.ssh_user, timeout=SSH_TIMEOUT,
                             password=password)
 
                 self._password_auth = True
@@ -391,51 +462,13 @@ class Backup:
 
                 return None
 
-        pkey = None
+        pkey = self._load_ssh_key()
+
+        if pkey is None:
+            return None
 
         try:
-            pkey = RSAKey.from_private_key_file(self.ssh_keyfile)
-        except paramiko.PasswordRequiredException:
-            password = getpass(
-                f'Enter passwphrase for key \'{self.ssh_keyfile}\': ')
-
-            try:
-                pkey = RSAKey.from_private_key_file(self.ssh_keyfile, password)
-            except paramiko.SSHException:
-                pass
-
-        if pkey is None:
-            try:
-                pkey = Ed25519Key.from_private_key_file(self.ssh_keyfile)
-            except paramiko.PasswordRequiredException:
-                try:
-                    pkey = Ed25519Key.from_private_key_file(
-                        self.ssh_keyfile, password)
-                except paramiko.SSHException:
-                    pass
-
-        if pkey is None:
-            try:
-                pkey = ECDSAKey.from_private_key_file(self.ssh_keyfile)
-            except paramiko.PasswordRequiredException:
-                try:
-                    pkey = ECDSAKey.from_private_key_file(
-                        self.ssh_keyfile, password)
-                except paramiko.SSHException:
-                    pass
-
-        if pkey is None:
-            try:
-                pkey = DSSKey.from_private_key_file(self.ssh_keyfile)
-            except paramiko.PasswordRequiredException:
-                try:
-                    pkey = DSSKey.from_private_key_file(
-                        self.ssh_keyfile, password)
-                except paramiko.SSHException:
-                    pass
-
-        try:
-            ssh.connect(self.ssh_host, username=self.ssh_user, pkey=pkey)
+            ssh.connect(self.ssh_host, username=self.ssh_user, timeout=SSH_TIMEOUT, pkey=pkey)
         except paramiko.SSHException:
             logger.critical('SSH connection to server failed')
 
@@ -443,6 +476,37 @@ class Backup:
 
         return ssh
 
+    def _load_ssh_key(self) -> Optional[paramiko.PKey]:
+        try:
+            return paramiko.PKey.from_path(self.ssh_keyfile)
+        except TypeError:
+            # Raised when the key is encrypted and no passphrase was given
+            pass
+        except (OSError, ValueError, paramiko.UnknownKeyType) as e:
+            logger.critical('Unable to load SSH key %s', self.ssh_keyfile)
+            logger.critical(e)
+
+            return None
+
+        try:
+            # Fail instead of reading the passphrase with echo if no terminal is available
+            with warnings.catch_warnings():
+                warnings.simplefilter('error', GetPassWarning)
+                passphrase = getpass(
+                    f'Enter passphrase for key \'{self.ssh_keyfile}\': ')
+        except GetPassWarning as e:
+            logger.critical('Unable to get passphrase')
+            logger.critical(e)
+
+            return None
+
+        try:
+            return paramiko.PKey.from_path(self.ssh_keyfile, passphrase.encode())
+        except (ValueError, paramiko.SSHException):
+            logger.critical('Unable to load SSH key %s, wrong passphrase?', self.ssh_keyfile)
+
+            return None
+
     def _returncode_log(self, returncode: int) -> None:
         match returncode:
             case 2:
@@ -474,7 +538,7 @@ class Backup:
                     'Rsync error (return code 23) - Partial transfer due to error')
             case 24:
                 logger.warning(
-                    'Rsync error (return code 24) - Partial transfer due to vanished source files')
+                    'Rsync warning (return code 24) - Some source files vanished during the transfer')
             case 30:
                 logger.error(
                     'Rsync error (return code 30) - Timeout in data send/receive')
@@ -490,25 +554,43 @@ class Backup:
     def run(self) -> int:
         """Perform the backup"""
 
+        try:
+            return self._run()
+        finally:
+            self._remove_temp_files()
+
+    def close(self) -> None:
+        """Close the SSH connection, if open"""
+
+        if self._ssh is not None:
+            self._ssh.close()
+            self._ssh = None
+
+    def _remove_temp_files(self) -> None:
+        for path in [self._inputs_path, self._exclude_path]:
+            if path != '':
+                try:
+                    os.remove(path)
+                except FileNotFoundError:
+                    pass
+
+    def _run(self) -> int:
         logger.info('Starting backup...')
 
-        try:
-            _notify('Starting backup...')
-        except NameError:
-            pass
+        _notify('Starting backup...')
 
         self.define_backup_dir()
-        self.find_last_backup()
 
-        _, self._inputs_path = mkstemp(prefix='tmp_inputs', text=True)
+        fd, self._inputs_path = mkstemp(prefix='tmp_inputs', text=True)
         count = 0
 
-        with open(self._inputs_path, 'w', encoding='utf-8') as fp:
+        with os.fdopen(fd, 'w', encoding='utf-8') as fp:
             for i in self.inputs:
                 if not os.path.exists(i):
                     logger.warning('Input %s not found. Skipping', i)
                 else:
-                    fp.write(i)
+                    # rsync reads --files-from paths relative to the source ('/')
+                    fp.write(os.path.abspath(i))
                     fp.write('\n')
                     count += 1
 
@@ -516,16 +598,13 @@ class Backup:
             logger.info(
                 'No existing files or directories specified for backup. Nothing to do')
 
-            try:
-                _notify('Backup finished. No files copied')
-            except NameError:
-                pass
+            _notify('Backup finished. No files copied')
 
             return 1
 
-        _, self._exclude_path = mkstemp(prefix='tmp_exclude', text=True)
+        fd, self._exclude_path = mkstemp(prefix='tmp_exclude', text=True)
 
-        with open(self._exclude_path, 'w', encoding='utf-8') as fp:
+        with os.fdopen(fd, 'w', encoding='utf-8') as fp:
             if self.exclude is not None:
                 for e in self.exclude:
                     fp.write(e)
@@ -534,28 +613,32 @@ class Backup:
         if self.keep != -1 and self._remove_before:
             self.remove_old_backups()
 
+        # Only look for the last backup now, as it may have been removed above
+        self.find_last_backup()
+
         logger.info('Copying files. This may take a long time...')
 
-        if self._last_backup == '':
-            rsync = f'/usr/bin/rsync {self.options} --exclude-from={self._exclude_path} ' +\
-                f'--files-from={self._inputs_path} / "{self._server}{self._output_dir}"'
-        else:
-            rsync = f'/usr/bin/rsync {self.options} --link-dest="{self._last_backup}" --exclude-from=' +\
-                f'{self._exclude_path} --files-from={self._inputs_path} / "{self._server}{self._output_dir}"'
+        # Build the argument list directly, so paths with spaces or quotes are passed unchanged
+        args = ['/usr/bin/rsync', *self.options.split()]
 
-        euid = os.geteuid()
+        if self._last_backup != '':
+            args.append(f'--link-dest={self._last_backup}')
 
-        if euid == 0 and self.ssh_keyfile is not None:
-            rsync = f'{rsync} -e \'ssh -i {self.ssh_keyfile} -o StrictHostKeyChecking=no\''
+        args.extend([f'--exclude-from={self._exclude_path}', f'--files-from={self._inputs_path}',
+                     '/', f'{self._server}{self._output_dir}'])
+
+        # rsync splits the -e command itself, so quote the parts that may contain spaces
+        if self.ssh_keyfile is not None:
+            ssh = f'ssh -i {shlex.quote(self.ssh_keyfile)} -o StrictHostKeyChecking=accept-new'
         elif self._password_auth and which('sshpass'):
-            rsync = f'{rsync} -e \'sshpass -e ssh -l {self.ssh_user} -o StrictHostKeyChecking=no\''
+            ssh = f'sshpass -e ssh -l {shlex.quote(self.ssh_user)} -o StrictHostKeyChecking=accept-new'
         else:
-            rsync = f'{rsync} -e \'ssh -o StrictHostKeyChecking=no\''
+            ssh = 'ssh -o StrictHostKeyChecking=accept-new'
+
+        args.extend(['-e', ssh])
 
         if self._remote and self.remote_sudo:
-            rsync = f'{rsync} --rsync-path="sudo rsync"'
-
-        args = shlex.split(rsync)
+            args.append('--rsync-path=sudo rsync')
 
         with Popen(args, stdin=PIPE, stdout=PIPE, stderr=STDOUT, shell=False) as p:
             output: Union[bytes, List[str]]
@@ -585,70 +668,49 @@ class Backup:
                 else:
                     logger.error(output)
 
-        if self.keep != -1 and not self._remove_before:
-            self.remove_old_backups()
-
-        os.remove(self._inputs_path)
-        os.remove(self._exclude_path)
-
-        if self._remote:
-            assert self._ssh is not None
-
-            _, stdout, _ = self._ssh.exec_command(
-                f'if [ -d "{self._output_dir}" ]; then echo "ok"; fi')
-
-            output = stdout.read().decode('utf-8').strip()
-
-            if output == 'ok':
-                logger.info('Backup completed')
-
-                try:
-                    _notify('Backup completed')
-                except NameError:
-                    pass
+        if self._removed_count > 0 and returncode not in [0, 24]:
+            # With --remove-before-backup, old backups are already gone if the new one failed
+            if self.keep == 0:
+                message = 'All old backups were removed before the backup, and the new backup may be ' +\
+                    'incomplete. No complete backup is available'
             else:
-                logger.error('Backup failed')
+                message = 'Old backups were removed before the backup, and the new backup may be incomplete'
 
-                try:
-                    _notify('Backup failed (check log for details)')
-                except NameError:
-                    pass
+            logger.error(message)
+            _notify(message)
 
-            if self._ssh:
-                self._ssh.close()
-        else:
-            if returncode != 0:
-                logger.error(
-                    'Some errors occurred while performing the backup')
+        if self.keep != -1 and not self._remove_before:
+            # Don't delete old backups if the new one may be incomplete
+            if returncode in [0, 24]:
+                self.remove_old_backups()
+            else:
+                logger.warning('Backup not completed successfully. Old backups will not be removed')
 
-                try:
-                    _notify(
-                        'Some errors occurred while performing the backup. Check log for details')
-                except NameError:
-                    pass
+        # Files vanishing during the transfer is normal for a live system (return code 24)
+        if returncode not in [0, 24]:
+            logger.error(
+                'Some errors occurred while performing the backup')
 
-                return 4
+            _notify(
+                'Some errors occurred while performing the backup. Check log for details')
 
-            logger.info('Backup completed')
+            return 4
 
-            try:
-                _notify('Backup completed')
-            except NameError:
-                pass
+        logger.info('Backup completed')
 
-            return 0
+        _notify('Backup completed')
+
+        return 0
+
+
+def _detect_user() -> Optional[str]:
+    if os.geteuid() == 0:
+        return os.getenv('SUDO_USER') or os.getenv('DOAS_USER')
+
+    return os.getenv('USER')
 
 
 def _parse_arguments() -> argparse.Namespace:
-    euid = os.geteuid()
-
-    if euid == 0:
-        user = os.getenv('SUDO_USER')
-    else:
-        user = os.getenv('USER')
-
-    homedir = os.path.expanduser(f'~{user}')
-
     parser = argparse.ArgumentParser(prog='simple_backup',
                                      description='Simple backup script written in Python that uses rsync to copy files',
                                      epilog='See simple_backup(1) manpage for full documentation',
@@ -656,7 +718,7 @@ def _parse_arguments() -> argparse.Namespace:
 
     parser.add_argument('-v', '--verbose', action='store_true',
                         help='More verbose output')
-    parser.add_argument('-c', '--config', default=f'{homedir}/.config/simple_backup/simple_backup.conf',
+    parser.add_argument('-c', '--config', default='~/.config/simple_backup/simple_backup.conf',
                         help='Specify location of configuration file')
     parser.add_argument('-i', '--inputs', nargs='+',
                         help='Paths/files to backup')
@@ -695,6 +757,15 @@ def _parse_arguments() -> argparse.Namespace:
     return args
 
 
+def _expand_home(path: str, user: str) -> str:
+    """Expand a leading '~' to the home directory of user (other '~' are left as they are)"""
+
+    if path == '~' or path.startswith('~/'):
+        path = f'~{user}{path[1:]}'
+
+    return os.path.expanduser(path)
+
+
 def _expand_inputs(inputs, user: Optional[str] = None):
     expanded_inputs = []
 
@@ -703,11 +774,11 @@ def _expand_inputs(inputs, user: Optional[str] = None):
             continue
 
         if user is not None:
-            i_ex = glob(os.path.expanduser(i.replace('~', f'~{user}')))
+            i_ex = glob(_expand_home(i, user))
         else:
             i_ex = glob(i)
 
-            if '~' in i:
+            if i.startswith('~'):
                 logger.warning('Cannot expand \'~\'. No user specified')
 
         if len(i_ex) == 0:
@@ -739,7 +810,8 @@ def _read_config(config_file, user: Optional[str] = None):
 
         return config_args
 
-    config = configparser.ConfigParser()
+    # Disable interpolation, so that '%' can be used in paths and patterns
+    config = configparser.ConfigParser(interpolation=None)
     config.read(config_file)
 
     section = 'backup'
@@ -751,24 +823,18 @@ def _read_config(config_file, user: Optional[str] = None):
         section = 'default'
         inputs = config.get(section, 'inputs')
 
-    inputs = inputs.split(',')
+    inputs = [i.strip() for i in inputs.split(',')]
     inputs = _expand_inputs(inputs, user)
     inputs = list(set(inputs))
 
     config_args['inputs'] = inputs
 
-    output = config.get(section, 'backup_dir')
-
-    if user is not None:
-        output = os.path.expanduser(output.replace('~', f'~{user}'))
-    elif user is None and '~' in output:
-        logger.warning('Cannot expand \'~\', no user specified')
-
-    config_args['output'] = output
+    # '~' is expanded later, since for remote backups it refers to the home on the server
+    config_args['output'] = config.get(section, 'backup_dir')
 
     try:
         exclude = config.get(section, 'exclude')
-        exclude = exclude.split(',')
+        exclude = [e.strip() for e in exclude.split(',') if e.strip() != '']
     except configparser.NoOptionError:
         exclude = []
 
@@ -781,36 +847,19 @@ def _read_config(config_file, user: Optional[str] = None):
 
     config_args['keep'] = keep
 
-    try:
-        ssh_host = config.get('server', 'ssh_host')
-        ssh_user = config.get('server', 'ssh_user')
-    except (configparser.NoSectionError, configparser.NoOptionError):
-        ssh_host = None
-        ssh_user = None
+    # Read host and user separately, so that a missing one is reported instead of silently
+    # disabling remote backup. Empty values count as not set
+    config_args['ssh_host'] = config.get('server', 'ssh_host', fallback='').strip() or None
+    config_args['ssh_user'] = config.get('server', 'ssh_user', fallback='').strip() or None
 
-    config_args['ssh_host'] = ssh_host
-    config_args['ssh_user'] = ssh_user
+    config_args['ssh_keyfile'] = config.get('server', 'ssh_keyfile', fallback='').strip() or None
 
-    try:
-        ssh_keyfile = config.get('server', 'ssh_keyfile')
-    except (configparser.NoSectionError, configparser.NoOptionError):
-        ssh_keyfile = None
-
-    config_args['ssh_keyfile'] = ssh_keyfile
-
-    try:
-        remote_sudo = config.getboolean('server', 'remote_sudo')
-    except (configparser.NoSectionError, configparser.NoOptionError):
-        remote_sudo = False
-
-    config_args['remote_sudo'] = remote_sudo
-
-    try:
-        numeric_ids = config.getboolean('server', 'numeric_ids')
-    except (configparser.NoSectionError, configparser.NoOptionError):
-        numeric_ids = False
-
-    config_args['numeric_ids'] = numeric_ids
+    # Empty values (as in the example config) count as false
+    for key in ['remote_sudo', 'numeric_ids']:
+        if config.get('server', key, fallback='').strip() == '':
+            config_args[key] = False
+        else:
+            config_args[key] = config.getboolean('server', key)
 
     return config_args
 
@@ -833,12 +882,20 @@ def _target_uid() -> int | None:
     return None
 
 
+_notify_failed = False
+
+
 def _notify(text: str) -> None:
+    global _notify_failed
+
+    if dbus is None or _notify_failed:
+        return
+
     euid = os.geteuid()
     uid = _target_uid()
 
     if uid is None:
-        print('notify: no target uid (neither SUDO_UID nor DOAS_USER set)', file=sys.stderr)
+        logger.debug('Cannot send desktop notification: user not found')
 
         return
 
@@ -851,8 +908,10 @@ def _notify(text: str) -> None:
                                            '/org/freedesktop/Notifications')
         obj = dbus.Interface(obj, 'org.freedesktop.Notifications')
         obj.Notify('simple_backup', 0, '', 'simple_backup', text, [], {'urgency': dbus.Byte(1)}, 10000)
-    except Exception:
-        traceback.print_exc()
+    except Exception as e:
+        # Report the failure only once (e.g. no session bus available), then stop trying
+        _notify_failed = True
+        logger.warning('Cannot send desktop notification: %s', e)
     finally:
         os.seteuid(euid)
 
@@ -869,7 +928,7 @@ def simple_backup() -> int:
         euid = os.geteuid()
 
         if euid == 0:
-            user = os.getenv('SUDO_USER')
+            user = _detect_user()
 
             if user is not None:
                 homedir = os.path.expanduser(f'~{user}')
@@ -890,28 +949,56 @@ def simple_backup() -> int:
         except NameError:
             pass
 
+    config_file = args.config
+
+    # Expand '~' to the home of the user running the backup, not root's
+    if config_file.startswith('~/') and user is not None:
+        config_file = f'~{user}{config_file[1:]}'
+
+    config_file = os.path.expanduser(config_file)
+
     try:
-        config_args = _read_config(args.config, user)
-    except (configparser.NoSectionError, configparser.NoOptionError):
-        logger.critical('Bad configuration file')
+        config_args = _read_config(config_file, user)
+    except (configparser.Error, ValueError) as e:
+        # configparser.Error: missing sections/options or bad syntax, ValueError: invalid values (e.g. keep=abc)
+        logger.critical('Bad configuration file: %s', e)
 
         return 6
 
     inputs = args.inputs if args.inputs is not None else config_args['inputs']
-    output = args.output if args.output is not None else config_args['output']
     exclude = args.exclude if args.exclude is not None else config_args['exclude']
     keep = args.keep if args.keep is not None else config_args['keep']
     ssh_host = args.ssh_host if args.ssh_host is not None else config_args['ssh_host']
     ssh_user = args.ssh_user if args.ssh_user is not None else config_args['ssh_user']
+
+    if (ssh_host is None) != (ssh_user is None):
+        logger.critical('Both SSH host and SSH user are needed for remote backup')
+
+        return 6
+
+    if args.output is not None:
+        output = args.output
+    else:
+        output = config_args['output']
+
+        # For remote backups, '~' is expanded on the server
+        remote = ssh_host is not None and ssh_user is not None
+
+        if output is not None and not remote:
+            if user is not None:
+                output = _expand_home(output, user)
+            elif output.startswith('~'):
+                logger.warning('Cannot expand \'~\', no user specified')
+
     ssh_keyfile = args.keyfile if args.keyfile is not None else config_args['ssh_keyfile']
     remote_sudo = args.remote_sudo or config_args['remote_sudo']
 
-    if args.rsync_options is None:
-        rsync_options = ['-a', '-r', '-v', '-h', '-H',
-                         '-X', '-s', '--ignore-missing-args', '--mkpath']
-    else:
-        rsync_options = ['-r', '-v']
+    # Options needed in any case (--mkpath creates the backup directory on the first run)
+    rsync_options = ['-r', '-v', '--ignore-missing-args', '--mkpath']
 
+    if args.rsync_options is None:
+        rsync_options.extend(['-a', '-h', '-H', '-X', '-s'])
+    else:
         for ro in args.rsync_options:
             rsync_options.append(f'-{ro}')
 
@@ -929,12 +1016,15 @@ def simple_backup() -> int:
     backup = Backup(inputs, output, exclude, keep, rsync_options, ssh_host, ssh_user, ssh_keyfile,
                     remote_sudo, remove_before=args.remove_before_backup, verbose=args.verbose)
 
-    return_code = backup.check_params(homedir)
+    try:
+        return_code = backup.check_params(homedir)
 
-    if return_code == 0:
-        return backup.run()
+        if return_code == 0:
+            return backup.run()
 
-    return return_code
+        return return_code
+    finally:
+        backup.close()
 
 
 if __name__ == '__main__':