auto-reboot

Conditional system reboot scheduler with flexible timing and day-of-week restrictions.

Version: 1.4.1 License: GPL-3.0

Overview

auto-reboot schedules a system reboot via a systemd transient timer when any of these holds:

• System updates require a reboot (/var/run/reboot-required exists)
• Uptime has reached the maximum threshold (default: 14 days)
• A reboot is forced with -f

Dry-run by default. Requires explicit -N to execute.

Site defaults live in /etc/auto-reboot.conf; command-line options override them.

Only one reboot is pending at a time. When an auto-reboot timer already exists, a new run reports it and schedules nothing, so a nightly cron entry never stacks timers.

Requirements

• Linux with systemd (systemd-run and systemctl, both in the systemd package)
• Bash 5.2+
• update-notifier-common: its notify-reboot-required hook is what writes /var/run/reboot-required after kernel or library updates. Without it only the uptime threshold can trigger a reboot. make install installs the package when the hook is missing.
• Root, or membership of the sudo group, to execute (-N), delete timers, or install. Dry runs and --list work for any user.

When invoked by a sudo group member, the script re-executes itself through sudo and forwards its settings as options.

Quick Start

# Check whether a reboot is needed (dry run, no root required)
auto-reboot

# Schedule the reboot if conditions are met
auto-reboot -N

# Force a reboot at 03:00
auto-reboot -f -r 03:00 -N

# List scheduled reboots
auto-reboot -l

# Preview, then delete all scheduled reboots
auto-reboot -D
auto-reboot -N -D

Installation

sudo make install      # script (root-owned 0755), manpage, bash completion, /etc/auto-reboot.conf
sudo make check        # verify the install, including the config and the reboot-required hook
sudo make uninstall    # keeps /etc/auto-reboot.conf if it was edited

/etc/auto-reboot.conf is installed once, with default values, and never overwritten. make install also runs apt-get install update-notifier-common when /usr/share/update-notifier/notify-reboot-required is absent. Set DESTDIR for a staged install; the package step is skipped.

auto-reboot --install copies only the script, root-owned, to $PREFIX/bin (default /usr/local).

Root's cron runs this script. Never install it group-writable or as a symlink into a user's checkout.

Options

Option	Description
-n, --dry-run	Test mode, no execution (default)
-N, --not-dry-run	Execute for real
-f, --force-reboot	Force reboot regardless of conditions
-v, --verbose	Verbose output (default)
-q, --quiet	Suppress informational messages
-m, --max-uptime-days DAYS	Max uptime before reboot (default: 14)
-r, --reboot-time HH:MM	Scheduled reboot time (default: 22:00)
-a, --allowed-days DAYS	Restrict to specific days (see below)
-l, --list	List all scheduled reboots
-d, --delete TIMER	Delete one timer immediately (ID or full name)
-D, --delete-all	Dry run lists what would be deleted; -N -D confirms, then deletes
-i, --install	Install a root-owned copy to $PREFIX/bin
-V, --version	Show version
-h, --help	Show help

Short options can be bundled: -Nf is equivalent to -N -f. Standalone operations (-l, -d, -D, -i, -V, -h) run as soon as they are parsed, so -N must come before -D.

Day Specifications

The --allowed-days option accepts comma-separated values in any of these formats:

Format	Example
Short names	Sun, Mon, Tue, Wed, Thu, Fri, Sat
Full names	Sunday, Monday, ..., Saturday
Numbers	0 (Sunday) through 6 (Saturday)
Mixed	Mon,Wed,5

Case insensitive. Whitespace around commas is ignored.

Configuration File

/etc/auto-reboot.conf holds the site defaults. It is sourced as bash, so it must be owned by root, must not be group- or world-writable, and should contain only these assignments:

Key	Default	Description	Overridden by
MACHINE_REBOOT_TIME	22:00	Reboot time (HH:MM, 00:00 to 23:59)	--reboot-time
MACHINE_UPTIME_MAXDAYS	14	Max uptime in days (positive integer)	--max-uptime-days
MACHINE_ALLOWED_DAYS	empty (any day)	Day list, same formats as --allowed-days	--allowed-days ('' clears)

Values are validated at startup (exit 19 on a bad value or a file that fails to load, 13 on a file root cannot trust). No other path is searched, and there is no per-user config: the script runs as root. A typical fleet file:

MACHINE_REBOOT_TIME=04:20
MACHINE_UPTIME_MAXDAYS=14
MACHINE_ALLOWED_DAYS=Sun

The only environment variable is PREFIX (default /usr/local), the installation prefix for --install.

Scheduling Logic

1. No day restrictions: today at the given time, or tomorrow if that time has passed.
2. With day restrictions: the next allowed day within 7 days.
3. Force reboot: bypasses the reboot-required and uptime checks; time and day restrictions still apply.
4. One pending reboot: an existing auto-reboot-*.timer is reported and left alone.

Timers are transient systemd units named auto-reboot-EPOCH.timer, created with systemd-run --on-calendar and AccuracySec=1s. The target is an absolute wall-clock timestamp, so a clock adjustment between scheduling and firing cannot move the reboot off its intended slot.

Exit Status

Code	Meaning
0	Success
1	Runtime failure (systemd not running, scheduling failed, cannot prompt)
2	Unexpected positional argument
13	Not root and not in the sudo group; or config file not root-owned or writable by others
18	systemd-run not found
19	Config file failed to load, or holds an invalid value
22	Invalid option or option value

Examples

Cron Integration

# Nightly check using the settings in /etc/auto-reboot.conf
15 23 * * * /usr/local/bin/auto-reboot -q -N

# Same, overriding the file: reboot Sunday 04:00 once uptime reaches 14 days
0 23 * * * /usr/local/bin/auto-reboot -q -m 14 -r 04:00 -a Sun -N

# Check every 6 hours, reboot at 22:00 once uptime reaches 30 days
0 */6 * * * /usr/local/bin/auto-reboot -q -m 30 -N

# Weekly forced reboot Sunday at 03:00
0 2 * * 0 /usr/local/bin/auto-reboot -qf -r 03:00 -N

Use -q under cron: only errors reach the mail spool.

Schedule Management

# List active timers (no root needed)
auto-reboot --list

# Delete one timer by timestamp ID
auto-reboot --delete 1753063354

# Preview a delete-all, then run it with confirmation
auto-reboot -D
auto-reboot -N -D

Logging

Schedule and delete operations are logged to syslog via logger -t auto-reboot:

sudo journalctl -t auto-reboot

Safety Features

• Dry run by default, for scheduling and for --delete-all
• Lazy privilege elevation: only -N, delete, and install go through sudo
• Trusted config only: /etc/auto-reboot.conf is refused unless root-owned and not writable by others
• Confirmation prompt before -N -D deletes anything; refuses without a terminal
• Input validation of times, day lists, integers, and config values before anything runs
• One pending reboot per host
• Readonly state frozen after argument parsing
• Syslog audit trail with the invoking user's name

Testing

./run_tests.sh              # full BATS suite
./run_tests.sh cli          # one suite
make test                   # suite plus shellcheck

The suite pins the clock (one epoch, UTC) and mocks uptime, systemctl, systemd-run, logger, sudo, id, install, stat, and apt-get; it never touches the real system.

Troubleshooting

# Verify systemd-run is available
command -v systemd-run

# Check systemd health (degraded is tolerated, offline is not)
systemctl is-system-running

# Inspect timers directly
systemctl list-timers --all | grep auto-reboot

# Recent log lines
journalctl -t auto-reboot --since "1 hour ago"

File Structure

auto-reboot                  # Main script
auto-reboot.1                # Manpage
auto-reboot.bash_completion  # Tab completion for bash
auto-reboot.conf             # Default /etc/auto-reboot.conf
Makefile                     # install / uninstall / check / test
run_tests.sh                 # BATS test runner
tests/                       # BATS test suite (8 files + test_helper.bash)
AUDIT-BASH.md                # Code audit report
LICENSE                      # GPL-3.0
README.md                    # This file