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`shutdown(1b)` on Solnix vs Linux and the BSDs

The Solnix page documents the BSD-style /usr/ucb/shutdown, which takes -f -h -k -n -r and a time. Its -k only simulates a shutdown, while on FreeBSD, OpenBSD and NetBSD -k kicks users off and disables logins. It has no power-off flag (-p or -P).

The manual pages

Solnix: shutdown(1b) from pkgs.solnix.illumos-world-man · illumos.org
Linux: shutdown(8) sysvinit-3.04
FreeBSD: shutdown(8) 15.1-RELEASE
OpenBSD: shutdown(8) 8.0
NetBSD: shutdown(8) 11.0

What Solnix runs

The page describes /usr/ucb/shutdown, which ships with Solnix. The command on PATH by default is the illumos /usr/sbin/shutdown, and the bundle does not include its text. Do not assume the two take the same options. Check shutdown(8) for /usr/sbin/shutdown before scripting against it.

Differences

Compared with	Topic	What differs
FreeBSD, OpenBSD, NetBSD	`-k` meaning	Solnix `-k` simulates a shutdown and does nothing to the system. On FreeBSD, OpenBSD and NetBSD, `-k` kicks everybody off: the system stays multi-user with logins disabled for all but the superuser. Source: Solnix shutdown(1b) -k; FreeBSD shutdown(8) -k; OpenBSD shutdown(8) -k; NetBSD shutdown(8) -k
Linux	`-k` meaning	Solnix `-k` simulates the shutdown. Linux `-k` also does not shut down, but it only sends the warning messages to everybody. Source: Solnix shutdown(1b) -k; Linux shutdown(8) -k
FreeBSD	`-f` meaning	Solnix `-f` arranges, as fastboot(1B) does, that file systems are not checked at the next reboot. FreeBSD `-f` makes shutdown ignore the `/var/run/noshutdown` file. It has nothing to do with fsck. Source: Solnix shutdown(1b) -f; FreeBSD shutdown(8) -f
Linux, OpenBSD, NetBSD	`-f` and fsck	Linux `-f` and OpenBSD `-f` create /fastboot to skip fsck at the next boot. NetBSD `-f` works as fastboot(8) does. Linux also has `-F`, which creates /forcefsck to force a check. Solnix has no `-F`. Source: Linux shutdown(8) -f, -F; OpenBSD shutdown(8) -f; NetBSD shutdown(8) -f; Solnix shutdown(1b) -f
all four	no power-off flag	The Solnix page has no `-p` or `-P`. Its `-h` only executes halt(8), and the page does not say whether power is turned off. FreeBSD, OpenBSD and NetBSD use `-p` to power down, and Linux uses `-h` `-P`. Source: Solnix shutdown(1b) SYNOPSIS, -h; Linux shutdown(8) -P; FreeBSD shutdown(8) -p; OpenBSD shutdown(8) -p; NetBSD shutdown(8) -p
Linux, FreeBSD	`-n` meaning	Solnix `-n` skips the normal sync(2) before stopping. Linux `-n` (deprecated) makes shutdown kill processes itself instead of calling init(8). FreeBSD `-n` only works with `-o` and passes `-n` to halt(8) or reboot(8). Source: Solnix shutdown(1b) -n; Linux shutdown(8) -n; FreeBSD shutdown(8) -o, -n
OpenBSD, NetBSD	`-n` meaning	Solnix `-n`, OpenBSD `-n` and NetBSD `-n` all prevent the normal sync(2) before stopping. OpenBSD documents it as applying with `-h`, `-p` or `-r`. Source: Solnix shutdown(1b) -n; OpenBSD shutdown(8) -n; NetBSD shutdown(8) -n
all four	time argument formats	Solnix accepts now, +number (minutes) and hour:min in 24-hour notation, and only up to 23:59 today. Linux adds +hh:mm. FreeBSD allows date forms and unit suffixes. OpenBSD uses yymmddhhmm. NetBSD uses [[[[[cc]yy]mm]dd]hh]mm. Source: Solnix shutdown(1b) DESCRIPTION, NOTES; Linux shutdown(8); FreeBSD shutdown(8) time; OpenBSD shutdown(8) time; NetBSD shutdown(8) time
NetBSD	colon in time	Solnix takes hour:min with a colon. The NetBSD time format has no colon, and its page does not mention one. FreeBSD and OpenBSD accept a colon only as backward compatibility. Source: Solnix shutdown(1b) DESCRIPTION; NetBSD shutdown(8) time; FreeBSD shutdown(8) COMPATIBILITY; OpenBSD shutdown(8) STANDARDS
FreeBSD, OpenBSD, NetBSD	message from stdin	FreeBSD, OpenBSD and NetBSD read the warning message from standard input when given '-'. The Solnix synopsis has no '-', and its warning message must be on the command line. Source: Solnix shutdown(1b) SYNOPSIS; FreeBSD shutdown(8) '-'; OpenBSD shutdown(8) '-'; NetBSD shutdown(8) '-'
Linux, FreeBSD, OpenBSD	login blocking and cancelling	Linux, FreeBSD and OpenBSD create a nologin file before the shutdown (`/etc/nologin` on Linux and OpenBSD, `/var/run/nologin` on FreeBSD). The Solnix page mentions none. Linux cancels with `-c`. FreeBSD and OpenBSD cancel by killing the shutdown process. The Solnix page says nothing about cancelling. Source: Linux shutdown(8) -c, /etc/nologin; FreeBSD shutdown(8) /var/run/nologin; OpenBSD shutdown(8) /etc/nologin; Solnix shutdown(1b) DESCRIPTION
all four	options missing on Solnix	Solnix has none of these: Linux `-a` `-c` `-q` `-Q` `-t` and `-H`. FreeBSD `-c` `-o` `-q`. OpenBSD `-d`. NetBSD `-b` `-d` `-D` `-v` `-x` `-z`. A script using any of them fails on the Solnix `/usr/ucb/shutdown.` Source: Solnix shutdown(1b) SYNOPSIS; option lists in Linux, FreeBSD, OpenBSD and NetBSD shutdown(8)

Everyday tasks

Task	Solnix	Linux	FreeBSD	OpenBSD	NetBSD
reboot immediately	`shutdown -r now`	`shutdown -r now`	`shutdown -r now`	`shutdown -r now`	`shutdown -r now`
halt immediately	`shutdown -h now`	`shutdown -h -H now`	`shutdown -h now`	`shutdown -h now`	`shutdown -h now`
power off immediately	—	`shutdown -h -P now`	`shutdown -p now (or poweroff)`	`shutdown -p now`	`shutdown -p now`
cancel a scheduled shutdown	—	`shutdown -c`	`kill the shutdown process`	`kill the shutdown process`	—

Standards

POSIX: shutdown is not a POSIX.1-2024 utility.
Solnix: The shutdown(1b) page in the bundle has no ATTRIBUTES or STANDARDS section.
OpenBSD: The STANDARDS section only says that a colon between hours and minutes in the second time format is accepted for backward compatibility. It names no standard.
FreeBSD: The COMPATIBILITY section says hh:mm is accepted as equivalent to hhmm. No standard is named.
Linux: The Linux page (sysvinit) in the bundle names no standard.
NetBSD: The NetBSD page in the bundle names no standard.

Writing portable scripts

Use only -r with 'now' (shutdown -r now) in portable scripts. -h, -k, -f, -n and the power-off flags differ across Solnix, Linux and the BSDs.
Always give a time argument, such as now. Linux says it is mandatory, and every synopsis in the bundle shows it.
Select the power-off flag per system: -P on Linux, -p on the BSDs. The Solnix /usr/ucb/shutdown page documents neither.

Every difference here is taken from the manual pages linked above: Solnix's published page, Linux (man-pages and the GNU and util-linux manuals), FreeBSD, OpenBSD and NetBSD. Each row names its source. Where a manual is silent, this page is too. Compiled 2026-10-26. Found a mistake? Mail hackers@lists.solnix.io.

shutdown(1b) on Solnix vs Linux and the BSDs