REBOOT(8)

💅 REBOOT — System Manager's Manual (8) 🎀

okay bestie, so this is the reboot(8) page, and honestly? it's lowkey the most main-character page in the whole section 8 lineup. we're talking stopping and restarting the system — reboot, halt, fastboot, fasthalt. four icons, one purpose: turning the vibe (and the machine) off and on again. ✨

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🦋 SYNOPSIS 🦋

no cap, here's the exact shape of these commands — copy them character for character or the shell will be like "girl what":

halt [-DflNnpq] [-e variable=value] [-k kernel] [-o options]
reboot [-cDdflNnpqr] [-e variable=value] [-k kernel] [-o options]
fasthalt [-DflNnpq] [-e variable=value] [-k kernel] [-o options]
fastboot [-dDflNnpq] [-e variable=value] [-k kernel] [-o options]

notice how reboot gets the extra c and r, and fastboot gets a d? they're all just different flavors of the same energy, iykyk. 💜

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🌸 DESCRIPTION 🌸

okay so here's the tea ☕ — halt and reboot are the two that do the actual work. what they do:

• flush the file system cache to disk (gotta save your data, bestie, always)
• send all running processes a SIGTERM — that's the polite "hey, wrap it up" signal
• and subsequently a SIGKILL — that's the "okay I asked nicely" signal 💀
• then, respectively, halt or restart the system

the action is logged, and yes — that includes entering a shutdown record into the user accounting database. so the system remembers. 🙈

The options are as follows:

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✨ OPTIONS ✨

• -c — the system will turn off the power and then turn it back on if it can. if the power down action fails, the system will halt or reboot normally, depending on whether halt or reboot was called. lowkey important caveat: at the present time, only the ipmi(4) driver implements the power cycle functionality, and only on hardware with a BMC that supports power cycling. unlike power off, the amount of hardware that supports power cycling is small. so like… don't count on this one, bestie 😭
• -D — delete existing nextboot configuration and exit. that's it. it dips. 🫶
• -d — the system is requested to create a crash dump. ⚠️ this option is supported only when rebooting, and it has no effect unless a dump device has previously been specified with dumpon(8). so if you haven't set that up, this flag is literally just decorative. 💅
• -e variable=value — sets variable to value in the loader's and kernel's environment. and here's the detail nobody expects: if value is not already enclosed in double quotes, they will be added before writing to the nextboot configuration. 🎀 care should be taken if value contains any characters that are special to the shell or loader's configuration parsing code — like, be careful, fr fr.
• -f — force reboot. normally, reboot checks for the presence of the next kernel, and absence of the /var/run/noshutdown file. without this flag, reboot is denied if one of the conditions failed. so this is your "I said what I said" flag. 👑
• -k kname — boot the specified kernel kname on the next system boot. this is a one-shot option — the default kernel will be booted on successive boots. no reboot or halt will be performed if /boot/kname/kernel does not exist unless the -f flag is specified. so like, it's a one-night-only performance. 🌈
• -l — the halt or reboot is not logged to the system log. this option is intended for applications such as shutdown(8), that call reboot or halt and log this themselves. teamwork, bestie 🫶
• -N — the file system cache is not flushed during the initial process clean-up, however the kernel level reboot(2) is still processed with a sync. this can be useful for performing a "best-effort" reboot when devices might be unavailable — which can happen when devices have been disconnected, such as with iscsi(4). 🦋
• -n — the file system cache is not flushed. ⚠️ this option should probably not be used. that's the whole note. they said it, not me. 😭
• -o options — this option allows the passing of kernel flags for the next boot. ✨
• -p — the system will turn off the power if it can. if the power down action fails, the system will halt or reboot normally, depending on whether halt or reboot was called. the polite version of -c. 🎀
• -q — the system is halted or restarted quickly and ungracefully, and only the flushing of the file system cache is performed (if the -n option is not specified). ⚠️ this option should probably not be used. again — their words!! 💀
• -r — okay this one's iconic. the system kills all processes, unmounts all filesystems, mounts the new root filesystem, and begins the usual startup sequence. after changing vfs.root.mountfrom with kenv(1), reboot -r can be used to change the root filesystem while preserving kernel state. ✨ this requires the tmpfs(4) kernel module to be loaded — because init(8) needs a place to store itself after the old root is unmounted, but before the new root is in place. it's giving backstage-pass energy. 👑

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so like, fasthalt and fastboot? nothing more than aliases for the halt and reboot utilities. same girl, different name. 💅

and normally, the shutdown(8) utility is used when the system needs to be halted or restarted — giving users advance warning of their impending doom and cleanly terminating specific programs. not me quoting "impending doom" directly, that's genuinely what the page says 😭

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🌈 EXAMPLES 🌈

replace current root filesystem with UFS mounted from /dev/ada0s1a:

kenv vfs.root.mountfrom=ufs:/dev/ada0s1a
reboot -r

this mechanism can also be used with NFS, with a caveat that it only works with NFSv4, and requires a numeric IPv4 address:

kenv vfs.root.mountfrom=nfs:192.168.1.1:/share/name
reboot -r

see how it's 192.168.1.1 and not a hostname? that's the numeric IPv4 thing. don't @ me, @ the manpage. 🍓

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🧚 SEE ALSO 🧚

kenv(1), reboot(2), getutxent(3), ipmi(4), boot(8), dumpon(8), nextboot(8), savecore(8), shutdown(8), sync(8)

(go read shutdown(8) first, bestie, it's the responsible one 💜)

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⭐ HISTORY ⭐

a reboot utility appeared in 4.0BSD. ancient. iconic. still slaying. 🎀

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🫶 okay that's the whole page!! and before you close this tab — this beauty ships with Debian, and it's dated April 12, 2025. so like, recent glow-up, vintage soul. mwah 💋✨