FWUP(1)

👑 fwup(1) — like, the manual page, bestie ✨

okay so before we even get into it: this is fwup, it lives in the User Commands corner of the manual-verse, and it's genuinely one of those tools that ate and left no crumbs 💅. Let's get into it fr fr.

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🌸 NAME 🌸

fwup — the configurable embedded firmware update creator and runner. yes, both. she does it all 🫶

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✨ SYNOPSIS ✨

fwup [OPTION]...

that's it. that's the whole vibe. options go in, firmware magic comes out 🎀

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🦋 DESCRIPTION 🦋

so fwup is a self-contained utility for creating and applying firmware update files. and like — what even is a firmware update file? bestie, listen: .fw files are literally nothing more than zip archives containing metadata, a limited set of instructions, and data. no cap. that's the whole secret 🤫

and where does it run? on an embedded device or on a host PC — either one, she's flexible like that 😌. fwup is used to write nonvolatile memory (eMMC, SDCards, etc.) in such a way as to upgrade the firmware on the device, or to completely initialize it. it's giving main character energy for your storage media, honestly 👑

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💖 OPTIONS 💖

like yes there are a lot of them, but each one is iconic in her own way:

• -a, --apply — applies the firmware update. do the thing 🔥
• -c, --create — creates the firmware update. make the thing 🎀
• -d <file> — the device file for the memory card
• -D, --detect — lists attached SDCards or MMC devices, plus their sizes. a little headcount for your hardware 💅
• -E, --eject — ejects removable media after successfully writing firmware
• --no-eject — do not eject media after writing firmware
• --enable-trim — enables use of the hardware TRIM command ✨
• --exit-handshake — sends a Ctrl+Z on exit and waits for stdin to close (Erlang)
• -f <fwup.conf> — specifies the firmware update configuration file
• -F, --framing — applies framing on stdin/stdout
• -g, --gen-keys — generates firmware signing keys (fwup-key.pub and fwup-key.priv, or specify with -o)
• -i <input.fw> — specifies the input firmware update file (use - for stdin)
• -l, --list — lists the available tasks in a firmware update 🗒️
• --max-size <blocks> — max size of the destination in 512-byte blocks (usually automatic)
• -m, --metadata — prints metadata in the firmware update
• --metadata-key <key> — only outputs the specified key's value when printing metadata
• --minimize-writes — skips the write if contents match the destination. savings, queen 💸
• --no-minimize-writes — doesn't try to minimize writes when applying firmware updates (default)
• -n — reports numeric progress
• -o <output.fw> — specifies the output file when creating an update (use - for stdout)
• -p, --public-key-file <keyfile> — a public key file for verifying firmware updates (can specify multiple times)
• --private-key <key> — a private key for signing firmware updates
• --progress-low <number> — when displaying progress, this is the lowest number (normally 0 for 0%)
• --progress-high <number> — when displaying progress, this is the highest number (normally 100 for 100%)
• --public-key <key> — a public key for verifying firmware updates (can specify multiple times)
• -q, --quiet — quiet 🤐
• --reboot-param-path — path to write reboot parameters (defaults to systemd and Nerves locations)
• -s, --private-key-file <keyfile> — a private key file for signing firmware updates
• -S, --sign — signs an existing firmware file (specify -i and -o)
• --sparse-check <path> — checks if the OS and file system support sparse files at path
• --sparse-check-size <bytes> — hole size to check for --sparse-check
• -t, --task <task> — task to apply within the firmware update
• -u, --unmount — unmounts all partitions on the device first
• -U, --no-unmount — does not try to unmount partitions on the device
• --unsafe — allows unsafe commands (consider applying only signed archives ⚠️)
• -v, --verbose — verbose 🗣️
• -V, --verify — verifies an existing firmware file (specify -i)
• --verify-writes — verifies writes when applying firmware updates to detect corruption (default for writing to device files)
• --no-verify-writes — does not verify writes when applying firmware updates (default for regular files)
• --version — prints out the version
• -y — accepts automatically found memory card when applying a firmware update
• -z — prints the memory card that would be automatically detected, then exits
• -1 — fast compression (for create)
• -9 — best compression (default)

lowkey important: --unsafe literally says allow unsafe commands in the description, and it comes with the parenthetical advice to consider applying only signed archives. read that twice, bestie 🙈

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🌈 EXAMPLES 🌈

initialize an attached SDCard using all of the default options:

$ fwup myfirmware.fw

create a firmware update archive:

$ fwup -c -f fwup.conf -o myfirmware.fw

apply the firmware to an attached SDCard

this would normally be run on the host, where it would auto-detect an SDCard and initialize it using the complete task:

$ fwup -a -i myfirmware.fw -t complete

apply the firmware update to /dev/sdc and specify the upgrade task:

$ fwup -a -d /dev/sdc -i myfirmware.fw -t upgrade

create an image file from a .fw file for use with dd(1):

$ fwup -a -d myimage.img -i myfirmware.fw -t complete

generate a public/private key pair:

$ fwup -g

store fwup-key.priv in a safe place 🔐 and fwup-key.pub on the target. to sign an existing archive, run:

$ fwup -S -s fwup-key.priv -i myfirmware.fw -o signedfirmware.fw

also see the unit tests that come with fwup source code for more examples 👀. obtain source code and report bugs at https://github.com/fwup-home/fwup.

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🧚 AUTHOR 🧚

Written by Frank Hunleth.

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💀 REPORTING BUGS 💀

please report any bugs on the project page at <https://github.com/fwup-home/fwup> 🫶

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not the bug-report section being the shortest one 😭 anyway

okay that's the whole page, you ate that ngl 💜 — this was fwup version 1.15.0, dated March 2026, and that's the FWUP(1) manual page, periodt. 🌸✨🎀