BLOCKDEV(8)

💖 BLOCKDEV 💖

okay bestie, so this is the blockdev page from section 8 of the manual (that's the System Administration girlies, iykyk) — and literally all it does is let you call block device ioctls straight from your command line. no cap. it's giving "kernel whisperer but make it cute" ✨

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🌸 NAME 🌸

blockdev — call block device ioctls from the command line

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✨ SYNOPSIS ✨

blockdev [-q] [-v] command [command...] device [device...]

blockdev --report [device...]

blockdev -h|-V

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🦋 DESCRIPTION 🦋

The utility blockdev allows one to call block device ioctls from the command line. that's it, that's the whole vibe 🫶

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💅 OPTIONS 💅

• -q — Be quiet. shhh 🤫
• -v — Be verbose. tell me everything bestie 🗣️
• --report — Print a report for the specified device. It is possible to give multiple devices. If none is given, all devices which appear in /proc/partitions are shown. Note that the partition StartSec is in 512-byte sectors. 👑
• -h, --help — Display help text and exit.
• -V, --version — Display version and exit.

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🎀 COMMANDS 🎀

It is possible to give multiple devices and multiple commands. yes queen, stack them 🔥

• --flushbufs — Flush buffers.
• --getalignoff — Get alignment offset.
• --getbsz — Print the blocksize in bytes. This size does not describe device topology. It's the size used internally by the kernel and it may be modified (for example) by filesystem driver on mount. so like, not the whole story, just the kernel's internal number 📏
• --getdiscardzeroes — Get discard zeroes support status.
• --getdiskseq — Get disk sequence number.
• --getzonesz — Get zone size in 512-byte sectors.
• --getfra — Get filesystem readahead in 512-byte sectors.
• --getiomin — Get minimum I/O size.
• --getioopt — Get optimal I/O size.
• --getmaxsect — Get max sectors per request.
• --getpbsz — Get physical block (sector) size.
• --getra — Print readahead (in 512-byte sectors).
• --getro — Get read-only. Print 1 if the device is read-only, 0 otherwise. binary queen 💅
• --getsize64 — Print device size in bytes.
• --getsize — Print device size (32-bit!) in sectors. Deprecated in favor of the --getsz option. > lowkey retired bestie, use --getsz instead 🫶
• --getss — Print logical sector size in bytes - usually 512.
• --getsz — Get size in 512-byte sectors.
• --rereadpt — Reread partition table. refresh bestie 🔄
• --setbsz bytes — Set blocksize. Note that the block size is specific to the current file descriptor opening the block device, so the change of block size only persists for as long as blockdev has the device open, and is lost once blockdev exits. so it's giving temporary, not permanent 😭
• --setfra sectors — Set filesystem readahead (same as --setra on 2.6 kernels).
• --setra sectors — Set readahead (in 512-byte sectors).
• --setro — Set read-only. The currently active access to the device may not be affected by the change. For example, a filesystem already mounted in read-write mode will not be affected. The change applies after remount. > important bestie, this one does NOT retroactively fix a thing that's already mounted rw — you gotta remount 💀
• --setrw — Set read-write.

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💜 AUTHORS 💜

blockdev was written by Andries E. Brouwer and rewritten by Karel Zak. icons only 👑✨

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🌈 REPORTING BUGS 🌈

For bug reports, use the issue tracker <https://github.com/util-linux/util-linux/issues>. go tell them, they wanna know fr fr 🙈

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⭐ AVAILABILITY ⭐

The blockdev command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>. get you some 🎀

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and that's the whole page bestie!! 🦋 this one's from util-linux 2.42.4, dated 2026-09-21, and yeah it's the BLOCKDEV(8) girlie herself. mwah 💖💅✨