blkmapd(8)

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💅 blkmapd — the pNFS block layout mapping daemon, bestie edition 💅

okay so real talk, this is a page from the System Manager's Manual, section 8, and it's about a little daemon called blkmapd. she's the pNFS block layout mapping daemon and honestly? she's doing the most so your kernel doesn't have to. let's get into it ✨

🌸 NAME 🌸

blkmapd — pNFS block layout mapping daemon. that's her. that's the whole name. iconic.

🦋 SYNOPSIS 🦋

blkmapd [-h] [-d] [-f]

three little flags, that's it, she's low maintenance 💖

✨ DESCRIPTION ✨

The blkmapd daemon performs device discovery and mapping for the parallel NFS (pNFS) block layout client [RFC5663]. like, she goes out there and finds your devices and figures out the mapping situation. that's the job. no cap.

The pNFS block layout protocol builds a complex storage hierarchy from a set of simple volumes. These simple volumes are addressed by content, using a signature on the volume to uniquely name each one. so like — a volume's whole identity? it's the signature, not some boring address. The daemon locates a volume by examining each block device in the system for the given signature. she is literally checking every single block device in the system until she finds the one with the matching signature. the dedication. the commitment. we love to see it 🫶

The topology typically consists of a hierarchy of volumes built by striping, slicing, and concatenating the simple volumes. The blkmapd daemon uses the device-mapper driver to construct logical devices that reflect the server topology, and passes these devices to the kernel for use by the pNFS block layout client. so she's out here building logical devices with the device-mapper driver that mirror what the server's topology looks like, and then handing them straight to the kernel like "here bestie, use these 💅". main character energy fr fr.

🎀 OPTIONS 🎀

  • -h — Display usage message. aka "how does this work" mode 🙈
  • -d — Performs device discovery only then exits. she does the discovery, says "k bye", and dips. no mapping, just the search 👑
  • -f — Runs blkmapd in the foreground and sends output to stderr (as opposed to syslogd). no backgrounding, no syslog — everything comes straight at you on stderr ⭐

🌈 CONFIGURATION FILE 🌈

The blkmapd daemon recognizes the following value from the [general] section of the /etc/nfs.conf configuration file:

  • pipefs-directory — Tells blkmapd where to look for the rpc_pipefs filesystem. The default value is /var/lib/nfs/rpc_pipefs. so if your rpc_pipefs lives somewhere else, this is where you tell her. otherwise she assumes the default 🧚

💜 SEE ALSO 💜

RFC 5661 for the NFS version 4.1 specification.

RFC 5663 for the pNFS block layout specification.

like, go read them, iykyk 📚

🍓 AUTHORS 🍓

  • Haiying Tang <Tang_Haiying@emc.com>
  • Jim Rees <rees@umich.edu>

two absolute legends. thank you for your service 🫡💖

and that's the whole page, bestie!! this one's dated 11 August 2011 and it comes to you from the System Manager's Manual — so yeah, she's been out here slaying since 2011 and honestly she hasn't aged a day. 💅✨🌸🦋🎀

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