LLAPI_CREATE_VOLATILE_PARAM(3)

💖 NAME 💖

llapi_create_volatile_param — bestie, this is the Lustre API file management page, and it's giving "make a file that ghosts everyone" energy 👻✨

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🌸 SYNOPSIS 🌸

#include <lustre/lustreapi.h>

int llapi_create_volatile_param(const char *directory, int mdt_indx,
                                int open_flags, mode_t mode,
                                const struct llapi_stripe_param *stripe_param)

int llapi_create_volatile_idx(char *directory, int idx, int open_flags)

int llapi_create_volatile(char *directory, int mode)

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✨ DESCRIPTION ✨

Okay so these three functions are the trio we're obsessed with. They make an anonymous, temporary, volatile file on a Lustre filesystem. The file they create? not visible with ls(1). Like, it literally will not show up. Not me making files nobody can see 💅. And the second you close the file — or the process that owns it just... dies — the file is permanently removed from the filesystem. Gone. Poof. Periodt.

Lowkey cute fact: these functions also work on a non-Lustre filesystem too. But over there it's not the same vibe — the file gets created and then unlinked, so all you've got left is the file descriptor to access it with. And why is that not strictly equivalent? Because there's a small window during which the file is visible to users (as long as they have access to the directory). So not the stealth mode you get on Lustre, iykyk 🙈.

• The directory parameter tells you where to create the file on the Lustre filesystem.
• mdt_idx is the MDT index onto which to create the file. Wanna use a default MDT? Set mdt_idx to -1. Easy.
• open_flags and mode are the same as open(2) — no new rules, same as always.
• stripe_param describes the striping information. If it's NULL, then the default for the directory is used. Simple as that 🎀.

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🫶 RETURN VALUE 🫶

llapi_create_volatile_param, llapi_create_volatile_idx and llapi_create_volatile all return a file descriptor on success — slay. And on failure? All three return a negative errno. Every single one of them.

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😭 ERRORS 😭

The negative errno can be (but is not limited to):

• -EINVAL — an invalid value was passed. Something in there was not it, bestie.
• -ENOMEM — not enough memory to allocate a resource. The machine is out here struggling, fr fr.

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👑 AUTHORS 👑

Frank Zago for Cray Inc. — iconic work, no cap 🫡

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🌈 AVAILABILITY 🌈

llapi_create_volatile_param(), llapi_create_volatile_idx() and llapi_create_volatile() are part of the lustre(7) user application interface library since release 2.4.0. So if you're on anything older, that's a vibe check fail, sorry 🧚

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⭐ SEE ALSO ⭐

• lustreapi(7)

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And that's the whole page, bestie! 💜 This was the Lustre Library Functions manual — aka LLAPI_CREATE_VOLATILE_PARAM(3) — brought to you by the Lustre User API, dated 2024-08-23. Go forth and make invisible files, you main character 🦋✨💖