LLAPI\_CHANGELOG\_DEREGISTER(3) Lustre Library Functions LLAPI\_CHANGELOG\_DEREGISTER(3)

# [NAME](#NAME)

llapi\_changelog\_deregister - Deregister changelog user on specific MDT device

# [SYNOPSIS](#SYNOPSIS)

```
#include <lustre/lustreapi.h>
```

```
int llapi_changelog_deregister(const char *mdtname, const char *regname);
```

# [DESCRIPTION](#DESCRIPTION)

The function **llapi\_changelog\_deregister()** deregisters changelog *regname* on specific MDT device *mdtname* (e.g. **lustrefs-MDT0000**). It must be run on the MDS node where the MDT is currently mounted.

The *regname* argument preferably uses the *username* specified during [*llapi\_changelog\_register*(3)](/man/enterprise-packages/lustre/llapi_changelog_register.3) (e.g. '**audit**') as this allows an application to deregister its changelog user by the preferred name regardless of which changelog user number was assigned, but it can also be the changelog user number (e.g. '**cl4**' or '**4**'), or both (e.g. '**cl4-audit**').

# [RETURN VALUES](#RETURN_VALUES)

Return 0 on success or a negative errno value on failure.

# [ERRORS](#ERRORS)

-EINVAL

MDT device is invalid or not found.

-ENOENT

Username is not found.

# [EXAMPLE](#EXAMPLE)

To deregister a previously-registered changelog user:

```
#include <lustre/lustreapi.h>
int main(int argc, char *argv[])
{
	char *mdtname = argv[1]; /* e.g. "testfs-MDT0000" */
	char *username = argv[2]; /* e.g. "cl4-audit" */
	int rc;
	rc = llapi_changelog_deregister(mdtname, username);
}
```

# [AVAILABILITY](#AVAILABILITY)

**llapi\_changelog\_deregister()** is part of the [**lustre**(7)](/man/enterprise-packages/lustre/lustre.7) user application interface library since release 2.18.0

# [SEE ALSO](#SEE_ALSO)

[**llapi\_changelog\_register**(3)](/man/enterprise-packages/lustre/llapi_changelog_register.3), [**lustreapi**(7)](/man/enterprise-packages/lustre/lustreapi.7), [**lctl-changelog\_deregister**(8)](/man/enterprise-packages/lustre/lctl-changelog_deregister.8)

2026-09-12 Lustre User API

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Document: llapi_changelog_deregister(3) from lustre 2.17.60-r0 (Chainguard OS)
Source: https://github.com/lustre/lustre-release