> For the complete documentation index, see [llms.txt](https://docs.pmem.io/ndctl-user-guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.pmem.io/ndctl-user-guide/v71.1/ndctl-man-pages/untitled-2.md).

# ndctl−wait−scrub(1)

[NAME](/ndctl-user-guide/v71.1/ndctl-man-pages/untitled-2.md#name)\
[SYNOPSIS](/ndctl-user-guide/v71.1/ndctl-man-pages/untitled-2.md#synopsis)\
[DESCRIPTION](/ndctl-user-guide/v71.1/ndctl-man-pages/untitled-2.md#description)\
[EXAMPLE](/ndctl-user-guide/v71.1/ndctl-man-pages/untitled-2.md#example)\
[OPTIONS](/ndctl-user-guide/v71.1/ndctl-man-pages/untitled-2.md#options)\
[COPYRIGHT](/ndctl-user-guide/v71.1/ndctl-man-pages/untitled-2.md#copyright)\
[SEE ALSO](/ndctl-user-guide/v71.1/ndctl-man-pages/untitled-2.md#see-also)

## NAME

ndctl−wait−scrub − wait for an Address Range Scrub (ARS) operation to complete

## SYNOPSIS

*ndctl wait−scrub* \[\<bus-id> \<bus-id2> .. \<bus-idN>] \[\<options>]

## DESCRIPTION

NVDIMM Address Range Scrub is a capability provided by platform firmware that allows for the discovery of memory errors by system software. It enables system software to pre−emptively avoid accesses that could lead to uncorrectable memory error handling events, and it otherwise allows memory errors to be enumerated.

The kernel provides a POLL(2) capable sysfs file (*scrub*) to indicate the state of ARS. The *scrub* file maintains a running count of ARS runs that have taken place. While a current run is in progress a *+* character is emitted along with the current count. The *ndctl wait−scrub* operation waits for *scrub*, across all specified buses, to indicate not in−progress at least once.

## EXAMPLE

Wait for scrub on all nvdimm buses in the system. The json listing report at the end only includes the buses that support ARS operations.

```
# ndctl wait-scrub
[
 {
   "provider":"nfit_test.1",
   "dev":"ndbus3",
   "scrub_state":"active"
 },
 {
   "provider":"nfit_test.0",
   "dev":"ndbus2",
   "scrub_state":"active"
 }
]
```

When specifying an individual bus, or if there is only one bus in the system, the command reports whether ARS support is available.

```
# ndctl start−scrub e820
error starting scrub: Operation not supported
```

## OPTIONS

−v, −−verbose

Emit debug messages for the ARS wait process

## COPYRIGHT

Copyright (c) 2016 − 2019, Intel Corporation. License GPLv2: GNU GPL version 2 <http://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.

## SEE ALSO

[ndctl−start−scrub(1)](/ndctl-user-guide/v71.1/ndctl-man-pages/ndctl-start-scrub.md), *ACPI* <http://www.uefi.org/sites/default/files/resources/ACPI%206_2_A_Sept29.pdf> 6.2 Specification Section 9.20.7.2 Address Range Scrubbing (ARS) Overview"