# ndctl−start−scrub(1)

[NAME](#name)\
[SYNOPSIS](#synopsis)\
[DESCRIPTION](#description)\
[EXAMPLE](#example)\
[OPTIONS](#options)\
[COPYRIGHT](#copyright)\
[SEE ALSO](#see-also)

## NAME

ndctl−start−scrub − start an Address Range Scrub (ARS) operation

## SYNOPSIS

*ndctl start−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 sysfs file (*scrub*) that when written with the string "1\n" initiates an ARS operation. The *ndctl start−scrub* operation starts an ARS, across all specified buses, and the kernel in turn proceeds to scrub every persistent memory address region on the specified buses.

## EXAMPLE

Start a scrub on all nvdimm buses in the system. The json listing report only includes the buses that support ARS operations.

```
# ndctl start-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 start 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−wait−scrub(1)](https://docs.pmem.io/ndctl-user-guide/v68/ndctl-man-pages/untitled-2), *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"