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# dm-integrity

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The dm-integrity kernel device mapper target provides an additional layer with per-sector integrity information. In standalone mode it supports CRC (CRC-32, CRC-32C) or hash functions (xxHash64, SHA-1, SHA-256). It can also be used with dm-crypt to provide authenticated disk encryption with HMAC-SHA256. It uses journaling for guaranteeing write atomicity by default, which effectively halves the write speed.

## Usage

The main utility for standalone management is integritysetup, included in the cryptsetup package. The dm-integrity layer can also be activated and managed with the cryptsetup utility or with LVM. This section covers management in standalone mode.

### Format

The underlying device/partition/volume has to be formatted and the initial integrity metadata written, which takes some time. The integrity algorithm `algo` can be one of `crc32c`, `crc32`, `xxhash64`, `sha1` or `sha256`.

    # integritysetup format -v --integrity algo /dev/device

### Open

A dm-integrity-protected volume is opened with:

    # integritysetup open -v --integrity algo /dev/device volname

Afterwards the volume can be accessed through `/dev/mapper/volname`.

### Close

After all contained filesystems are unmounted the volume is closed with:

    # integritysetup close -v volname

### /etc/integritytab

The `/etc/integritytab` file can be set up to open specific volumes at system boot. See integritytab(5).

## See also

- integritysetup(8)
- cryptsetup(8)
- dm-integrity kernel documentation

Category:

- Security