man > integritytab(5)

INTEGRITYTAB(5)                             integritytab                             INTEGRITYTAB(5)

NAME
       integritytab - Configuration for integrity block devices

SYNOPSIS
       /etc/integritytab

DESCRIPTION
       The /etc/integritytab file describes integrity protected block devices that are set up during
       system boot.

       Empty lines and lines starting with the "#" character are ignored. Each of the remaining
       lines describes one verity integrity protected block device. Fields are delimited by white
       space.

       Each line is in the form

           volume-name block-device
               [keyfile|-] [options|-]

       The first two fields are mandatory, the remaining two are optional and only required if user
       specified non-default options during integrity format.

       The first field contains the name of the resulting integrity volume; its block device is set
       up below /dev/mapper/.

       The second field contains a path to the underlying block device, or a specification of a
       block device via "UUID=" followed by the UUID, "PARTUUID=" followed by the partition UUID,
       "LABEL=" followed by the label, "PARTLABEL=" followed by the partition label.

       The third field if present contains an absolute filename path to a key file or a "-" to
       specify none. When the filename is present, the "integrity-algorithm" defaults to
       "hmac-sha256" with the key length derived from the number of bytes in the key file. At this
       time the only supported integrity algorithm when using key file is hmac-sha256. The maximum
       size of the key file is 4096 bytes.

       The fourth field, if present, is a comma-delimited list of options or a "-" to specify none.
       The following options are recognized:

       allow-discards
           Allow the use of discard (TRIM) requests for the device. This option is available since
           the Linux kernel version 5.7.

           Added in version 250.

       mode=(journal|bitmap|direct)
           Enable journaled, bitmapped or direct (passthrough) mode. Journaled mode is the default
           when this option is not specified. It provides safety against crashes, but can be slow
           because all data has to be written twice. Bitmap mode is more efficient since it requires
           only a single write, but it is less reliable because if data corruption happens when the
           machine crashes, it may not be detected. Direct mode disables the journal and the bitmap.
           Corresponds to the "direct writes" mode documented in the dm-integrity documentation[1].
           Note that without a journal, if there is a crash, it is possible that the integrity tags
           and data will not match. If used, the journal-* options below will have no effect if
           passed.

           Added in version 254.

       journal-watermark=[0..100]%
           Journal watermark in percent. When the journal percentage exceeds this watermark, the
           journal flush will be started. Setting a value of "0%" uses default value.

           Added in version 250.

       journal-commit-time=[0..N]
           Commit time in milliseconds. When this time passes (and no explicit flush operation was
           issued), the journal is written. Setting a value of zero uses default value.

           Added in version 250.

       data-device=/dev/disk/by-...
           Specify a separate block device that contains existing data. The second field specified
           in the integritytab for block device then will contain calculated integrity tags and
           journal for data-device, but not the end user data.

           Added in version 250.

       integrity-algorithm=[crc32c|crc32|sha1|sha256|hmac-sha256]
           The algorithm used for integrity checking. The default is crc32c. Must match option used
           during format.

           Added in version 250.

       At early boot and when the system manager configuration is reloaded, this file is translated
       into native systemd units by systemd-integritysetup-generator(8).

EXAMPLES
       Example 1. /etc/integritytab

       Set up two integrity protected block devices.

           home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8 - journal-commit-time=10,allow-discards,journal-watermark=55%
           data PARTUUID=5d4b1808-be76-774d-88af-03c4c3a41761 - allow-discards

       Example 2. /etc/integritytab

       Set up 1 integrity protected block device using defaults

           home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8

       Example 3. /etc/integritytab

       Set up 1 integrity device using existing data block device which contains user data

           home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8 - data-device=/dev/disk/by-uuid/9276d9c0-d4e3-4297-b4ff-3307cd0d092f

       Example 4. /etc/integritytab

       Set up 1 integrity device using a HMAC key file using defaults

           home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8 /etc/hmac.key

SEE ALSO
       systemd(1), systemd-integritysetup@.service(8), systemd-integritysetup-generator(8),
       integritysetup(8),

NOTES
        1. the dm-integrity documentation
           https://docs.kernel.org/admin-guide/device-mapper/dm-integrity.html

systemd 255                                                                          INTEGRITYTAB(5)