cryptsetup

CRYPTSETUP(8)                Maintenance Commands                CRYPTSETUP(8)

NAME
       cryptsetup - manage plain dm-crypt and LUKS encrypted volumes

SYNOPSIS
       cryptsetup <options> <action> <action args>

DESCRIPTION
       cryptsetup is used to conveniently setup dm-crypt managed device-mapper
       mappings. These include plain dm-crypt volumes and  LUKS  volumes.  The
       difference is that LUKS uses a metadata header and can hence offer more
       features than plain dm-crypt. On the other hand, the header is  visible
       and vulnerable to damage.

       In  addition,  cryptsetup provides limited support for the use of loop-
       AES volumes and for TrueCrypt compatible volumes.

PLAIN DM-CRYPT OR LUKS?
       Unless you understand the  cryptographic  background  well,  use  LUKS.
       With  plain  dm-crypt  there  are a number of possible user errors that
       massively decrease security. While LUKS cannot fix  them  all,  it  can
       lessen the impact for many of them.

WARNINGS
       A  lot  of good information on the risks of using encrypted storage, on
       handling problems and on security aspects can be found  in  the  Crypt-
       setup  FAQ.  Read  it.  Nonetheless, some risks deserve to be mentioned
       here.

       Backup: Storage media die. Encryption has no influence on that.  Backup
       is mandatory for encrypted data as well, if the data has any worth. See
       the Cryptsetup FAQ for advice on how to do a  backup  of  an  encrypted
       volume.

       Character encoding: If you enter a passphrase with special symbols, the
       passphrase can change depending on character  encoding.  Keyboard  set-
       tings  can  also change, which can make blind input hard or impossible.
       For example, switching from some ASCII 8-bit variant to UTF-8 can  lead
       to  a  different binary encoding and hence different passphrase seen by
       cryptsetup, even if what you see on the terminal is exactly  the  same.
       It is therefore highly recommended to select passphrase characters only
       from 7-bit ASCII, as the encoding for 7-bit ASCII stays  the  same  for
       all ASCII variants and UTF-8.

       LUKS  header:  If the header of a LUKS volume gets damaged, all data is
       permanently lost unless you have a header-backup.   If  a  key-slot  is
       damaged,  it  can  only  be restored from a header-backup or if another
       active key-slot with known passphrase is undamaged.  Damaging the  LUKS
       header is something people manage to do with surprising frequency. This
       risk is the result of a trade-off between security and safety, as  LUKS
       is  designed  for fast and secure wiping by just overwriting header and
       key-slot area.

       Previously used partitions: If a partition was previously used, it is a
       very  good idea to wipe filesystem signatures, data, etc. before creat-
       ing a LUKS or plain dm-crypt container on it.  For a quick  removal  of
       filesystem signatures, use "wipefs". Take care though that this may not
       remove everything. In particular, MD RAID signatures at the  end  of  a
       device  may  survive.  It  also  does not remove data. For a full wipe,
       overwrite the whole partition before container creation. If you do  not
       know how to do that, the cryptsetup FAQ describes several options.

BASIC COMMANDS
       The following are valid actions for all supported device types.

       open <device> <name> --type <device_type>

              Opens (creates a mapping with) <name> backed by device <device>.

              Device type can be plain, luks (default), loopaes or tcrypt.

              For backward compatibility there are open command aliases:

              create (argument-order <name> <device>): open --type plain
              plainOpen: open --type plain
              luksOpen: open --type luks
              loopaesOpen: open --type loopaes
              tcryptOpen: open --type tcrypt

              <options> are type specific and are described below for individ-
              ual device types. For  create,  the  order  of  the  <name>  and
              <device>  options  is inverted for historical reasons, all other
              aliases use the standard <device> <name> order.

       close <name>

              Removes the existing mapping <name> and wipes the key from  ker-
              nel memory.

              For  backward  compatibility  there  are  close command aliases:
              remove, plainClose, luksClose,  loopaesClose,  tcryptClose  (all
              behaves  exactly  the  same, device type is determined automati-
              cally from active device).

              <options> can be [--deferred]

       status <name>

              Reports the status for the mapping <name>.

       resize <name>

              Resizes an active mapping <name>.

              If --size (in 512-bytes sectors) is not specified, the  size  is
              computed  from the underlying device. For LUKS it is the size of
              the underlying device without the area reserved for LUKS  header
              (see  data payload offset in luksDump command).  For plain crypt
              device, the whole device size is used.

              Note that this does not change the raw device geometry, it  just
              changes  how  many  sectors of the raw device are represented in
              the mapped device.

              If cryptsetup detected volume key for active  device  loaded  in
              kernel  keyring  service,  resize  action  would  first  try  to
              retrieve the key using a token and only if it  failed  it'd  ask
              for  a passphrase to unlock a keyslot (LUKS) or to derive a vol-
              ume key again (plain mode).   The  kernel  keyring  is  used  by
              default for LUKS2 devices.

              With  LUKS2  device  additional  <options>  can  be [--token-id,
              --token-only,  --key-slot,  --key-file,  --keyfile-size,  --key-
              file-offset, --timeout, --disable-locks, --disable-keyring].

PLAIN MODE
       Plain dm-crypt encrypts the device sector-by-sector with a single, non-
       salted hash of the passphrase. No checks are performed, no metadata  is
       used.  There is no formatting operation.  When the raw device is mapped
       (opened), the usual device operations can be used on the mapped device,
       including  filesystem  creation.   Mapped  devices  usually  reside  in
       /dev/mapper/<name>.

       The following are valid plain device type actions:

       open --type plain <device> <name>
       create <name> <device> (OBSOLETE syntax)

              Opens (creates a mapping with) <name> backed by device <device>.

              <options> can be [--hash, --cipher, --verify-passphrase,  --sec-
              tor-size,  --key-file,  --keyfile-offset,  --key-size, --offset,
              --skip, --size, --readonly, --shared, --allow-discards]

              Example: 'cryptsetup open --type plain /dev/sda10 e1'  maps  the
              raw encrypted device /dev/sda10 to the mapped (decrypted) device
              /dev/mapper/e1, which can then be mounted,  fsck-ed  or  have  a
              filesystem created on it.

LUKS EXTENSION
       LUKS,  the  Linux Unified Key Setup, is a standard for disk encryption.
       It adds a standardized header at the start of the  device,  a  key-slot
       area directly behind the header and the bulk data area behind that. The
       whole set is called a 'LUKS container'.  The device that  a  LUKS  con-
       tainer  resides  on is called a 'LUKS device'.  For most purposes, both
       terms can be used interchangeably. But note that when the  LUKS  header
       is  at  a  nonzero  offset  in  a device, then the device is not a LUKS
       device anymore, but has a LUKS container stored in it at an offset.

       LUKS can manage multiple passphrases that can be  individually  revoked
       or  changed and that can be securely scrubbed from persistent media due
       to the use of anti-forensic stripes. Passphrases are protected  against
       brute-force  and  dictionary  attacks  by PBKDF2, which implements hash
       iteration and salting in one function.

       LUKS2 is a new version of header format that allows  additional  exten-
       sions  like different PBKDF algorithm or authenticated encryption.  You
       can format device with LUKS2 header if  you  specify  --type  luks2  in
       luksFormat  command.   For activation, the format is already recognized
       automatically.

       Each passphrase, also called a key in this document, is associated with
       one  of  8 key-slots.  Key operations that do not specify a slot affect
       the first slot that matches the supplied passphrase or the first  empty
       slot if a new passphrase is added.

       The <device> parameter can also be specified by a LUKS UUID in the for-
       mat UUID=<uuid>. Translation to  real  device  name  uses  symlinks  in
       /dev/disk/by-uuid directory.

       To specify a detached header, the --header parameter can be used in all
       LUKS commands and always takes precedence over the positional  <device>
       parameter.

       The following are valid LUKS actions:

       luksFormat <device> [<key file>]

              Initializes  a  LUKS  partition  and sets the initial passphrase
              (for key-slot 0), either via prompting or via <key  file>.  Note
              that  if  the second argument is present, then the passphrase is
              taken from the file given there, without the  need  to  use  the
              --key-file  option. Also note that for both forms of reading the
              passphrase from a file you can give  '-'  as  file  name,  which
              results  in the passphrase being read from stdin and the safety-
              question being skipped.

              You can only call luksFormat  on  a  LUKS  device  that  is  not
              mapped.

              To use LUKS2, specify --type luks2.

              <options>   can   be   [--hash,  --cipher,  --verify-passphrase,
              --key-size,  --key-slot,  --key-file  (takes   precedence   over
              optional  second  argument),  --keyfile-offset,  --keyfile-size,
              --use-random   |   --use-urandom,   --uuid,   --master-key-file,
              --iter-time,  --header,  --pbkdf-force-iterations, --force-pass-
              word, --disable-locks].

              For   LUKS2,   additional   <options>   can   be   [--integrity,
              --integrity-no-wipe,    --sector-size,   --label,   --subsystem,
              --pbkdf,  --pbkdf-memory,   --pbkdf-parallel,   --disable-locks,
              --disable-keyring].

              WARNING:  Doing  a luksFormat on an existing LUKS container will
              make all data the old container permanently irretrievable unless
              you have a header backup.

       open --type luks <device> <name>
       luksOpen <device> <name> (old syntax)

              Opens  the  LUKS  device  <device>  and sets up a mapping <name>
              after successful verification of the supplied passphrase.

              First, the passphrase is searched in LUKS tokens.  If  it's  not
              found  in  any token and also the passphrase is not supplied via
              --key-file, the command prompts for it interactively.

              <options> can be [--key-file, --keyfile-offset,  --keyfile-size,
              --readonly,   --test-passphrase,   --allow-discards,   --header,
              --key-slot, --master-key-file, --token-id, --token-only,  --dis-
              able-keyring, --disable-locks].

       luksSuspend <name>

              Suspends  an  active  device  (all  IO operations will block and
              accesses to the device will wait  indefinitely)  and  wipes  the
              encryption key from kernel memory. Needs kernel 2.6.19 or later.

              After this operation you have to use luksResume to reinstate the
              encryption key and unblock the device or  close  to  remove  the
              mapped device.

              WARNING: never suspend the device on which the cryptsetup binary
              resides.

              <options> can be [--header, --disable-locks].

       luksResume <name>

              Resumes a suspended device and reinstates  the  encryption  key.
              Prompts  interactively  for  a  passphrase  if --key-file is not
              given.

              <options> can be [--key-file, --keyfile-size,  --header,  --dis-
              able-keyring,--disable-locks]

       luksAddKey <device> [<key file with new key>]

              adds  a  new passphrase. An existing passphrase must be supplied
              interactively or via --key-file.  The new passphrase to be added
              can  be  specified  interactively or read from the file given as
              positional argument.

              <options> can be [--key-file, --keyfile-offset,  --keyfile-size,
              --new-keyfile-offset,   --new-keyfile-size,  --key-slot,  --mas-
              ter-key-file, --iter-time,  --force-password,  --header,  --dis-
              able-locks].

       luksRemoveKey <device> [<key file with passphrase to be removed>]

              Removes  the  supplied  passphrase  from  the  LUKS  device. The
              passphrase to be removed can be specified interactively, as  the
              positional argument or via --key-file.

              <options>  can be [--key-file, --keyfile-offset, --keyfile-size,
              --header, --disable-locks]

              WARNING: If you read the passphrase from stdin (without  further
              argument  or  with '-' as an argument to --key-file), batch-mode
              (-q) will be implicitly switched on and no warning will be given
              when  you  remove the last remaining passphrase from a LUKS con-
              tainer. Removing the last passphrase makes  the  LUKS  container
              permanently inaccessible.

       luksChangeKey <device> [<new key file>]

              Changes  an  existing  passphrase.  The passphrase to be changed
              must be supplied  interactively  or  via  --key-file.   The  new
              passphrase  can  be supplied interactively or in a file given as
              positional argument.

              If a key-slot is specified (via --key-slot), the passphrase  for
              that  key-slot  must  be given and the new passphrase will over-
              write the specified key-slot. If no key-slot  is  specified  and
              there  is still a free key-slot, then the new passphrase will be
              put into a free key-slot before the key-slot containing the  old
              passphrase  is  purged.  If  there is no free key-slot, then the
              key-slot with the old passphrase is overwritten directly.

              WARNING: If a key-slot is overwritten, a  media  failure  during
              this  operation  can  cause  the overwrite to fail after the old
              passphrase has been wiped and make the LUKS container inaccessi-
              ble.

              <options>  can be [--key-file, --keyfile-offset, --keyfile-size,
              --new-keyfile-offset,      --new-keyfile-size,       --key-slot,
              --force-password, --header, --disable-locks].

       luksKillSlot <device> <key slot number>

              Wipe the key-slot number <key slot> from the LUKS device. Except
              running in batch-mode (-q) a remaining passphrase must  be  sup-
              plied, either interactively or via --key-file.  This command can
              remove the last remaining key-slot, but requires an  interactive
              confirmation when doing so. Removing the last passphrase makes a
              LUKS container permanently inaccessible.

              <options> can be [--key-file, --keyfile-offset,  --keyfile-size,
              --header, --disable-locks].

              WARNING:  If you read the passphrase from stdin (without further
              argument or with '-' as an argument to  --key-file),  batch-mode
              (-q) will be implicitly switched on and no warning will be given
              when you remove the last remaining passphrase from a  LUKS  con-
              tainer.  Removing  the  last passphrase makes the LUKS container
              permanently inaccessible.

              NOTE: If there is no passphrase provided (on  stdin  or  through
              --key-file argument) and batch-mode (-q) is active, the key-slot
              is removed without any other warning.

       erase <device>
       luksErase <device>

              Erase all keyslots and make the LUKS container permanently inac-
              cessible.   You  do  not  need  to provide any password for this
              operation.

              WARNING: This operation is irreversible.

       luksUUID <device>

              Print the UUID of a LUKS device.
              Set new UUID if --uuid option is specified.

       isLuks <device>

              Returns true, if <device> is a  LUKS  device,  false  otherwise.
              Use  option -v to get human-readable feedback. 'Command success-
              ful.'  means the device is a LUKS device.

       luksDump <device>

              Dump the header information of a LUKS device.

              If the --dump-master-key option is used, the LUKS device  master
              key  is dumped instead of the keyslot info. Beware that the mas-
              ter key cannot be changed and can be used to  decrypt  the  data
              stored in the LUKS container without a passphrase and even with-
              out the LUKS header. This means that if the master key  is  com-
              promised,  the  whole device has to be erased to prevent further
              access. Use this option carefully.

              To dump the master key, a passphrase has to be supplied,  either
              interactively or via --key-file.

              <options>  can be [--dump-master-key, --key-file, --keyfile-off-
              set, --keyfile-size, --header, --disable-locks].

              WARNING: If --dump-master-key is used with  --key-file  and  the
              argument  to  --key-file  is '-', no validation question will be
              asked and no warning given.

       luksHeaderBackup <device> --header-backup-file <file>

              Stores a binary backup of the LUKS header and keyslot area.
              Note: Using '-' as filename writes the header backup to  a  file
              named '-'.

              WARNING:  This backup file and a passphrase valid at the time of
              backup allows decryption of the LUKS  data  area,  even  if  the
              passphrase  was  later  changed or removed from the LUKS device.
              Also note that with a header backup  you  lose  the  ability  to
              securely wipe the LUKS device by just overwriting the header and
              key-slots. You either need to securely erase all header  backups
              in  addition  or overwrite the encrypted data area as well.  The
              second option is less secure, as some sectors can survive,  e.g.
              due to defect management.

       luksHeaderRestore <device> --header-backup-file <file>

              Restores  a  binary  backup  of the LUKS header and keyslot area
              from the specified file.
              Note: Using '-' as filename reads the header backup from a  file
              named '-'.

              WARNING:   Header  and  keyslots  will  be  replaced,  only  the
              passphrases from the backup will work afterward.

              This command requires that the master key size and  data  offset
              of  the  LUKS  header  already  on  the device and of the header
              backup match. Alternatively, if there is no LUKS header  on  the
              device, the backup will also be written to it.

       token <add|remove> <device>

              Adds  a  new  keyring  token  to  enable  auto-activation of the
              device.  For the auto-activation, the passphrase must be  stored
              in   keyring   with  the  specified  description.  Usually,  the
              passphrase should be stored in  user  or  user-session  keyring.
              The token command is supported only for LUKS2.

              For adding new keyring token, option --key-description is manda-
              tory.  Also, new token is assigned to key  slot  specified  with
              --key-slot  option  or  to  all  active  key  slots  in the case
              --key-slot option is omitted.

              To remove existing token, specify the token ID which  should  be
              removed with --token-id option.

              WARNING:  The  action  token  remove removes any token type, not
              just keyring  type  from  token  slot  specified  by  --token-id
              option.

              <options>    can    be    [--header,   --token-id,   --key-slot,
              --key-description, --disable-locks, --disable-keyring].

       convert <device> --type <format>

              Converts the device between LUKS and LUKS2 format (if possible).
              The  conversion  will not be performed if there is an additional
              LUKS2 feature or LUKS has unsupported header size.

              WARNING: The convert action can destroy the LUKS header  in  the
              case  of  a  crash during conversion or if a media error occurs.
              Always create a header backup before performing this operation!

              <options> can be [--header, --type].

       config <device>

              Set permanent configuration options (store to LUKS header).  The
              config command is supported only for LUKS2.

              The permanent options can be --priority to set priority (normal,
              prefer, ignore) for keyslot (specified by --key-slot) or --label
              and --subsystem.

              <options>  can be [--priority, --label, --subsystem, --key-slot,
              --header].

loop-AES EXTENSION
       cryptsetup supports mapping loop-AES encrypted partition using  a  com-
       patibility mode.

       open --type loopaes <device> <name> --key-file <keyfile>
       loopaesOpen <device> <name> --key-file <keyfile>  (old syntax)

              Opens the loop-AES <device> and sets up a mapping <name>.

              If  the  key  file is encrypted with GnuPG, then you have to use
              --key-file=- and decrypt it before use, e.g. like this:
              gpg --decrypt <keyfile> |  cryptsetup  loopaesOpen  --key-file=-
              <device> <name>

              WARNING:  The  loop-AES extension cannot use the direct input of
              key file on real terminal because the keys are separated by end-
              of-line and only part of the multi-key file would be read.
              If you need it in script, just use the pipe redirection:
              echo  $keyfile  |  cryptsetup  loopaesOpen --key-file=- <device>
              <name>

              Use --keyfile-size to specify the proper key length if needed.

              Use --offset to specify device offset. Note that the units  need
              to be specified in number of 512 byte sectors.

              Use --skip to specify the IV offset. If the original device used
              an offset and but did not use it in IV sector calculations,  you
              have to explicitly use --skip 0 in addition to the offset param-
              eter.

              Use --hash to override the default hash function for  passphrase
              hashing (otherwise it is detected according to key size).

              <options>  can  be  [--key-file,  --key-size,  --offset, --skip,
              --hash, --readonly, --allow-discards].

       See also section 7 of the FAQ and  http://loop-aes.sourceforge.net  for
       more information regarding loop-AES.

TCRYPT (TrueCrypt-compatible and VeraCrypt) EXTENSION
       cryptsetup  supports  mapping  of  TrueCrypt, tcplay or VeraCrypt (with
       --veracrypt option) encrypted partition using  a  native  Linux  kernel
       API.   Header  formatting  and  TCRYPT  header change is not supported,
       cryptsetup never changes TCRYPT header on-device.

       TCRYPT extension requires kernel userspace crypto API to  be  available
       (introduced  in  Linux  kernel  2.6.38).  If you are configuring kernel
       yourself, enable "User-space interface for symmetric key  cipher  algo-
       rithms"  in "Cryptographic API" section (CRYPTO_USER_API_SKCIPHER .con-
       fig option).

       Because TCRYPT header is encrypted, you have to  always  provide  valid
       passphrase and keyfiles.

       Cryptsetup  should  recognize all header variants, except legacy cipher
       chains using LRW encryption mode with 64 bits encryption block  (namely
       Blowfish  in  LRW  mode is not recognized, this is limitation of kernel
       crypto API).

       To recognize a VeraCrypt device use the --veracrypt option.   VeraCrypt
       is just extension of TrueCrypt header with increased iteration count so
       unlocking can take quite a lot  of  time  (in  comparison  with  TCRYPT
       device).

       To  open a VeraCrypt device with a custom Personal Iteration Multiplier
       (PIM)  value,  additionally  to  --veracrypt   use  either  the  --ver-
       acrypt-pim=<PIM>  option  to  directly  specify the PIM on the command-
       line or use --veracrypt-query-pim to be prompted for the PIM.

       The PIM value affects the  number  of  iterations  applied  during  key
       derivation.    Please    refer    to   https://www.veracrypt.fr/en/Per-
       sonal%20Iterations%20Multiplier%20(PIM).html for more detailed informa-
       tion.

       NOTE:  Activation  with  tcryptOpen is supported only for cipher chains
       using LRW or XTS encryption modes.

       The tcryptDump command should work for all  recognized  TCRYPT  devices
       and doesn't require superuser privilege.

       To map system device (device with boot loader where the whole encrypted
       system resides) use --tcrypt-system  option.   You  can  use  partition
       device  as  the parameter (parameter must be real partition device, not
       an image in a file), then only this partition is mapped.

       If you have the whole TCRYPT device as a file image and you want to map
       multiple  partition  encrypted  with  system  encryption, please create
       loopback mapping with partitions first (losetup -P, see losetup(8)  man
       page for more info), and use loop partition as the device parameter.

       If  you  use  the  whole base device as a parameter, one device for the
       whole system encryption is mapped. This  mode  is  available  only  for
       backward  compatibility  with  older  cryptsetup  versions which mapped
       TCRYPT system encryption using the whole device.

       To use hidden  header  (and  map  hidden  device,  if  available),  use
       --tcrypt-hidden option.

       To  explicitly  use  backup  (secondary)  header,  use  --tcrypt-backup
       option.

       NOTE: There is no protection for a hidden volume if the outer volume is
       mounted.  The  reason  is  that  if there were any protection, it would
       require some metadata describing what to protect in  the  outer  volume
       and the hidden volume would become detectable.

       open --type tcrypt <device> <name>
       tcryptOpen <device> <name>  (old syntax)

              Opens the TCRYPT (a TrueCrypt-compatible) <device> and sets up a
              mapping <name>.

              <options> can be [--key-file, --tcrypt-hidden,  --tcrypt-system,
              --tcrypt-backup,   --readonly,  --test-passphrase,  --allow-dis-
              cards, --veracrypt, --veracrypt-pim, --veracrypt-query-pim].

              The keyfile parameter allows a combination of file content  with
              the  passphrase and can be repeated. Note that using keyfiles is
              compatible with TCRYPT and is different from LUKS keyfile logic.

              WARNING: Option --allow-discards cannot be combined with  option
              --tcrypt-hidden.  For  normal mapping, it can cause the destruc-
              tion of hidden volume (hidden volume appears as unused space for
              outer volume so this space can be discarded).

       tcryptDump <device>

              Dump the header information of a TCRYPT device.

              If  the --dump-master-key option is used, the TCRYPT device mas-
              ter key is dumped instead of TCRYPT header info. Beware that the
              master key (or concatenated master keys if cipher chain is used)
              can be used to decrypt the data stored in the  TCRYPT  container
              without a passphrase.  This means that if the master key is com-
              promised, the whole device has to be erased to  prevent  further
              access. Use this option carefully.

              <options>  can  be [--dump-master-key, --key-file, --tcrypt-hid-
              den, --tcrypt-system, --tcrypt-backup].

              The keyfile parameter allows a combination of file content  with
              the passphrase and can be repeated.

       See  also  https://en.wikipedia.org/wiki/TrueCrypt for more information
       regarding TrueCrypt.

       Please note that cryptsetup does not use TrueCrypt code, please  report
       all  problems related to this compatibility extension to the cryptsetup
       project.

MISCELLANEOUS
       repair <device>

              Tries to repair the device metadata if possible. Currently  sup-
              ported only for LUKS device type.

              This  command  is  useful to fix some known benign LUKS metadata
              header corruptions. Only basic corruptions of unused keyslot are
              fixable.  This command will only change the LUKS header, not any
              key-slot data.

              WARNING: Always create a binary backup of  the  original  header
              before calling this command.

       benchmark <options>

              Benchmarks  ciphers  and KDF (key derivation function).  Without
              parameters, it tries to measure few common configurations.

              To benchmark  other  ciphers  or  modes,  you  need  to  specify
              --cipher and --key-size options or --hash for KDF test.

              NOTE:  This  benchmark is using memory only and is only informa-
              tive.  You cannot directly predict real storage encryption speed
              from it.

              For  testing  block  ciphers,  this  benchmark  requires  kernel
              userspace crypto API to be available (introduced in Linux kernel
              2.6.38).   If you are configuring kernel yourself, enable "User-
              space interface for symmetric key cipher algorithms" in "Crypto-
              graphic API" section (CRYPTO_USER_API_SKCIPHER .config option).

              <options> can be [--cipher, --key-size, --hash].

OPTIONS
       --verbose, -v
              Print more information on command execution.

       --debug
              Run  in debug mode with full diagnostic logs. Debug output lines
              are always prefixed by '#'.

       --type <device-type>
              Specifies required device type, for more info  read  BASIC  COM-
              MANDS section.

       --hash, -h <hash-spec>
              Specifies  the  passphrase  hash for open (for plain and loopaes
              device types).

              Specifies the hash used in the LUKS key setup scheme and  volume
              key  digest  for luksFormat. The specified hash is used as hash-
              parameter for PBKDF2 and for the AF splitter.

              The specified hash name is  passed  to  the  compiled-in  crypto
              backend.   Different backends may support different hashes.  For
              luksFormat, the hash algorithm must provide at least 160 bits of
              output,  which excludes, e.g., MD5. Do not use a non-crypto hash
              like "crc32" as this breaks security.

              Values compatible with old version of cryptsetup are "ripemd160"
              for open --type plain and "sha1" for luksFormat.

              Use cryptsetup --help to show the defaults.

       --cipher, -c <cipher-spec>
              Set the cipher specification string.

              cryptsetup  --help  shows the compiled-in defaults.  The current
              default in the distributed sources is "aes-cbc-essiv:sha256" for
              plain dm-crypt and "aes-xts-plain64" for LUKS.

              If  a  hash is part of the cipher specification, then it is used
              as part of the IV generation. For example, ESSIV  needs  a  hash
              function, while "plain64" does not and hence none is specified.

              For  XTS mode you can optionally set a key size of 512 bits with
              the -s option. Key size for XTS mode is  twice  that  for  other
              modes for the same security level.

              XTS  mode  requires  kernel 2.6.24 or later and plain64 requires
              kernel 2.6.33 or later. More information can  be  found  in  the
              FAQ.

       --verify-passphrase, -y
              When interactively asking for a passphrase, ask for it twice and
              complain if both inputs do not match. Advised  when  creating  a
              regular  mapping for the first time, or when running luksFormat.
              Ignored on input from file or stdin.

       --key-file, -d name
              Read the passphrase from file.

              If the name given is "-", then the passphrase will be read  from
              stdin.   In  this case, reading will not stop at newline charac-
              ters.

              With LUKS, passphrases supplied via --key-file  are  always  the
              existing  passphrases requested by a command, except in the case
              of luksFormat where --key-file is equivalent to  the  positional
              key file argument.

              If  you  want  to set a new passphrase via key file, you have to
              use a positional argument to luksAddKey.

              See section NOTES ON PASSPHRASE PROCESSING for more information.

       --keyfile-offset value
              Skip value bytes at the beginning of the key file.   Works  with
              all commands that accept key files.

       --keyfile-size, -l value
              Read a maximum of value bytes from the key file.  The default is
              to read the whole file up to the compiled-in maximum that can be
              queried  with  --help.  Supplying more data than the compiled-in
              maximum aborts the operation.

              This option is useful to cut trailing newlines, for example.  If
              --keyfile-offset  is also given, the size count starts after the
              offset.  Works with all commands that accept key files.

       --new-keyfile-offset value
              Skip value bytes at the start when adding a new passphrase  from
              key file with luksAddKey.

       --new-keyfile-size  value
              Read  a maximum of value bytes when adding a new passphrase from
              key file with luksAddKey.  The default is to read the whole file
              up  to  the  compiled-in maximum length that can be queried with
              --help.  Supplying more than the compiled in maximum aborts  the
              operation.   When  --new-keyfile-offset  is  also given, reading
              starts after the offset.

       --master-key-file
              Use a master key stored in a file.

              For luksFormat this allows creating a LUKS header with this spe-
              cific  master  key. If the master key was taken from an existing
              LUKS header and all other parameters are the same, then the  new
              header  decrypts  the  data encrypted with the header the master
              key was taken from.

              WARNING: If you create your own master key,  you  need  to  make
              sure  to  do  it  right.  Otherwise,  you can end up with a low-
              entropy or otherwise partially predictable master key which will
              compromise security.

              For  luksAddKey this allows adding a new passphrase without hav-
              ing to know an existing one.

              For open this allows one to open the LUKS device without  giving
              a passphrase.

       --dump-master-key
              For  luksDump  this  option  includes the master key in the dis-
              played information. Use with care, as the master key can be used
              to bypass the passphrases, see also option --master-key-file.

       --use-random

       --use-urandom
              For  luksFormat  these options define which kernel random number
              generator will be used to create the  master  key  (which  is  a
              long-term key).

              See  NOTES ON RANDOM NUMBER GENERATORS for more information. Use
              cryptsetup --help to show the compiled-in default random  number
              generator.

              WARNING:  In  a  low-entropy situation (e.g. in an embedded sys-
              tem), both selections are problematic.  Using  /dev/urandom  can
              lead  to  weak  keys.   Using /dev/random can block a long time,
              potentially forever, if not enough entropy can be  harvested  by
              the kernel.

       --key-slot, -S <0-7>
              For  LUKS  operations that add key material, this options allows
              you to specify which key slot is selected for the new key.  This
              option can be used for luksFormat, and luksAddKey.
              In  addition,  for open, this option selects a specific key-slot
              to compare the passphrase  against.   If  the  given  passphrase
              would only match a different key-slot, the operation fails.

       --key-size, -s <bits>
              Sets  key  size in bits. The argument has to be a multiple of 8.
              The possible key-sizes are limited by the cipher and mode used.

              See /proc/crypto for more information.  Note  that  key-size  in
              /proc/crypto is stated in bytes.

              This  option  can  be  used for open --type plain or luksFormat.
              All other LUKS actions will use the key-size  specified  in  the
              LUKS  header.   Use  cryptsetup  --help  to show the compiled-in
              defaults.

       --size, -b <number of 512 byte sectors>
              Set the size of the device in sectors of 512 bytes.  This option
              is only relevant for the open and resize actions.

       --offset, -o <number of 512 byte sectors>
              Start  offset  in  the backend device in 512-byte sectors.  This
              option is only relevant  for  the  open  action  with  plain  or
              loopaes device types.

       --skip, -p <number of 512 byte sectors>
              Start  offset  used  in  IV calculation in 512-byte sectors (how
              many sectors of the encrypted data to skip  at  the  beginning).
              This  option  is only relevant for the open action with plain or
              loopaes device types.

              Hence, if --offset n, and --skip s, sector n (the  first  sector
              of  the  encrypted device) will get a sector number of s for the
              IV calculation.

       --readonly, -r
              set up a read-only mapping.

       --shared
              Creates an additional mapping for one common ciphertext  device.
              Arbitrary  mappings are supported.  This option is only relevant
              for the open --type  plain  action.  Use  --offset,  --size  and
              --skip to specify the mapped area.

       --pbkdf <PBKDF spec>
              Set Password-Based Key Derivation Function (PBKDF) algorithm for
              LUKS keyslot.  The PBKDF can be: pbkdf2 (for PBKDF2 according to
              RFC2898),  argon2i  for  Argon2i  or  argon2id for Argon2id (see
              https://www.cryptolux.org/index.php/Argon2 for more info).

              For LUKS1, only PBKDF2 is accepted (no need to use this option).
              The  default PBKDF2 for LUKS2 is set during compilation time and
              is available in cryptsetup --help output.

              A PBKDF is used for increasing dictionary and brute-force attack
              cost  for  keyslot passwords. The parameters can be time, memory
              and parallel cost.

              For PBKDF2, only time cost (number of iterations) applies.   For
              Argon2i/id,  there  is  also memory cost (memory required during
              the process of key derivation)  and  parallel  cost  (number  of
              threads that run in parallel during the key derivation.

              Note  that  increasing  memory  cost also increases time, so the
              final parameter values are measured by a benchmark.  The  bench-
              mark  tries  to  find iteration time (--iter-time) with required
              memory cost --pbkdf-memory. If it is not  possible,  the  memory
              cost  is  decreased as well.  The parallel cost --pbkdf-parallel
              is constant, is is checked against available CPU cores  (if  not
              available, it is decreased) and the maximum parallel cost is 4.

              You  can  see  all PBKDF parameters for particular LUKS2 keyslot
              with luksDump command.

              NOTE: If you do not want to use benchmark and  want  to  specify
              all   parameters  directly,  use  --pbkdf-force-iterations  with
              --pbkdf-memory and --pbkdf-parallel.   This  will  override  the
              values  without  benchmarking.  Note it can cause extremely long
              unlocking time. Use only is specified cases, for example, if you
              know that the formatted device will be used on some small embed-
              ded system.  In this case, the LUKS PBKDF2 digest will be set to
              the minimum iteration count.

       --iter-time, -i <number of milliseconds>
              The  number  of milliseconds to spend with PBKDF passphrase pro-
              cessing.  This option is only relevant for LUKS operations  that
              set  or  change  passphrases,  such as luksFormat or luksAddKey.
              Specifying 0 as parameter selects the compiled-in default.

       --pbkdf-memory <number>
              Set the memory cost for PBKDF (for Argon2i/id the number  repre-
              sents  kilobytes).   Note that it is maximal value, PBKDF bench-
              mark or available physical memory can decrease it.  This  option
              is not available for PBKDF2.

       --pbkdf-parallel <number>
              Set  the  parallel  cost for PBKDF (number of threads, up to 4).
              Note that it is maximal value, it is decreased automatically  if
              CPU  online  count  is  lower.  This option is not available for
              PBKDF2.

       --pbkdf-force-iterations <num>
              Avoid PBKDF benchmark and set time cost  (iterations)  directly.
              It  can  be used for LUKS/LUKS2 device only.  See --pbkdf option
              for more info.

       --batch-mode, -q
              Suppresses all confirmation questions. Use with care!

              If the -y option is not specified, this option also switches off
              the passphrase verification for luksFormat.

       --progress-frequency <seconds>
              Print separate line every <seconds> with wipe progress.

       --timeout, -t <number of seconds>
              The number of seconds to wait before timeout on passphrase input
              via terminal. It is relevant every time a passphrase  is  asked,
              for  example  for  open,  luksFormat  or  luksAddKey.  It has no
              effect if used in conjunction with --key-file.
              This option is useful when the system should not  stall  if  the
              user  does not input a passphrase, e.g. during boot. The default
              is a value of 0 seconds, which means to wait forever.

       --tries, -T
              How often the input of the passphrase shall  be  retried.   This
              option is relevant every time a passphrase is asked, for example
              for open, luksFormat or luksAddKey.  The default is 3 tries.

       --align-payload <number of 512 byte sectors>
              Align payload at a boundary of  value  512-byte  sectors.   This
              option is relevant for luksFormat.

              If not specified, cryptsetup tries to use the topology info pro-
              vided by the kernel for the underlying device to get the optimal
              alignment.   If not available (or the calculated value is a mul-
              tiple of the default) data is  by  default  aligned  to  a  1MiB
              boundary (i.e. 2048 512-byte sectors).

              For  a detached LUKS header, this option specifies the offset on
              the data device. See also the --header option.

       --uuid=UUID
              Use the provided UUID for the luksFormat command instead of gen-
              erating  a new one. Changes the existing UUID when used with the
              luksUUID command.

              The UUID must be provided in  the  standard  UUID  format,  e.g.
              12345678-1234-1234-1234-123456789abc.

       --allow-discards
              Allow  the  use of discard (TRIM) requests for the device.  This
              option is only relevant for open action.

              WARNING: This  command  can  have  a  negative  security  impact
              because  it  can make filesystem-level operations visible on the
              physical device. For  example,  information  leaking  filesystem
              type,  used  space,  etc.  may  be extractable from the physical
              device if the discarded blocks  can  be  located  later.  If  in
              doubt, do not use it.

              A kernel version of 3.1 or later is needed. For earlier kernels,
              this option is ignored.

       --perf-same_cpu_crypt
              Perform encryption using the same cpu that IO was submitted  on.
              The  default  is  to use an unbound workqueue so that encryption
              work is automatically balanced  between  available  CPUs.   This
              option is only relevant for open action.

              NOTE:  This option is available only for low-level dm-crypt per-
              formance tuning, use only if you need a change  to  default  dm-
              crypt behaviour. Needs kernel 4.0 or later.

       --perf-submit_from_crypt_cpus
              Disable offloading writes to a separate thread after encryption.
              There are some situations where offloading write bios  from  the
              encryption  threads to a single thread degrades performance sig-
              nificantly.  The default is to offload write bios  to  the  same
              thread.  This option is only relevant for open action.

              NOTE:  This option is available only for low-level dm-crypt per-
              formance tuning, use only if you need a change  to  default  dm-
              crypt behaviour. Needs kernel 4.0 or later.

       --test-passphrase
              Do not activate the device, just verify passphrase.  This option
              is only relevant for open action (the device mapping name is not
              mandatory if this option is used).

       --header <device or file storing the LUKS header>
              Use  a  detached  (separated)  metadata device or file where the
              LUKS header is stored. This option allows one to  store  cipher-
              text and LUKS header on different devices.

              This  option  is  only relevant for LUKS devices and can be used
              with the luksFormat, open, luksSuspend, luksResume,  status  and
              resize commands.

              For luksFormat with a file name as the argument to --header, the
              file will be automatically created if it does  not  exist.   See
              the cryptsetup FAQ for header size calculation.

              For  other  commands  that change the LUKS header (e.g. luksAdd-
              Key), specify the device or file with the LUKS  header  directly
              as the LUKS device.

              If  used with luksFormat, the --align-payload option is taken as
              absolute sector alignment on ciphertext device and can be zero.

              WARNING: There is no check whether the ciphertext device  speci-
              fied  actually  belongs  to  the  header given. In fact, you can
              specify an arbitrary device as the ciphertext  device  for  open
              with the --header option. Use with care.

       --header-backup-file <file>
              Specify  file  with  header  backup for luksHeaderBackup or luk-
              sHeaderBackup actions.

       --force-password
              Do not use password quality checking for new LUKS passwords.

              This  option  applies  only  to   luksFormat,   luksAddKey   and
              luksChangeKey  and  is  ignored  if  cryptsetup is built without
              password quality checking support.

              For more info about password quality check, see the manual  page
              for pwquality.conf(5) and passwdqc.conf(5).

       --deferred
              Defers  device  removal  in  close  command  until the last user
              closes it.

       --disable-locks
              Disable lock protection for metadata on disk.   This  option  is
              valid only for LUKS2 and ignored for other formats.

              WARNING:  Do  not use this option unless you run cryptsetup in a
              restricted environment where locking is  impossible  to  perform
              (where /run directory cannot be used).

       --disable-keyring
              Do  not  load  volume  key  in  kernel keyring but use store key
              directly in the dm-crypt target.  This option is supported  only
              for the LUKS2 format.

       --key-description <text>
              Set key description in keyring for use with token command.

       --priority <normal|prefer|ignore>
              Set  a  priority  for LUKS2 keyslot.  The prefer priority marked
              slots are tried before normal priority.   The  ignored  priority
              means,  that  slot is never used, if not explicitly requested by
              --key-slot option.

       --token-id
              Specify what token to use in actions token, open or resize.   If
              omitted,  all available tokens will be checked before proceeding
              further with passphrase prompt.

       --token-only
              Do not proceed further  with  action  (any  of  token,  open  or
              resize)  if  token activation failed. Without the option, action
              asks for passphrase to proceed further.

       --sector-size <bytes>
              Set sector size for use with disk encryption. It must  be  power
              of  two  and in range 512 - 4096 bytes. The default is 512 bytes
              sectors.  This option is available only in the LUKS2 mode.

              Note that if sector size is higher than underlying device  hard-
              ware sector and there is not integrity protection that uses data
              journal, using this option can increase risk on incomplete  sec-
              tor writes during a power fail.

              If  used together with --integrity option and dm-integrity jour-
              nal, the atomicity of writes is guaranteed in all cases (but  it
              cost write performance - data has to be written twice).

              Increasing  sector size from 512 bytes to 4096 bytes can provide
              better performance on most of the  modern  storage  devices  and
              also with some hw encryption accelerators.

       --persistent
              If  used  with  LUKS2 devices and activation commands like open,
              the specified activation flags  are  persistently  written  into
              metadata  and used next time automatically even for normal acti-
              vation.  (No need to use cryptab or other  system  configuration
              files.)      Only    --allow-discards,    --perf-same_cpu_crypt,
              --perf-submit_from_crypt_cpus and --integrity-no-journal can  be
              stored persistently.

       --label <LABEL>
              --subsystem  <SUBSYSTEM> Set label and subsystem description for
              LUKS2 device, can be used in config  and  format  actions.   The
              label and subsystem are optional fields and can be later used in
              udev scripts for triggering user actions once device  marked  by
              these labels is detected.

       --integrity <integrity algorithm>
              Specify  integrity  algorithm  to be used for authenticated disk
              encryption in LUKS2.

              WARNING:  This  extension  is  EXPERIMENTAL  and  requires   dm-
              integrity  kernel  target (available since kernel version 4.12).
              For more info, see AUTHENTICATED DISK ENCRYPTION section.

       --integrity-no-journal
              Activate device with integrity  protection  without  using  data
              journal  (direct  write  of data and integrity tags).  Note that
              without journal power fail can cause non-atomic write  and  data
              corruption.  Use only if journalling is performed on a different
              storage layer.

       --integrity-no-wipe
              Skip wiping of device authentication (integrity)  tags.  If  you
              skip  this step, sectors will report invalid integrity tag until
              an application write to the sector.

              NOTE: Even some writes to the device can fail if  the  write  is
              not aligned to page size and page-cache initiates read of a sec-
              tor with invalid integrity tag.

       --tcrypt-hidden
              --tcrypt-system --tcrypt-backup Specify which TrueCrypt  on-disk
              header  will be used to open the device.  See TCRYPT section for
              more info.

       --veracrypt
              Allow VeraCrypt compatible mode. Only for TCRYPT extension.  See
              TCRYPT section for more info.

       --veracrypt-pim
              --veracrypt-query-pim Use a custom Personal Iteration Multiplier
              (PIM) for VeraCrypt device.  See TCRYPT section for more info.

       --version
              Show the program version.

       --usage
              Show short option help.

       --help, -?
              Show help text and default parameters.

RETURN CODES
       Cryptsetup returns 0 on success and a non-zero value on error.

       Error codes are: 1 wrong parameters, 2 no permission (bad  passphrase),
       3  out  of memory, 4 wrong device specified, 5 device already exists or
       device is busy.

NOTES ON PASSPHRASE PROCESSING FOR PLAIN MODE
       Note that no iterated hashing or salting is done  in  plain  mode.   If
       hashing  is  done,  it  is  a  single direct hash. This means that low-
       entropy passphrases are easy to attack in plain mode.

       From a terminal: The passphrase is read until the first  newline,  i.e.
       '\n'.   The  input  without the newline character is processed with the
       default hash or the hash specified with --hash.  The hash  result  will
       be  truncated to the key size of the used cipher, or the size specified
       with -s.

       From stdin: Reading will continue until a newline (or until the maximum
       input size is reached), with the trailing newline stripped. The maximum
       input size is defined by the same compiled-in default as for the  maxi-
       mum key file size and can be overwritten using --keyfile-size option.

       The  data  read will be hashed with the default hash or the hash speci-
       fied with --hash.  The hash result will be truncated to the key size of
       the used cipher, or the size specified with -s.

       Note  that  if  --key-file=-  is  used  for reading the key from stdin,
       trailing newlines are not stripped from the input.

       If "plain" is used as argument to --hash, the input data  will  not  be
       hashed.  Instead, it will be zero padded (if shorter than the key size)
       or truncated (if longer than the key size) and  used  directly  as  the
       binary  key.  This  is useful for directly specifying a binary key.  No
       warning will be given if the amount of data read  from  stdin  is  less
       than the key size.

       From  a  key  file:  It  will  be truncated to the key size of the used
       cipher or the size given by -s and directly used as a binary key.

       WARNING: The --hash argument is being ignored.  The  --hash  option  is
       usable only for stdin input in plain mode.

       If  the  key file is shorter than the key, cryptsetup will quit with an
       error.  The maximum input size  is  defined  by  the  same  compiled-in
       default  as  for the maximum key file size and can be overwritten using
       --keyfile-size option.

NOTES ON PASSPHRASE PROCESSING FOR LUKS
       LUKS uses PBKDF2 to protect against dictionary attacks and to give some
       protection  to low-entropy passphrases (see RFC 2898 and the cryptsetup
       FAQ).

       From a terminal: The passphrase is read until  the  first  newline  and
       then processed by PBKDF2 without the newline character.

       From  stdin: LUKS will read passphrases from stdin up to the first new-
       line character or the compiled-in maximum key file  length.  If  --key-
       file-size is given, it is ignored.

       From key file: The complete keyfile is read up to the compiled-in maxi-
       mum size. Newline characters do not terminate  the  input.  The  --key-
       file-size option can be used to limit what is read.

       Passphrase  processing: Whenever a passphrase is added to a LUKS header
       (luksAddKey, luksFormat), the user may specify how much  the  time  the
       passphrase processing should consume. The time is used to determine the
       iteration count for PBKDF2 and higher times will offer  better  protec-
       tion  for  low-entropy  passphrases,  but open will take longer to com-
       plete. For passphrases that have  entropy  higher  than  the  used  key
       length, higher iteration times will not increase security.

       The  default setting of one or two seconds is sufficient for most prac-
       tical cases. The only exception is a low-entropy passphrase used  on  a
       device  with  a slow CPU, as this will result in a low iteration count.
       On a slow device, it may be advisable to increase  the  iteration  time
       using  the  --iter-time  option  in  order to obtain a higher iteration
       count. This does slow down all later luksOpen operations accordingly.

INCOHERENT BEHAVIOR FOR INVALID PASSPHRASES/KEYS
       LUKS checks for a valid  passphrase  when  an  encrypted  partition  is
       unlocked.  The behavior of plain dm-crypt is different.  It will always
       decrypt with the passphrase given. If the given  passphrase  is  wrong,
       the  device  mapped  by  plain  dm-crypt will essentially still contain
       encrypted data and will be unreadable.

NOTES ON SUPPORTED CIPHERS, MODES, HASHES AND KEY SIZES
       The available combinations of ciphers,  modes,  hashes  and  key  sizes
       depend  on  kernel  support.  See  /proc/crypto for a list of available
       options. You might need to load additional  kernel  crypto  modules  in
       order to get more options.

       For  the  --hash  option,  if the crypto backend is libgcrypt, then all
       algorithms supported by the gcrypt library are  available.   For  other
       crypto backends, some algorithms may be missing.

NOTES ON PASSPHRASES
       Mathematics  can't be bribed. Make sure you keep your passphrases safe.
       There are a few nice tricks for constructing a fallback, when  suddenly
       out of the blue, your brain refuses to cooperate.  These fallbacks need
       LUKS, as it's only possible with LUKS  to  have  multiple  passphrases.
       Still,  if  your  attacker  model  does  not  prevent  it, storing your
       passphrase in a sealed envelope somewhere may be a good idea as well.

NOTES ON RANDOM NUMBER GENERATORS
       Random Number Generators (RNG) used in cryptsetup are always the kernel
       RNGs without any modifications or additions to data stream produced.

       There  are  two  types  of  randomness  cryptsetup/LUKS needs. One type
       (which always uses /dev/urandom) is used for salts, the AF splitter and
       for wiping deleted keyslots.

       The  second  type  is  used for the volume (master) key. You can switch
       between using /dev/random and /dev/urandom  here, see --use-random  and
       --use-urandom  options.  Using  /dev/random  on a system without enough
       entropy sources can cause  luksFormat  to  block  until  the  requested
       amount of random data is gathered. In a low-entropy situation (embedded
       system), this can take a very long time and potentially forever. At the
       same  time,  using /dev/urandom in a low-entropy situation will produce
       low-quality keys. This is a serious problem, but solving it is  out  of
       scope for a mere man-page.  See urandom(4) for more information.

AUTHENTICATED DISK ENCRYPTION (EXPERIMENTAL)
       Since  Linux  kernel  version 4.12 dm-crypt supports authenticated disk
       encryption.

       Normal disk encryption modes are length-preserving (plaintext sector is
       of the same size as a ciphertext sector) and can provide only confiden-
       tiality protection, but not cryptographically sound data integrity pro-
       tection.

       Authenticated modes require additional space per-sector for authentica-
       tion tag and use Authenticated Encryption with Additional  Data  (AEAD)
       algorithms.

       If  you  configure  LUKS2  device with data integrity protection, there
       will be an underlying dm-integrity device,  which  provides  additional
       per-sector  metadata  space and also provide data journal protection to
       ensure atomicity of data and metadata update.  Because  there  must  be
       additional  space for metadata and journal, the available space for the
       device will be smaller than for length-preserving modes.

       The dm-crypt device then resides on top of such a dm-integrity  device.
       All  activation  and  deactivation of this device stack is performed by
       cryptsetup, there is no difference in using luksOpen for integrity pro-
       tected devices.  If you want to format LUKS2 device with data integrity
       protection, use --integrity option.

       Some integrity modes requires two independent keys (key for  encryption
       and  for  authentication).  Both  these  keys  are  stored  in one LUKS
       keyslot.

       WARNING: All support for authenticated modes is experimental and  there
       are  only  some modes available for now. Note that there are a very few
       authenticated encryption algorithms that are suitable for disk  encryp-
       tion.

NOTES ON LOOPBACK DEVICE USE
       Cryptsetup  is  usually used directly on a block device (disk partition
       or LVM volume). However, if the device argument is a  file,  cryptsetup
       tries  to  allocate  a  loopback device and map it into this file. This
       mode requires Linux kernel 2.6.25 or more  recent  which  supports  the
       loop autoclear flag (loop device is cleared on the last close automati-
       cally). Of course, you can always map a file to a loop-device manually.
       See the cryptsetup FAQ for an example.

       When device mapping is active, you can see the loop backing file in the
       status command output. Also see losetup(8).

LUKS2 header locking
       The LUKS2 on-disk metadata is updated in several steps and  to  achieve
       proper  atomic  update,  there is a locking mechanism.  For an image in
       file, code uses flock(2) system call.  For a block device, lock is per-
       formed  over  a  special file stored in a locking directory (by default
       /run/lock/cryptsetup).  The locking directory should  be  created  with
       the  proper  security  context  by  the distribution during the boot-up
       phase.  Only LUKS2 uses locks, other formats do not use this mechanism.

DEPRECATED ACTIONS
       The reload action is no longer supported.  Please use dmsetup(8) if you
       need to directly manipulate with the device mapping table.

       The luksDelKey was replaced with luksKillSlot.

REPORTING BUGS
       Report  bugs,  including  ones  in the documentation, on the cryptsetup
       mailing list at <dm-crypt@saout.de> or in the 'Issues' section on  LUKS
       website.   Please  attach  the  output  of  the failed command with the
       --debug option added.

AUTHORS
       cryptsetup originally written by Jana Saout <jana@saout.de>
       The LUKS extensions and original man page were written by Clemens Fruh-
       wirth <clemens@endorphin.org>.
       Man page extensions by Milan Broz <gmazyland@gmail.com>.
       Man page rewrite and extension by Arno Wagner <arno@wagner.name>.

COPYRIGHT
       Copyright (C) 2004 Jana Saout
       Copyright (C) 2004-2006 Clemens Fruhwirth
       Copyright (C) 2009-2018 Red Hat, Inc.
       Copyright (C) 2009-2018 Milan Broz
       Copyright (C) 2012-2014 Arno Wagner

       This is free software; see the source for copying conditions.  There is
       NO warranty; not even for MERCHANTABILITY or FITNESS FOR  A  PARTICULAR
       PURPOSE.

SEE ALSO
       The LUKS website at https://gitlab.com/cryptsetup/cryptsetup/

       The cryptsetup FAQ, contained in the distribution package and online at
       https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions

       The cryptsetup mailing list and list archive, see FAQ entry 1.6.

       The  LUKS  on-disk  format  specification  available  at   https://git-
       lab.com/cryptsetup/cryptsetup/wikis/Specification

cryptsetup                       January 2018                    CRYPTSETUP(8)
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