[Bug 1875885] Re: luks cannot create small volumes < 8M

[francis cagney]

Here is my "df -h" after mounting an 800M old volume, and the one
created on 16.04 4.7M just now

Filesystem         Size  Used Avail Use% Mounted on
udev               3.8G     0  3.8G   0% /dev
tmpfs              785M  2.2M  783M   1% /run
/dev/sda8           46G   17G   27G  38% /
tmpfs              3.9G   26M  3.9G   1% /dev/shm
tmpfs              5.0M  4.0K  5.0M   1% /run/lock
tmpfs              3.9G     0  3.9G   0% /sys/fs/cgroup
/dev/sda9          1.9G  1.2G  571M  68% /opt
/dev/sda2           96M   33M   64M  34% /boot/efi
/dev/sda11         270G  210G   47G  82% /big
tmpfs              785M   44K  785M   1% /run/user/1000
/dev/sda10         4.5G  1.9G  2.4G  45% /work
/dev/mapper/proj   803M  278M  468M  38% /proj
/dev/mapper/codes  4.7M   60K  4.2M   2% /home/francis/e/codes

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https://bugs.launchpad.net/bugs/1875885

Title:
  luks cannot create small volumes < 8M

Status in cryptsetup package in Ubuntu:
  New

Bug description:
  I wanted to create a new luks image file, or actually increase the size of one that had overflowed.
  Each time I get the error message:

  Requested offset is beyond real size of device /work/e/tmp/codes.cryp.

  There is a suggestion this happens if you already have a luks drive
  mounted that is larger. I had nothing mounted through mapper.

  I successfully created my volume on 16.04, and 18.04. It fails on
  20.04 after clean boot, and one device mount "sudo mount /dev/sda10
  /work". I also mount /opt, and /big in my fstab

  I believe all versions have already been gathered.

  #!/bin/sh
  dd if=/dev/zero of=codes.cryp bs=1024 count=8000 # 4M volume
  sudo cryptsetup -vy luksFormat codes.cryp
  sudo cryptsetup luksOpen /work/e/tmp/codes.cryp codes
  sudo mkfs.ext4 /dev/mapper/codes
  sudo cryptsetup luksClose codes

  ProblemType: Bug
  DistroRelease: Ubuntu 20.04
  Package: cryptsetup 2:2.2.2-3ubuntu2
  ProcVersionSignature: Ubuntu 5.4.0-28.32-generic 5.4.30
  Uname: Linux 5.4.0-28-generic x86_64
  ApportVersion: 2.20.11-0ubuntu27
  Architecture: amd64
  CasperMD5CheckResult: skip
  CurrentDesktop: ubuntu:GNOME
  Date: Wed Apr 29 15:56:38 2020
  InstallationDate: Installed on 2020-04-26 (3 days ago)
  InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
  SourcePackage: cryptsetup
  UpgradeStatus: No upgrade log present (probably fresh install)
  cmdline: BOOT_IMAGE=/boot/vmlinuz-5.4.0-28-generic root=UUID=ea9a06e5-2ffa-4a3a-9ff9-096ea28d78f7 ro quiet splash vt.handoff=7
  crypttab: # <target name>	<source device>		<key file>	<options>

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