[Bug 1929087] Re: sfdisk refuses to write GPT table between sector 34 and 2047

[Bill Yikes]

A secondary bug manifests from this, whereby sfdisk chokes on its own
output and therefore cannot restore its own backup.  E.g. suppose
another tool is used to put a BIOS boot partition from sector 34 to
2047, as follows:

$ sgdisk --clear -a 1 --new=1:34:2047 -c 1:"BIOS boot"
--typecode=1:$(sgdisk --list-types | sed -ne
's/.*\(....\).bios.*/\1/gip') /dev/sdb

That works fine, and from that we can run "sfdisk -d /dev/sdb >
dump.txt".  But when dump.txt is fed back into sfdisk, it pukes.  Yet
the docs claim "It is recommended to save the layout of your devices.
sfdisk supports two ways." .. "Use  the  --dump  option to save a
description of the device layout to a text file." .. "This can later be
restored by: sfdisk /dev/sda < sda.dump"

It's actually a security issue, because someone can make an non-
restorable backup and have the false sense of security that it is
restorable.  They wouldn't necessary test restoration either because
that's a destructive process.

** Description changed:

  According to https://wiki.archlinux.org/title/GRUB#BIOS_systems, it's
  both legal and interesting to place the BIOS BOOT partition from sector
  34 to sector 2047, as follows:
  
  $ sudo sfdisk --no-act -f --label gpt /dev/sdb << EOF
  start=       34, size=2013,             name=bios,       type=$(sfdisk --label gpt -T | awk '{IGNORECASE = 1;} /bios boot/{print $1}')
  start=     2048, size=12582912,         name=swap,       type=$(sfdisk --label gpt -T | awk '{IGNORECASE = 1;} /linux swap/{print $1}')
  EOF
  
  The output is:
  
  /dev/sdb1: Sector 34 already used.
  Failed to add #1 partition: Numerical result out of range
  Leaving.
  
- It's a false error.  As a workaround, users must omit the BIOS BOOT
- partition then use gdisk to insert it manually.  This was uncovered in
- 2015 and perhaps never reported to a bug tracker because it's still
- broken.  See https://www.spinics.net/lists/util-linux-ng/msg11253.html
+ It's a false error.  As a workaround, users must use parted or sgdisk
+ instead.  (note fdisk & gdisk are also broken in the same way)
+ 
+ This bug was uncovered in 2015 and perhaps never reported to a bug
+ tracker because it's still broken.  See https://www.spinics.net/lists
+ /util-linux-ng/msg11253.html

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https://bugs.launchpad.net/bugs/1929087

Title:
  sfdisk refuses to write GPT table between sector 34 and 2047

Status in util-linux package in Ubuntu:
  New

Bug description:
  According to https://wiki.archlinux.org/title/GRUB#BIOS_systems, it's
  both legal and interesting to place the BIOS BOOT partition from
  sector 34 to sector 2047, as follows:

  $ sudo sfdisk --no-act -f --label gpt /dev/sdb << EOF
  start=       34, size=2013,             name=bios,       type=$(sfdisk --label gpt -T | awk '{IGNORECASE = 1;} /bios boot/{print $1}')
  start=     2048, size=12582912,         name=swap,       type=$(sfdisk --label gpt -T | awk '{IGNORECASE = 1;} /linux swap/{print $1}')
  EOF

  The output is:

  /dev/sdb1: Sector 34 already used.
  Failed to add #1 partition: Numerical result out of range
  Leaving.

  It's a false error.  As a workaround, users must use parted or sgdisk
  instead.  (note fdisk & gdisk are also broken in the same way)

  This bug was uncovered in 2015 and perhaps never reported to a bug
  tracker because it's still broken.  See https://www.spinics.net/lists
  /util-linux-ng/msg11253.html

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