[Bug 722910] Re: xz fails with hardlink errors on ntfs partition

[xhienne]

This is the normal (yet unexplained AFAIK) behavior of many compression
tools like gzip, bzip2 and xz, to refuse to compress a file with a link
count > 1, unless you give the --force option. The actual questions here
are "why do my NTFS files have a link count of 2?" (see
COMP6366_V01_02_15_2011.wmv in the OP) and "why does this link count
drop to 1 when I rename the file?"

This is due to the DOS name mangling system (see
https://en.wikipedia.org/wiki/Filename_mangling and
https://en.wikipedia.org/wiki/8.3_filename). When a file (say
"TextFile.Mine.txt") was copied on the NTFS partition with a 8.3 mangled
filename (say "TEXTFI~1.TXT"), then it is presented by the ntfs-3g
driver only once, in its long form. But the file continues to be
accessible by both names: "TEXTFI~1.TXT" (hidden) and
"TextFile.Mine.txt" (displayed). Hence the link count of 2, one for each
name. And this is also why the link count drops to 1 when you rename the
file: the mangled version disappear.

You may want to reassign this bug to the ntfs-3g package, arguing that
the link count should be 1. Personally I don't think this is an obvious
bad choice but others may disagree.

So, what else? Should we close this bug? Actually, I don't think so. I
think it should be renamed to "Gzip / bzip2 / xz refuse to compress
files with a link count > 1". As said above, I have yet to read a good
reason for gzip/bzip2/xz to _refuse_ to compress a file with more than
one hard link. Even with the --keep option! Why not just a mere warning?
Imposing a --force flag on e.g. script writers for the sole reason that
files may have many hard links, does not seem quite safe to me.

gzip is a very old program (25 years old?). My guess is that this is an
unfortunate legacy of a formerly legitimate behavior (for security
reasons for example?) which has absolutely no raison d'être nowadays.
bzip2 and xz have just blindly copied gzip's interface.

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https://bugs.launchpad.net/bugs/722910

Title:
  xz fails with hardlink errors on ntfs partition

Status in bzip2 package in Ubuntu:
  Confirmed
Status in xz-utils package in Ubuntu:
  Confirmed

Bug description:
  Binary package hint: xz-utils

  After mounting an ntfs partition using dolphin in kubuntu, xz fails to compress any file on the ntfs partition.
  $ [sudo] xz -9 COMP6366_V01_02_15_2011.wmv 
  xz: COMP6366_V01_02_15_2011.wmv: Input file has more than one hard link, skipping

  More information about the file:
  $ ls -la COMP6366_V01_02_15_2011.wmv 
  -rwxrwxrwx 2 root root 332122239 2011-02-15 16:36 COMP6366_V01_02_15_2011.wmv

  Workaround: Renaming the file will allow xz to perform the compression.
  $ mv COMP6366_V01_02_15_2011.wmv COMP6366_V01_02_15_2011.wmv2 && mv COMP6366_V01_02_15_2011.wmv2 COMP6366_V01_02_15_2011.wmv
  $ xz -9 COMP6366_V01_02_15_2011.wmv
  After mounting an ntfs partition using dolphin in kubuntu, xz fails to compress any file on the ntfs partition.
  $ [sudo] xz -9 COMP6366_V01_02_15_2011.wmv 
  xz: COMP6366_V01_02_15_2011.wmv: Input file has more than one hard link, skipping

  More information about the file:
  $ ls -la COMP6366_V01_02_15_2011.wmv 
  -rwxrwxrwx 2 root root 332122239 2011-02-15 16:36 COMP6366_V01_02_15_2011.wmv

  Workaround: Renaming the file will allow xz to perform the compression.
  $ mv COMP6366_V01_02_15_2011.wmv COMP6366_V01_02_15_2011.wmv2 && mv COMP6366_V01_02_15_2011.wmv2 COMP6366_V01_02_15_2011.wmv
  $ xz -9 COMP6366_V01_02_15_2011.wmv
  $ ls -la COMP6366_V01_02_15_2011.wmv.xz 
  -rwxrwxrwx 1 root root 325158580 2011-02-15 16:36 COMP6366_V01_02_15_2011.wmv.xz

  Any file that is modified or placed onto the ntfs partition from
  within ubuntu is fine - this bug only exists for files that already
  existed on my Windows XP system.

  $ lsb_release -rd
  Description:    Ubuntu 10.10
  Release:        10.10
  $ xz -V
  xz (XZ Utils) 4.999.9beta
  liblzma 4.999.9beta
  $ apt-cache policy xz-utils
  xz-utils:
    Installed: 4.999.9beta+20100527-1
    Candidate: 4.999.9beta+20100527-1
    Version table:
   *** 4.999.9beta+20100527-1 0
          500 http://us.archive.ubuntu.com/ubuntu/ maverick/main amd64 Packages
          100 /var/lib/dpkg/status

  ProblemType: Bug
  DistroRelease: Ubuntu 10.10
  Package: xz-utils 4.999.9beta+20100527-1
  ProcVersionSignature: Ubuntu 2.6.35-23.40-generic 2.6.35.7
  Uname: Linux 2.6.35-23-generic x86_64
  NonfreeKernelModules: nvidia
  Architecture: amd64
  Date: Mon Feb 21 18:39:05 2011
  InstallationMedia: Kubuntu 9.10 "Karmic Koala" - Release amd64 (20091027)
  ProcEnviron:
   LANGUAGE=
   PATH=(custom, user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: xz-utils

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