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Bug#770789: marked as done ([tech-ctte] df sizes output format)



Your message dated Mon, 15 Dec 2014 13:17:26 -0800
with message-id <20141215211725.GT31486@rzlab.ucr.edu>
and subject line Re: Bug#770789: Draft of option for #770789
has caused the Debian Bug report #770789,
regarding [tech-ctte] df sizes output format
to be marked as done.

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-- 
770789: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=770789
Debian Bug Tracking System
Contact owner@bugs.debian.org with problems
--- Begin Message ---
Package: tech-ctte
Severity: normal
X-Debbugs-Cc: 761424@bugs.debian.org

As reported in #761424, the "sizes" output by df(1) are not actual sizes, due to the "units" used. The "units" used are merely unit prefixes. Moreover, df uses the same pseudo-units with different meanings. The output can therefore be misleading if one attempts to interpret it. 2 different calls seem to give different measurements for the same filesystems:
chealer@debian:~$ LANG=C df -h
Filesystem                                              Size  Used Avail Use% Mounted on
rootfs                                                  1.8T  317G  1.4T  19% /
udev                                                     10M     0   10M   0% /dev
tmpfs                                                   252M  5.4M  247M   3% /run
/dev/disk/by-uuid/a00f8767-e954-4b81-8035-c6bb414671cb  1.8T  317G  1.4T  19% /
tmpfs                                                   5.0M  4.0K  5.0M   1% /run/lock
tmpfs                                                   961M     0  961M   0% /run/shm
/dev/sdb2                                               2.2G  122M  2.0G   6% /tmp
chealer@debian:~$ LANG=C df -H
Filesystem                                              Size  Used Avail Use% Mounted on
rootfs                                                  2.0T  340G  1.6T  19% /
udev                                                     11M     0   11M   0% /dev
tmpfs                                                   264M  5.7M  259M   3% /run
/dev/disk/by-uuid/a00f8767-e954-4b81-8035-c6bb414671cb  2.0T  340G  1.6T  19% /
tmpfs                                                   5.3M  4.1k  5.3M   1% /run/lock
tmpfs                                                   1.1G     0  1.1G   0% /run/shm
/dev/sdb2                                               2.4G  128M  2.2G   6% /tmp
chealer@debian:~$

In the first example call, JEDEC prefixes are used, while SI prefixes are used in the second.

Michael Stone denies, excusing the behavior with space scarcity, documentation, and what he considers as little impact:
I'm not going to deviate from upstream. [...] The 
space is more important (in my opinion) than the need for a constant 
reminder of the unit. The documentation is there for people to read the 
first time, after that it's just not that important. (Even for the 
numbers above the difference isn't really significant--the relative 
sizes are the consistent, and what are the odds that you need exactly 12 
gigasomethings? If you did need exactly that much space, you're probably 
better off looking at kbytes or bytes anyway.)

The space scarcity and impact arguments do not hold, and unfortunately, even the documentation does not define the pseudo-sizes currently output.
-- 
Filipus Klutiero
http://www.philippecloutier.com

--- End Message ---
--- Begin Message ---
user tech-ctte@packages.debian.org
usertag 770789 published

On Sat, 13 Dec 2014, Don Armstrong wrote:
> I will announce the decision on -announce shortly.

Announced; closing this bug.

-- 
Don Armstrong                      http://www.donarmstrong.com

You could say to the Universe this is not /fair/. And the Universe
would say: Oh it isn't? Sorry.
 -- Terry Pratchett _Soul Music_ p357

--- End Message ---

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