Untar on empty partition returns ENOSPACE

[Jean-Denis Girard <jd.girard@sysnux.pf>]

Hi list,

My goal is to duplicate some SD cards, to prepare 50 similar Raspberry Pi.

First, I made a tar of my master SD card (unmounted). Then I made a
script, which creates 2 partitions (50 MB for boot, 14 GB for /),
creates the file-systems (vfat and btrfs, default options), mounts the
two partitions:

mount $part2 $mnt
-ocompress=zstd,space_cache=v2,autodefrag,noatime,nodiratime
mkdir $mnt/boot
mount $part1 $mnt/boot

When untarring, I get many errors, like:
tar:
./usr/lib/libreoffice/share/gallery/arrows/A45-TrendArrow-Red-GoUp.png :
open impossible: No space left on device
tar:
./usr/lib/libreoffice/share/gallery/arrows/A53-TrendArrow-LightBlue-TwoDirections.svg
: open impossible: No space left on device
tar:
./usr/lib/libreoffice/share/gallery/arrows/A27-CurvedArrow-DarkRed.png :
open impossible: No space left on device
tar:
./usr/lib/libreoffice/share/gallery/arrows/A41-CurvedArrow-Gray-Left.svg
: open impossible: No space left on device

Which usually results in unusable SD card.

When the first errors occur, less than 1 GB has been written. I tried to
change mount options, especially commit interval, but still got ENOSPACE.

What I ended up doing is limiting write speed with:
xzcat $archive | pv -L 4M | tar x
(with -L 5M I start to get a couple of errors)

Is there a better work around? Or a patch to test that could help?

The machine that runs the script has:
[jdg@tiare tar-install]$ uname -r
4.19.0-rc7-snx
[jdg@tiare tar-install]$ btrfs version
btrfs-progs v4.17.1


Thanks,
-- 
Jean-Denis Girard

SysNux                   Systèmes   Linux   en   Polynésie  française
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