Getting "Skipping backward is not possible on a pipe" after upgrade

Hello everybody.

Got a question (well, mostly to Denis, as usual :). I was invoking dar
like this for a long time:

sudo dar -c - -B ~/.darrc -R / exclude-path-washi-other > /mnt/storage/backup/washi-linux-2019.10.17-full.1.dar

There are really no relevant options in RC file other than compression /
silenced warnings / path and compression excludes.

The reason why I was running it like this is because I had it to read
the whole filesystem (thus root needed), but on the other had I needed
to write backup as normal user, as the /mnt/storage being a kerberized NFS
filesystem which root cannot write to. Unfortunately I lost ability to
split archives by size this way but I just had to deal with it.

However after some updates (currently there is dar 2.6.6 in my distro)
this command stopped working, producing error like this after some time
(backup is partially created at this point):

Detected Cache Directory Tagging Standard for /var/cache/man, the contents of that directory will not be saved
Final memory cleanup...
Error while saving data: Cannot write down the archive: Skipping backward is not possible on a pipe
Command exited with non-zero status 5

I have to admit I never understood chaining of multiple dar's or using
dar_xform so I'm a bit at loss at what to do now. This command was
working with dar 2.5 for sure. According to current 2.6 documentation
(http://dar.linux.free.fr/doc/usage_notes.html - "Single pipe") this
command still supposed to work. Only it doesn't.

What is wrong here and is there some other way I'm supposed to be doing
what I need here (read files as root, write backup as non-root user) in
2.6 version? Also, maybe there is some way to achieve this so that size
splitting will work as well?


$ dar -V
Warning: using insecure memory!

 dar version 2.6.6, Copyright (C) 2002-2019 Denis Corbin
   Long options support         : YES

 Using libdar 6.2.0 built with compilation time options:
   Libz compression (gzip)      : YES
   Libbz2 compression (bzip2)   : YES
   Liblzo2 compression (lzo)    : YES
   Liblzma compression (xz)     : YES
   Strong encryption (libgcrypt): YES
   Public key ciphers (gpgme)   : NO
   Extended Attributes support  : YES
   Large files support (> 2GB)  : YES
   ext2fs NODUMP flag support   : YES
   Integer size used            : 64 bits
   Thread safe support          : YES
   Furtive read mode support    : YES
   Linux ext2/3/4 FSA support   : YES
   Mac OS X HFS+ FSA support    : NO
   Detected system/CPU endian   : little
   Posix fadvise support        : YES
   Large dir. speed optimi.     : YES
   Timestamp read accuracy      : 1 microsecond
   Timestamp write accuracy     : 1 microsecond
   Restores dates of symlinks   : YES
   Multiple threads (libthreads): NO
   Delta compression support    : NO
   Remote repository support    : NO

 compiled the Sep 25 2019 with GNUC version 9.2.1 20190827 (Red Hat 9.2.1-1)
 dar is part of the Disk ARchive suite (Release 2.6.6)
 dar comes with ABSOLUTELY NO WARRANTY; for details
 type `dar -W'. This is free software, and you are welcome
 to redistribute it under certain conditions; type `dar -L | more'
 for details.


-- 

Vladimir