Proper way to join multi-volume tarballs?

Question

So how should this be done? I have learned that using cat is the preferred way when using split to create multi-volume files, but what about when using tar's own native multi-volume function?

Thanks

Answer 1

In this answer I give an answer using a callback script, to be used with the -F option of tar.

Here I expand on the automated input to tar prompt requests, both in the creation and the extraction of the archive, and estimating in advance the number of volumes needed:

#!/bin/bash
# CREATION SCRIPT

vol_size=100000

# estimated number of volumes: dir-size / vol-size + 1
# adding a further +1 to be safe
n=$(($(du -s Documents2 | awk '{ print $1 }') / $vol_size + 2))

for ((i = 2; i <= n; i++)); do printf 'n file-%d.tar\n' $i; done |
  tar -ML $vol_size -cf file-1.tar Documents2/ 2>&-

and

#!/bin/bash
# EXTRACTION SCRIPT

n=$(printf '%s\n' file-*.tar | sed 's/^file-//;s/\.tar$//' | sort -nr | head -1)
for ((i = 2; i <= n; i++)); do printf 'n file-%d.tar\n' $i; done |
  tar -M -xf file-1.tar 2>&-