How do you set bzip2 block size when using tar?

Question

I am using tar to backup a linux server to tape. I am using the -j option to compress the file with bzip2, however I can't see a way to adjust the block size options for bzip2 from tar. The default block size is 900,000 bytes which gives the best compression but is the slowest. I am not that bothered about the compression ratio, so am looking to make bzip2 run faster with a smaller block size.

Answer 1

export BZIP=--fast
tar cjf foo.tar.bz2 foo

Or pipe the output of tar to bzip2.

Though you should note from the bzip2 man page:

    -1 (or --fast) to -9 (or --best)
              Set  the  block size to 100 k, 200 k ..  900 k when compressing.
              Has no effect when decompressing.  See MEMORY MANAGEMENT  below.
              The --fast and --best aliases are primarily for GNU gzip compat-
              ibility.  In particular, --fast  doesn't  make  things  signifi-
              cantly faster.  And --best merely selects the default behaviour.

Answer 2

Send the tar output to stdout and then pipe it through bzip2 separately:

% tar cvf - _file_ | bzip2 _opts_ > output.tar.bz2

Answer 3

Its even easier:

% tar -cvf dir.tar path/to/dir/ && bzip2 -9 dir.tar