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GNU tar blocking factor, blocks, records and checkpoints

by mfincham on 8/26/20, 9:55 PM with 5 comments

• by throw0101a on 8/26/20, 11:21 PM

  > Because tar operations may be long running, it can be useful to have feedback about progress during the operation.

  For those running on a system that has SIGINFO (e.g., BSD, macOS?), hit ^T and you'll get a status report to stderr. ^T should work for various other utilities as well: dd, cp, ftp.

  On those systems that do not have SIGINFO (Linux?), but are using bsdtar (libarchive), SIGUSR1 will do the same:

  * https://github.com/libarchive/libarchive/search?q=SIGINFO

  INFO isn't one of the mandatory POSIX signals:

  * https://en.wikipedia.org/wiki/Signal_(IPC)#POSIX_signals

• by kevin_thibedeau on 8/27/20, 12:12 AM

  Tar is a convenient format for basic embedded data storage since it's easy to parse and you don't have to build custom tooling to prepare them. We'd store small pre-gzipped web resources in a tar file and send them out as is without needing onboard compression. The blocking factor puzzled me for a bit when I was trying to store a few hundred bytes and couldn't understand where the extra 10k was coming from. Sometimes you have to RTFM.