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cp: -r or -R?

126 points · 110 comments · zdw

  1. krn1p4n1c · · focus · HN ↗
    tar cf - . | tar xf - -C <dest>
    1. Rygian · · focus · HN ↗
      with a sandwiched `| pv |` for fun stats
      1. dspillett · · focus · HN ↗
        And `| ssh <target> ` for a remote copy.

        (or ssh <target> prepended rather than sandwiched, to copy from remote)

        1. Rygian · · focus · HN ↗
          At some point it starts very much looking like zfs send | pv | ssh <target> zfs receive
          1. krn1p4n1c · · focus · HN ↗
            Seriously. I do wish ZFS was everywhere.
        2. krn1p4n1c · · focus · HN ↗
          I usually sandwich zstd and base64 encode/decode in with the ssh pipe. Used when I need root permissions to pull the remote dirs.
          1. dspillett · · focus · HN ↗
            You shouldn't need to B64 encode for transfer - piping over SSH is binary safe. Verifying with 100Mbyte of random data:

                user@host:/tmp$ cat rnd.file | sha256sum
    71d3392be59210c517ab889fca715a46dee54f6326a9d901db0addd351607cb6  -
    user@host:/tmp$ cat rnd.file | ssh user@otherhost sha256sum
    71d3392be59210c517ab889fca715a46dee54f6326a9d901db0addd351607cb6  -
    user@host:/tmp$ cat rnd.file | zstd -z | ssh user@otherhost "zstd -d | sha256sum"
    71d3392be59210c517ab889fca715a46dee54f6326a9d901db0addd351607cb6  -
            When using zstd (or anything else) make sure you don't have something in your .sss/config that would make ssh use a compression as you'll waste a bit of CPU to send a little more data as a less efficient compression method is applied on top. Though TBH I think that unless I'm on a very slow link, if I'm sending something big enough to need compression it is probably in a pre-compressed or otherwise uncompressable format anyway (video, photos, …) so zstd does little, the one exception I can think of being if I'm throwing an unencrypted VM image from place to place.
    2. jhallenworld · · focus · HN ↗
      I never bothered to learn -C, instead I use:

          tar -cf - . | (cd <dest>;  tar -xf -)
      For doing something like duplicating root of a filesystem you may want --one-file-system.
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