Comments on: Howto : Resume a failed copy command where it left off http://hartvig.de/2008/howto-resume-a-failed-copy-command-where-it-left-off/ Personal homepage of Kaare Hartvig Jensen Mon, 02 Apr 2012 06:05:11 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Trevor Joynson http://hartvig.de/2008/howto-resume-a-failed-copy-command-where-it-left-off/#comment-97232 Trevor Joynson Fri, 30 Mar 2012 05:44:14 +0000 http://hartvig.de/?p=32#comment-97232 Using a blocksize other than 1 helped me out with CPU usage quite a bit, and acted as a nice buffer across my network transfers, ala mbuf esque. Sorry to spam your blog, but here's my final variation if anyone's interested: #!/bin/bash -e # Blocksize to truncate to and buffer by BS=${BS:-4096} death() { echo "$0:" "$@" >&2; exit 1; } [ $# -eq 2 ] || death "Usage: $0 original copy" SRC="$1"; DST="$2" # Got SRC? [ -f "$SRC" ] || death "$SRC: No such file" # Calculate the number of bytes to skip before we start copying. Default to zero. SKIP=0; [ ! -f "$DST" ] || SKIP=$(( $(wc --bytes "$DST" | awk '{print $1}' ) / $BS )) # Do the actual copying. echo dd if="$SRC" of="$DST" conv=notrunc bs=$BS skip="$SKIP" seek="$SKIP" Using a blocksize other than 1 helped me out with CPU usage quite a bit, and acted as a nice buffer across my network transfers, ala mbuf esque. Sorry to spam your blog, but here’s my final variation if anyone’s interested:

#!/bin/bash -e

# Blocksize to truncate to and buffer by
BS=${BS:-4096}

death() { echo “$0:” “$@” >&2; exit 1; }

[ $# -eq 2 ] || death “Usage: $0 original copy”
SRC=”$1″; DST=”$2″

# Got SRC?
[ -f "$SRC" ] || death “$SRC: No such file”

# Calculate the number of bytes to skip before we start copying. Default to zero.
SKIP=0; [ ! -f "$DST" ] || SKIP=$(( $(wc –bytes “$DST” | awk ‘{print $1}’ ) / $BS ))

# Do the actual copying.
echo dd if=”$SRC” of=”$DST” conv=notrunc bs=$BS skip=”$SKIP” seek=”$SKIP”

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