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authorJim Meyering <meyering@redhat.com>2010-06-14 10:15:57 +0200
committerJim Meyering <meyering@redhat.com>2010-06-14 22:36:28 +0200
commitceb84598d8c3a166e6949606710771f58eb2be56 (patch)
tree333e8c6aa4ab460f0c888702fcb39f2b428b4a86 /doc
parent280b15249c9983d61707a00b6a462eb1df448c78 (diff)
downloadcoreutils-ceb84598d8c3a166e6949606710771f58eb2be56.tar.xz
doc: dd: discourage use of very large block sizes
* doc/coreutils.texi (dd invocation): Warn against using a very large block size. Suggested by Imre PĂ©ntek.
Diffstat (limited to 'doc')
-rw-r--r--doc/coreutils.texi5
1 files changed, 5 insertions, 0 deletions
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 26b4eba64..102ceaf97 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -8020,6 +8020,11 @@ followed by a multiplier: @samp{b}=512, @samp{c}=1,
@samp{w}=2, @samp{x@var{m}}=@var{m}, or any of the
standard block size suffixes like @samp{k}=1024 (@pxref{Block size}).
+Any block size you specify via @samp{bs=}, @samp{ibs=}, @samp{obs=}, @samp{cbs=}
+should not be too large---values larger than a few megabytes
+are generally wasteful or (as in the gigabyte..exabyte case) downright
+counterproductive or error-inducing.
+
Use different @command{dd} invocations to use different block sizes for
skipping and I/O@. For example, the following shell commands copy data
in 512 KiB blocks between a disk and a tape, but do not save or restore a