On Mon, Aug 17, 2020 at 11:35:39AM -0500, Eric Blake wrote:
While iflag=count_bytes combined with bs > 1 allows for more efficient operation, it is a feature of GNU dd, and not present on other implementations such as BSD. Sticking to just POSIX features makes things more portable.
I'm not very convinced by this. Maybe we should persuade the BSD folk to implement this useful feature instead? As one example:
diff --git a/docs/nbdkit-loop.pod b/docs/nbdkit-loop.pod index 055b5750..b21c2212 100644 --- a/docs/nbdkit-loop.pod +++ b/docs/nbdkit-loop.pod @@ -120,7 +120,7 @@ creates a disk which contains a bad sector: echo EIO Bad block >&2 exit 1 else - dd if=/dev/zero count=$3 iflag=count_bytes + dd bs=1 if=/dev/zero count=$3 fi ;; *) exit 2 ;; esac
this change could be a killer for performance since the suggested size of the disk is 64M. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/