[ I noticed that using a starting address of "1MiB" evokes a warning,
along with the obviously unintended start sector of 34:
parted -s -- $dev mklabel gpt mkpart PARTITION-NAME 1MiB -34s
Warning: The resulting partition is not properly aligned for best
performance.
While the following, with "1048576B", works fine and creates the partition
starting at the desired 1MiB address:
parted -s -- $dev mklabel gpt mkpart PARTITION-NAME 1048576B -34s
]
I made parted tell me why it was treating "1MiB" differently from
"1048576B". Bottom line is that if you use a large unit, like MiB, it
assumes you're being sloppy, but if you specify bytes or sectors, you
require exactness (radius = 0). That may have made sense when people
used sloppy units like MB (1,000,000), but obviously does not hold for
most people who bother to type "MiB".
Here's a proposed patch to make the command I gave work the way I
intended. Opinions welcome. On one hand, I don't particularly like
treating 1MiB differently from 1MB, but if someone is using 1MB and
intends 1MiB, they need a little wake up call (or some RTFM).
[the full patch will include a documentation update as well as
a couple of tests to illustrate/exercise the difference. ]
In the mean time, to get the proper 1MiB alignment, you'll have to
use an explicit byte or sector count. I prefer byte counts, in spite of
the greater number of digits, because that works the same regardless
of a disk's sector size:
dev=...
k=1024 m=$((k*k))
parted -s -- $dev mklabel gpt mkpart P-NAME ${m}B -34s
diff --git a/libparted/unit.c b/libparted/unit.c
index 2670c38..59a9644 100644
--- a/libparted/unit.c
+++ b/libparted/unit.c
@@ -480,6 +480,12 @@ parse_unit_suffix (const char* suffix, PedUnit
suggested_unit)
return suggested_unit;
}
+static bool
+is_power_of_2 (long long n)
+{
+ return (n & (n - 1)) == 0;
+}
+
/**
* If \p str contains a valid description of a location on \p dev, then
* \p *sector is modified to describe the location and a geometry is created
@@ -530,6 +536,13 @@ ped_unit_parse_custom (const char* str, const PedDevice*
dev, PedUnit unit,
radius = ped_div_round_up (unit_size, dev->sector_size) - 1;
if (radius < 0)
radius = 0;
+ /* If the user specified units in a power of 2, e.g., 1MiB, as in
+ parted -s -- $dev mklabel gpt mkpart P-NAME 1MiB -34s
+ do not use 1MiB as the range. Rather, presume that they
+ are specifying precisely the starting or ending number,
+ and treat "1MiB" just as we would treat "1048576B". */
+ if (is_power_of_2 (unit_size))
+ radius = 0;
*sector = num * unit_size / dev->sector_size;
/* negative numbers count from the end */
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