I wanted to dump the first 16KB of L2 of ZFS on my disk to examine it when debugging a bootloader issue, but that failed with the following: # dd if=/dev/sda1 of=/tmp/start bs=512 count=32 skip=240056884736 dd: ‘/dev/sda1’: cannot skip: Invalid argument 0+0 records in 0+0 records out 0 bytes (0 B) copied, 0.000485126 s, 0.0 kB/s I suspect that dd uses 32-bit values for the skip parameter.
As a workaround you can do: # dd if=/dev/sda1 of=/tmp/tmp-start bs=32768 count=1 skip=3750888824 # dd if=/dev/tmp-start of=/dev/start bs=16384 count=1 And of course try the current stable.
still happen in 8.20 ? how about USE=gmp ? (i don't remember if that affects dd ...)
can't reproduce w/8.20 on x86_64 or x86 system x86_64 (64bit): $ strace -e lseek dd if=/dev/zero of=/dev/null bs=512 count=32 skip=240056884736 lseek(0, 0, SEEK_CUR) = 0 lseek(0, 122909124984832, SEEK_CUR) = 0 32+0 records in 32+0 records out 16384 bytes (16 kB) copied, 0.00341417 s, 4.8 MB/s +++ exited with 0 +++ or on a real device: # strace -e lseek dd if=/dev/md0 of=/dev/null bs=1 count=1 skip=240056884736 lseek(0, 0, SEEK_CUR) = 0 lseek(0, 240056884736, SEEK_CUR) = 240056884736 1+0 records in 1+0 records out 1 byte (1 B) copied, 0.0160826 s, 0.1 kB/s +++ exited with 0 +++ x86 (32bit): $ strace -e _llseek dd if=/dev/zero of=/dev/null bs=512 count=32 skip=240056884736 _llseek(0, 0, [0], SEEK_CUR) = 0 _llseek(0, 122909124984832, [0], SEEK_CUR) = 0 32+0 records in 32+0 records out 16384 bytes (16 kB) copied, 0.0030879 s, 5.3 MB/s or on a real device: # strace -e _llseek dd if=/dev/md0 of=/dev/null bs=1 count=1 skip=240056884736 _llseek(0, 0, [0], SEEK_CUR) = 0 _llseek(0, 240056884736, [240056884736], SEEK_CUR) = 0 1+0 records in 1+0 records out 1 byte (1 B) copied, 0.000848877 s, 1.2 kB/s
