PMAX_BOOT_BLOCK_OFFSET
rv = pread(params->fsfd, &bb, sizeof(bb), PMAX_BOOT_BLOCK_OFFSET);
rv = pwrite(params->fsfd, &bb, sizeof(bb), PMAX_BOOT_BLOCK_OFFSET);
rv = pread(params->fsfd, &bb, sizeof(bb), PMAX_BOOT_BLOCK_OFFSET);
startblock = PMAX_BOOT_BLOCK_OFFSET / PMAX_BOOT_BLOCK_BLOCKSIZE
rv = pwrite(params->fsfd, &bb, sizeof(bb), PMAX_BOOT_BLOCK_OFFSET);