Hello, I am confused by a warning from mkswap : When making a swap on a LVM volume, I see the following warning : mkswap: /dev/vg_SDB1/swap_test6_64: warning: don't erase bootbits sectors on whole disk. Use -f to force. Setting up swapspace version 1, size = 1048572 KiB Is it safe to use mkswap -f in this case ? (If that matters, the swap is intended for a virtual machine, and the host where I am using mkswap is a CentOS-6 server.) Thanks, -- Philippe Naudin
On Tuesday 13 March 2012 13.41.53 Philippe Naudin wrote:> Hello, > > I am confused by a warning from mkswap : > > When making a swap on a LVM volume, I see the following warning : > mkswap: /dev/vg_SDB1/swap_test6_64: warning: don't erase bootbits > sectors on whole disk. Use -f to force. > Setting up swapspace version 1, size = 1048572 KiB > > Is it safe to use mkswap -f in this case ?I'd say it's safe but why do it? What likely happened is that the lv you ran mkswap on contained a valid partition table (or at least boot signature). Out of paranoia mkswap left the first block alone. So what you could gain is maybe another 512 byte in swapspace by adding -f. You could write a meg of zeroes to the device first and see if the mkswap warning goes away. /Peter> (If that matters, the swap is intended for a virtual machine, and > the host where I am using mkswap is a CentOS-6 server.) > > Thanks,-------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 198 bytes Desc: This is a digitally signed message part. URL: <http://lists.centos.org/pipermail/centos/attachments/20120313/7e43cb89/attachment-0004.sig>
Peter Kjellstr?m wrote:> On Tuesday 13 March 2012 13.41.53 Philippe Naudin wrote: >> Hello, >> >> I am confused by a warning from mkswap : >> >> When making a swap on a LVM volume, I see the following warning : >> mkswap: /dev/vg_SDB1/swap_test6_64: warning: don't erase bootbits >> sectors on whole disk. Use -f to force. >> Setting up swapspace version 1, size = 1048572 KiB >> >> Is it safe to use mkswap -f in this case ? > > I'd say it's safe but why do it? > > What likely happened is that the lv you ran mkswap on contained a valid > partition table (or at least boot signature). Out of paranoia mkswap left > the first block alone. So what you could gain is maybe another 512 byte in > swapspace by adding -f.<snip> Are you making swap from a logical partition, or a swapfile? If the former, perhaps recreating the partition might help. mark