![]() This example clears the disk if it has data partitions, but not if it also has OEM partitions. Example 2: Clear a disk with data partitions PS C:\> Clear-Disk -Number 1 -RemoveData This example clears disk number one only if it does not contain both data or OEM partitions. Examples Example 1: Clear a blank disk PS C:\> Clear-Disk -Number 1 This cmdlet will not clear OEM recovery partitions unless RemoveOEM parameter is also specified. If the disk contains active data volumes, then the RemoveData parameter is required as this will delete all data from the specified disk. The Clear-Disk cmdlet clears the disk by removing the partition and volume information. LVM does this cleanup job for you.Cleans a disk by removing all partition information and un-initializing it, erasing all data on the disk. ![]() So this is just for completeness that you can hit the warning with pvcreate as well as with lvcreate where it's even more important. Then LVM calls the libbblkid's "wipefs" code to wipe any signatures it finds and after that it drops the "private" flag and hence any udev hook (or anyone listening on udev events) sees newly created LV with clean data area, which is what we expect normally. If you answer "y" here, LVM activates the LV with a flag marking that device as private temporarily so udev does not scan the LV's data area yet and hence there shouldn't be any automatic actions in background based on the event. This is just an example, but it applies to any other signatures too. If you answered "n" for the question above, LVM would not remove the old signature and if there's a hook in udev by chance which, for example, does automatic mounting, you could end up with unexpected behavior where you have these automatic actions firing in background without you knowing about them. WARNING: ext2 signature detected on /dev/vg/lvol0 at offset 1080. (and now, let's call lvcreate which "by chance" finds old FS signature) Writing superblocks and filesystem accounting information: done (just calling this to create an FS signature and simulate old signature for the lvcreate later)Ĭreating filesystem with 4096 1k blocks and 1024 inodes But with lvcreate, the LV data area is allocated in runtime and the offset and segments are calculated during that lvcreate so you never know with what offset and where to call wipefs before calling lvcreate - it's quite low level action anyway). However, when creating new LVs and when you hit this warning, I recommend answering "yes" to wipe the signature because otherwise there may be udev hook which would automatically activate whatever old signature there was from any previous use in just allocated LV's data area (IOW, with pvcreate, you know the offset - the PV signature is written at the beginning of the disk. It's OK to run wipefs yourself before calling pvcreate, like Bryn mentioned. You may see such warning with pvcreate (as in the scenario reported here) as well as with lvcreate where LVM runs this signature detection code from libbblkid on newly created LV data area. So this is exactly the same code as blkid and wipefs uses - they both use this library too. ![]() LVM uses libblkid (which is from util-linux) and calls the signature detection code from this library. > from the 'file' package on most distros. > Both blkid and wipefs are from util-linux. ![]() > will also report label offsets as with pvcreate). > and optionally back it up to a file so that it can be restored (it > You can also use the wipefs program to manually remove any signature, > /dev/sda1: Linux rev 1.0 ext4 filesystem data, UUID=49f9b992-3c68-4b59-a232-e1a3a4482eed (needs journal recovery) (extents) (large files) (huge files) > If you want to confirm what's present on a device, use the blkid or > 1 existing signature left on the device. > WARNING: vfat signature detected on /dev/sda5 at offset 54.
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