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Full Discussion: HP-UX 10.20 devices
Operating Systems HP-UX HP-UX 10.20 devices Post 14652 by Kelam_Magnus on Monday 4th of February 2002 02:08:06 PM
Old 02-04-2002
/dev/zero vs /dev/null
Since yall brought this up, I have a question.

What is the difference between. These two commands

1) cat /dev/null > somefile

2) cat /dev/zero > somefile

3) > somefile



Zeroing out a file.

I know that "dd can be used to create a file of X bytes for testing and to "hold" space in a filesytem and for doing "disk dumps" an d for destroying data on a disk ( not the prescribed method).

I think I know another reason for /dev/zero. That would be to zero out a disk for reuse.

Any insight would be informative.

Smilie Smilie
 

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LEARN ABOUT HPUX

vxdestroy_lvmroot

vxdestroy_lvmroot(1M)													     vxdestroy_lvmroot(1M)

NAME

       vxdestroy_lvmroot - remove LVM root disk and associated LVM volume group

SYNOPSIS

       vxdestroy_lvmroot [-v] [-b] lvm_root_disk

DESCRIPTION

       The  vxdestroy_lvmroot  command	tears  down  and removes the LVM volume group associated with the specified physical disk. This is done by
       removing the volumes in the volume group and then removing the volume group.

OPTIONS

       -b	 Invokes the setboot command to change the primary boot disk to the VxVM root disk from which the system was booted (if  the  pri-
		 mary  boot  disk is not already set to this disk).  The alternate boot device remains unchanged.  If the -v option is also speci-
		 fied, the settings of the primary and alternate boot devices are displayed.

       -v	 Outputs verbose messages including a timestamp that indicates major operations being performed.

ARGUMENTS

       lvm_root_disk
	    Specifies the device name of the LVM root disk that is to be destroyed, along with its entire volume group.

EXAMPLES

       This example shows the vxdestroy_lvmroot command invoked in its simpliest form:

       /etc/vx/bin/vxdestroy_lvmroot c5t1d0

       # /etc/vx/bin/vxdestroy_lvmroot -v -b c3t0d0
       Are you sure about destroying c3t0d0 (imported on VG /dev/vg02) ? YES
       vxdestroy_lvmroot 06:02: Tearing down /dev/vg02 on device c3t0d0
       vxdestroy_lvmroot 06:02:
	 Unmounting and removing any volumes associated with /dev/vg02
       vxdestroy_lvmroot 06:02: removing logical volume /dev/vg02/lvol1
       vxdestroy_lvmroot 06:02: removing logical volume /dev/vg02/lvol2
       vxdestroy_lvmroot 06:02: removing logical volume /dev/vg02/lvol3
       vxdestroy_lvmroot 06:02: removing logical volume /dev/vg02/lvol4
       vxdestroy_lvmroot 06:02: removing logical volume /dev/vg02/lvol5
       vxdestroy_lvmroot 06:02: removing logical volume /dev/vg02/lvol6
       vxdestroy_lvmroot 06:02: removing logical volume /dev/vg02/lvol7
       vxdestroy_lvmroot 06:02: removing logical volume /dev/vg02/lvol8
       vxdestroy_lvmroot 06:02: Removing Volume Group /dev/vg02
       vxdestroy_lvmroot 06:02: Removing device files in /dev/vg02
       vxdestroy_lvmroot 06:02: Removing LVM Physical Volume c3t0d0
       vxdestroy_lvmroot 06:02: Removing LVM Physical Volume c1t1d3
       vxdestroy_lvmroot 06:02: Removing LVM Physical Volume c1t1d4
       vxdestroy_lvmroot 06:02: Removing LVM Physical Volume c1t1d5
       vxdestroy_lvmroot 06:03: Current setboot values:
       vxdestroy_lvmroot 06:03: Primary:       0/0/6/0/0.0.0
       vxdestroy_lvmroot 06:03: Alternate:     0/0/1/0/0.1.0
       vxdestroy_lvmroot 06:03:
	 Making disk c0t1d0 (0/0/1/0/0.1.0) the primary boot disk
       vxdestroy_lvmroot 06:03:
	 Removal of device c3t0d0, volume group /dev/vg02 was successful

SEE ALSO

       cpio(1), dd(1), fsck(1M), setboot(1M) vxbootsetup(1M) vxcp_lvmroot(1M) vxres_lvmroot(1M)

VxVM 5.0.31.1							    24 Mar 2008 					     vxdestroy_lvmroot(1M)
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