Re: Wiping a disk partition

On 7/9/25 12:29, Frank Leonhardt wrote:
> On 3 July 2025 22:20:31 BST, David Christensen <dpchrist@holgerdanske.com> wrote:
>> On 6/25/25 03:16, Odhiambo Washington wrote:
>>> root@gw:/home/wash # df -h
>>> Filesystem     Size    Used   Avail Capacity  Mounted on
>>> /dev/ada0p2    1.8T    552G    1.1T    33%    /
>>> devfs          1.0K      0B    1.0K     0%    /dev
>>> fdescfs        1.0K      0B    1.0K     0%    /dev/fd
>>> procfs         8.0K      0B    8.0K     0%    /proc
>>> linprocfs      8.0K      0B    8.0K     0%    /compat/linux/proc
>>> linsysfs       8.0K      0B    8.0K     0%    /compat/linux/sys
>>> /dev/ada1p2    1.8T    856G    802G    52%    /disk2
>>
>>
>> On 7/3/25 02:24, Odhiambo Washington wrote:
>>> What I did was:
>>>
>>> umount /disk2
>>> dd if=/dev/ada0 of=/dev/ada1 bs=1g status=progress
>>
>>
>> If the computer was running in multi-user mode when you cloned ada0 to ada1, the root file system on ada0p2 will have been mounted read-write, any ada0 swap partition will have been active, and it is likely that foreground and/or background processes wrote to ada0 while cloning.  The last means the source and the clone are not the same, and the backup is incorrect.
>>
>>
>> If you want to clone ada0 to ada1, then you must boot into single-user mode or boot live media; so that ada0 does not change while cloning. After making the clone, verify by using cmp(1) to do a byte-for-byte comparison of the source and the clone.
> 
> 
> Or just copy the partition in question rather than the whole drive.


So long as the destination partition is the same size or larger than the 
source partition, and both are not in use.  But for OS disks, I prefer 
the clone the entire disk so that the MBR, GPT tables, ESP, and all of 
the various boot loader stages are consistent.


> On multitasking system you can always put an & on the end of the rm command and let it run in the background. Probably the safest way to delete all the files if you're sure.


TIMTOWDI.


David