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Re: Zerofree won't run with LiveCD

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On 2026-03-31, Paul <nospam@needed.invalid> wrote:
> On Tue, 3/31/2026 10:52 AM, George Garth wrote:
>> On 3/31/26 9:07 AM, Paul wrote:
>>> On Tue, 3/31/2026 4:34 AM, George Garth wrote:
>>>> On 3/30/26 8:17 PM, Paul wrote:
>>>>> On Mon, 3/30/2026 4:46 PM, George Garth wrote:
>>>>>> One of my other tasks, aside from the cleansing of Win drives using Sdelete and other tools, was to also cleanse the free space of Ubuntu partitions.
>>>>>>
>>>>>> A prior post mentioned the use of Zerofree, but it has to be done on unmounted partitions.  Today, I brought out an old LiveDVD with 16.04 on it then installed Zerofree via apt.  I then  listed the partitions and found the one I needed, /dev/sdb2, but trying to run sudo zerofree /dev/sdb2, I get the following error:  failed to open file system: /dev/sdb2.  I then tried to create a mount point (mkdir: /mnt/temp) and then mounted /dev/sdb2 onto that point, but a new error about something not in GRUB.
>>>>>>
>>>>>> Suggestions welcome for getting this up and running and thanks in advance.
>>>>>
>>>>> My notes file says:
>>>>>
>>>>> sudo zerofree -v /dev/sdb1  # fill with zeros, before compaction in host
>>>>>                               # /dev/sdb1 should not be mounted when you run it
>>>>>
>>>>> *******
>>>>>
>>>>> Do a "df" or a "cat /etc/mtab" and check what is mounted, as
>>>>> /dev/sdb1 should not be mounted for the example to work.
>>>>>
>>>>> *******
>>>>>
>>>>> https://manpages.ubuntu.com/manpages/focal/man8/zerofree.8.html
>>>>>
>>>>>          zerofree - zero free blocks from ext2, ext3 and ext4 file-systems
>>>>>
>>>>>          -n         Perform a dry run  (do not modify the file-system);
>>>>>
>>>>>          -v         Be verbose: show the number of blocks modified by zerofree (or that would be modified, in  case
>>>>>                     the -n is used), the number of free blocks and the total number of blocks on the filesystem;
>>>>>
>>>>>          -f value   Specify the octet value to fill empty blocks with (defaults to 0). Argument must be within the
>>>>>                     range 0 to 255.
>>>>>
>>>>>      Paul
>>>>
>>>> Ok, well, I finally got it to run.... sort of.  I'll try to explain. I'm not all that well versed in Linux particulars other than plug and play, but here goes....
>>>>
>>>> Booted into Ubuntu from a USB for a session. Did a "df" as suggested to find:
>>>>
>>>> https://imgur.com/a/1RR4Yna
>>>>
>>>> Unmount /dev/sda2 to be sure and then tried to run Zerofree:
>>>>
>>>> https://imgur.com/a/IkkZCWb
>>>>
>>>>
>>>> The only way I could get Zerofree to run was to do:
>>>>
>>>> sudo zerofree -v /dev/sda8 and then the same except for sda7.
>>>>
>>>> Tried the swap as well but to no avail:
>>>>
>>>> https://imgur.com/a/r6eaAoT
>>>>
>>>>
>>>> So, my guess is that the program is not recognizing the extended sda2 for some reason.
>>>> I'm going to assume that since I was able to use it on sda7 & 8, I should be ok, but why not working for the swap?
>>>
>>> Now that I've had time to bask in the beauty of this mess :-)
>>>
>>> This looks like you have installed Ubuntu on the disk. Maybe
>>> you booted then, from the Live Media, as a means of not mounting
>>> the partitions. Note - this was done via OCR and editing, so
>>> there could be errors. I converted the picture.
>>>
>>> Device     Boot      Start       End    Sectors     Size Id Type
>>> /dev/sda1   *         2048    206847     204800     100M  7 HPFS/NTFS/exFAT
>>> /dev/sda2           208894 409602047  409393154   195.2G  5 Extended
>>> /dev/sda3        409602048 974992494  565390447   269.6G  7 HPFS/NTFS/exFAT
>>> /dev/sda4        974993408 976769023    1775616     867M 27 Hidden NTFS WinRE
>>> /dev/sda5           208896  15831039   15622144     7.4G 82 Linux swap / Solaris
>>> /dev/sda6         15833088  19736575    3903488     1.9G ef EFI (FAT-12/16/32)
>>> /dev/sda7         19738624  88096767   68358144    32.6G 83 Linux
>>> /dev/sda8         88098816 409602047  321503232   153.3G 83 Linux
>>>
>>> That's an MSDOS partitioned disk, with Extended/Logical.
>>> The last four partitions are logicals and fit precisely into the extended
>>> declared in sda2. At first I was concerned the disk was "severely overlapped",
>>> but that's because I wasn't parsing it right. I don't think it is overlapped.
>>> I was thrown off by the contents of sda6.
>>>
>>> But the 0xef as sda6, it looks like the OS was not willing to do a
>>> fallback installation into sda1. sda1 is declared as the boot partition,
>>> by having 0x80 for the boot flag in sda1. The 0xef should not have
>>> been created. *This smells like UBUNTU*. So what would be inside
>>> that 0xef. Probably something we can't use. Now it depends
>>> on what Stage1 boot code is in Sector0, either the Windows MSDOS
>>> boot stage (that looks for the partition with the boot flag), or
>>> the sector could contain a Ubuntu boot sector in Sector0 (which
>>> might look for an EFI partition by type). We would know, based
>>> on which OS boots at startup. If Windows starts and Ubuntu is inaccessible,
>>> then Windows uses Sector0. If Ubuntu starts, and OSProber was present,
>>> the Ubuntu GRUB menu could offer both Ubuntu and Windows, and Windows
>>> (maybe) gets chain-loaded if it is selected.
>>>
>>> When the Live Media boots, the swap partition will get mounted
>>> when the OS does a "sudo swapon /a" or "use all swap partitions please".
>>>
>>> Doing a   sudo swapoff /dev/sda5   would cause that partition to be
>>> released. But really, there is no point doing that, because
>>> zerofree only processes EXT2/3/4 and not a swap.
>>>
>>> Since sda2 is an Extended partition, there is no file system there.
>>> You cannot zerofree that either. The Extended is a very short allocation
>>> of space. A mere pimple. A couple blocks after that the first Logical starts.
>>>
>>> Summary: This setup isn't actually illegal, but the boot process is
>>>           unlikely to be the best job ever. I could see this starting
>>>           every time, putting up a GRUB menu and so on. But if Canonical
>>>           thinks this is going to Secure Boot, I don't think so.
>>>
>>> Just when you think you've seen it all.
>>>
>>>     Paul
>> 
>> 
>> Lol, interesting analysis, but I would have to read it several times to begin understanding.  Yes, this is a dual boot system with selectable Win 10 or Ubuntu at start up.  When Win is active, Ubuntu is not accessible.  However, I can access the Win partition when in Ubuntu.
>> 
>> So I guess you're saying that the sda2 is actually MSDOS.  Interesting. Well, bringing up "Disks" in Ubuntu right now, I see that "Extended Partition 2" consists of swap, sda7/8, and, yes, sda6 as FAT.
>> 
>> Whew, I hope I'm done shredding free space now because, between doing this for the Win partition and drives, and then in Ubuntu, I've had more than enough.  In the future, I'm simply not going to save anything sensitive to be deleted later only to have to go through this all over again which, in a year, I'll forget the entire process.
>> 
>> If there's some sloppiness with the way the partitions are set up, the only thing I can say is that I used some web instructions or videos to set everything up and probably installed from the Live CD.  I don't know enough to configure any better way.  I seldom use Win and debated even setting it up the last time, but there are just those times when I need to do things on that OS that would be difficult or impossible for me to do in Linux.
>> 
>> Appreciate your input.  Your initial suggestion to use Zerofree was tried, but I encountered issues from the beginning and then, when I had more time, to make a determined effort to get it going.
>> 
>
> As someone trying to help, I have a conundrum when it comes to offering advice.
> If I catch a situation, early on, I may be able to recommend a recipe
> that puts the situation "on a more solid footing". But most users follow
> a risk/reward model. They are not going to do something, unless there is
> an easy-to-observe benefit.
>
> There are two disk partitioning schemes. MSDOS (<2.2TB drives) and GPT
> (>2.2TB drives). Your drive is small enough, either could be used.
> You can plug in a 24TB HDD, use MSDOS partitioning, and basically
> throw away the 22TB area at the end. In the beginning, we
> were only promoting GPT, if the user had a really big disk.
>
> But the progression of the industry right now, is "Exclusive UEFI" booting
> and ideally "Secure Boot" (getting some benefit from UEFI). The easiest
> way to do this, is GPT partitioning.
>
> Many Windows 10 users in 2015, they installed Windows in MSDOS partitioning
> mode. Since Windows 8, a utility has been included called "MBR2GPT.exe" and
> it reworks a small number of partitions (it refuses to touch an Extended/Logical
> disk). Because the number of partitions it will handle is so small (three partitions
> out of four max), for a lot of progressive users, that utility is useless.
> This was not written by a regular staffer, it violates the "we only do one
> operation at a time via primitives" rule of disk software. It's a software
> where you should have a backup, not because the software is bad, but
> because the "approach" is "too too brave".
>
> If your Win10 disk had been "transitioned" to GPT (and the machine is
> modern enough to have UEFI, which is not a given), then your install of
> Ubuntu would have been neat and tidy, there would have been no
> Extended/Logical, no "partitions out of order" declarations and so on.
> By making this sort of transition at the right time, we can step
> away from MSDOS partitioning, and not even have to "wash up" after
> the work is finished. But it's a hell of a lot of work for
> a "trust me, you'll appreciate this later" thing. Nobody here
> volunteers for those, if I were to suggest it.
>
> On the other hand, once the disk is Spaghettios, cleanup is
> a lot more difficult, and again, it I say "nuke and pave"
> I will get "aw, do I HAVE to?".
>
> And this happens, not because as users, we are bad people,
> it happens because the computing industry has stuck
> "multiple forks in the road" with "inadequate toolage to clean up".
> The Intels, the Microsofts, they don't give a fuck that your
> only option is to reinstall and reinstall all your programs.
> But I care. I hardly ever "clean install" because of
> an industry trap, but I work damn hard to battle this crap.
>
> When I look at your disk, I'm saying to myself "I hope that
> doesn't bite him further down the road". Since Win10 is
> out-of-support, that stabilizes things, a lot. I am
> less worried now. If that had been Win11, now I'd be
> nervous (25H2, 26H2, 27H2... "um, it won't install").
>
> Summary: The next time you're doing an OS hard drive,
>          consider GPT partitioning and UEFI boot, as installs
>          go a lot smoother that way. And since GPT supports
>          128 partitions max, you don't have to worry about sda79
>          being the last one you are allowed :-)
>
My impression is as you have a mess, or not best practice, you system is
"damaged" and do a reinstall from scratch when you have the time and energy.
As it is you are likely to find yourself in a very deep swamp. 

A final tip, into the habit of making notes when you do something new. The
time and effort will pay off given time.



>    Paul
>
>

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Thread

Zerofree won't run with LiveCD George Garth <none@nowhere.com> - 2026-03-30 16:46 -0400
  Re: Zerofree won't run with LiveCD Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-03-30 23:48 +0000
  Re: Zerofree won't run with LiveCD Paul <nospam@needed.invalid> - 2026-03-30 20:17 -0400
    Re: Zerofree won't run with LiveCD George Garth <none@nowhere.com> - 2026-03-31 04:34 -0400
      Re: Zerofree won't run with LiveCD Mike Scott <usenet.16@scottsonline.org.uk.invalid> - 2026-03-31 12:14 +0100
        Re: Zerofree won't run with LiveCD Paul <nospam@needed.invalid> - 2026-03-31 07:52 -0400
        Re: Zerofree won't run with LiveCD George Garth <none@nowhere.com> - 2026-03-31 08:12 -0400
          Re: Zerofree won't run with LiveCD Jeff Layman <Jeff@invalid.invalid> - 2026-03-31 16:30 +0100
      Re: Zerofree won't run with LiveCD Josef Möllers <josef@invalid.invalid> - 2026-03-31 14:38 +0200
        Re: Zerofree won't run with LiveCD George Garth <none@nowhere.com> - 2026-03-31 08:51 -0400
      Re: Zerofree won't run with LiveCD Paul <nospam@needed.invalid> - 2026-03-31 09:07 -0400
        Re: Zerofree won't run with LiveCD George Garth <none@nowhere.com> - 2026-03-31 10:52 -0400
          Re: Zerofree won't run with LiveCD Paul <nospam@needed.invalid> - 2026-03-31 16:17 -0400
            Re: Zerofree won't run with LiveCD Gordon <Gordon@leaf.net.nz> - 2026-04-01 03:50 +0000
              Keeping notes (was Re: Zerofree won't run with LiveCD) Josef Möllers <josef@invalid.invalid> - 2026-04-01 14:51 +0200
                Re: Keeping notes (was Re: Zerofree won't run with LiveCD) Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-04-01 20:42 +0000
                Re: Keeping notes (was Re: Zerofree won't run with LiveCD) Josef Möllers <josef@invalid.invalid> - 2026-04-03 11:28 +0200
          Re: Zerofree won't run with LiveCD Paul <nospam@needed.invalid> - 2026-05-06 02:08 -0400

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