Re: recover deleted file

Hi warner,
Thanks for trying :)

Actually my use case was (if you read later replies, i gave up since the
downtime was too long and couldn't wait more) a VM in ESXi.
so all the underlying stuff of the disks/TRIM.. is hidden an
inaccessible for me (hosting provider).

In my case I tried to recover MariaDB database files, and some tar.gz file
of backups of the db that I accidentally deleted all together (mysql*
instead of mysql/*  , my bad, deleted mysql/ & mysql_backups!!). I stopped
all services immediately, so maybe I would succeed if I wasn't time limited.

I understand its hard to undelete since no one designed UFS/ZFS to do so..
that why I asked in later replies to see if someone would step in and
implement such a "feature" and I suggested some directions/thoughts.

As soren@ suggested in later reply it maybe would be easier to implement
custom rm script that moves files to "Recycle bin" directory (and empty it
after some period) but as a programmer I know that perfection is needed :)
so It might start as a simple task and end in many what-if's
(unfortunattly I did my last C programming in late 2003!).

What amzes me is that this "feature" was asked too much in the last decade
or two and no one ever implemented it, maybe it's not needed in daily
usage, but in disasters it would be super userful, save admins many time
and nerves..

For now I did some backup tools locally and used chflags to mark them
undeletable so I wouldn't do that mistake again, plus I rsync them to my
home storage.. so probably I would be more resilent to such mistakes in the
future.. but the same problem remains.. accidently deleted
file(s)/directory(s) are the nightmare of all admins in earth!!

Sami

On Sun, Apr 17, 2022 at 12:42 AM Warner Losh <imp@bsdimp.com> wrote:

>
>
> On Sat, Apr 16, 2022 at 5:24 AM Sami Halabi <sodynet1@gmail.com> wrote:
>
>> Hi,
>> is there anyway easy to restore deleted file by accident in UFS????
>>
>
> Do you know what the contents of the file is? At least the first, say,
> ~32k?
>
> The problem with unrm for ufs is that the directory entry has the inode
> number stored in it.
> Without the inode number, you won't get very far.
> With the inode number, you can get the first 12 filesystem blocks of the
> file and the
> first three indirect blocks. Once you have those, you can reconstruct the
> file.
>
> But only if the inode hasn't been zero'd out (which it likely has, another
> thing that makes
> UFS undelete harder). But all hope isn't lost...  UFS has a predictable
> allocation algorithm
> that lets you get much of the file back (which is why I asked if you know
> how it should start:
> you can find where it starts in the data blocks and maybe get lucky with
> the rest if the
> data spills into indirect blocks).
>
> However, that's only if you don't have TRIM enabled on the filesystem. If
> you do,
> then UFS will do a BIO_DELETE of the blocks, which means their contents are
> likely gone at the drive level. I say likely because there's weasel words
> in the ATA
> spec that allows a drive to return the prior contents of the blocks, or
> all zeros or
> the drive's initialization pattern (usually all 1's) when the blocks are
> later read. Same
> goes for NVMe drives (with the additional constraint it must be
> deterministic). So there's
> may still be a chance you can read the old contents, but drives that do
> that are rare
> in my experience (which is admittedly quite narrow).
>
> But, if you want to use fsdb to try to recover this data, or write your
> own tools,
> then you should likely have a copy of the daemon book (The Design and
> Implementation
> of the FreeBSD Operating System). It explains a lot of the finer details
> of UFS and
> reference to it likely will catch me where my memory isn't quite right in
> the above
> descriptions.
>
> So, it's for all these reasons you can't find somebody with a unrm command
> for ufs
> like you can for DOS or other filesystems. I wish I had a better answer
> for you.
>
> Warner
>
>
>> Sami
>>
>> --
>> Sami Halabi
>> Information Systems Engineer
>> NMS Projects Expert, FreeBSD SysAdmin Expert
>> Asterisk Expert
>>
>

-- 
Sami Halabi
Information Systems Engineer
NMS Projects Expert, FreeBSD SysAdmin Expert
Asterisk Expert