[9fans] What happens to deleted files in 9front

[9fans] What happens to deleted files in 9front

[rc.upcsa]

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Hi all,
When a file is removed in 9front using rm, I take it that it is altogether deleted and non-recoverable. In Linux one can sometimes use specialised tools to recover files removed with rm. 



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Re: [9fans] What happens to deleted files in 9front

[hahahahacker2009]

> Hi all,
> When a file is removed in 9front using rm, I take it that it is altogether deleted and non-recoverable. In Linux one can sometimes use specialised tools to recover files removed with rm. 
> 

Why do you think that 9front will make it unrecoverable?
I haven't heard of any os that tries to make the file unrecoverable
when removed (e.g by zeroing it, or ``shred'')

> 

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Re: [9fans] What happens to deleted files in 9front

[ori]

Quoth rc.upcsa@gmail.com:
> Hi all,
> When a file is removed in 9front using rm, I take it that it is altogether deleted and non-recoverable. In Linux one can sometimes use specialised tools to recover files removed with rm. 
> 

well, on gefs, this happens:

        /sys/src/cmd/gefs/fs.c:1944:  fsremove(Fmsg *m, int id, Amsg **ao)

on hjfs, this happens:

        /sys/src/cmd/hjfs/fs1.c:923:  delete(Fs *fs, FLoc *l, Buf *b)

and on cwfs, this happens:

        /sys/src/cmd/cwfs/9p2.c:1303: doremove(File *f)

if your goal is to un-delete a file, you can run '9fs dump'
and get old revisions:

        % 9fs dump
        % ls /n/dump
        /n/dump/adm@day.2025.04.30_02:10:49
        /n/dump/adm@day.2025.04.30_08:21:24
        /n/dump/adm@day.2025.05.03_02:05:56
        <snip>
        /n/dump/main@minute.2026.01.27_03:41:01
        /n/dump/main@minute.2026.01.27_03:42:01
        /n/dump/main@minute.2026.01.27_03:43:01

gefs takes snapshots once a minute, deleting old ones;
cwfs does them nightly; I don't remember what hjfs does,
but I think it depends on cron.


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Re: [9fans] What happens to deleted files in 9front

[Noam Preil]

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If you know some of the contents of the file you can grep the storage device for it and maybe find the rest. It's useful for recovery by keyword in every system, at least for small files.

Some Linux tools would work fine if applied to a 9front drive too, since they work by scanning the block device for file signatures (e.g. image headers that say "this is a jpg") and those ll be the same on both.

The one exception would be venti/fossil but if you were using that you wouldn't be asking how to recover deleted files, so.

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Re: [9fans] What happens to deleted files in 9front

[cinap_lenrek]

Plan9 file-systems provide periodic snapshots.

9fs dump
ls /n/dump

So recoverying a deleted file can be as easy as:

cp /n/dump/YYYY/MMDD/path/to/file ...

See also: history(1)

The frequency and time of the snapshots depends
on the file-system being in use.

--
cinap

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Re: [9fans] What happens to deleted files in 9front

[Stuart Morrow]

> When a file is removed in 9front using rm, I take it that it is altogether deleted and non-recoverable. In Linux one can sometimes use specialised tools to recover files removed with rm.

It's not clear to me what exactly you're asking.  The last sentence
seems to narrow it down, but in fact doesn't, because you might be
referring to the 'cat /proc/.../fd' method on a living process that
still has the file.

"Filesystem filesystems" on Plan 9 mimic Unix's "unlink, not delete" behaviour.

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Re: [9fans] What happens to deleted files in 9front

[Charles Forsyth]

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> "Filesystem filesystems" on Plan 9 mimic Unix's "unlink, not delete"
> behaviour.


venti/fossil doesn't, and it's not a requirement.

h% file blimp
blimp: cannot open: 'blimp' file does not exist
h% echo still here >blimp
h% {sleep 10; cat}<blimp&
h% rm blimp
h% cat: error reading <stdin>: file has been removed

On Wed, 28 Jan 2026 at 20:42, Stuart Morrow <morrow.stuart@gmail.com> wrote:

> > When a file is removed in 9front using rm, I take it that it is
> altogether deleted and non-recoverable. In Linux one can sometimes use
> specialised tools to recover files removed with rm.
> 
> It's not clear to me what exactly you're asking.  The last sentence
> seems to narrow it down, but in fact doesn't, because you might be
> referring to the 'cat /proc/.../fd' method on a living process that
> still has the file.
> 
> "Filesystem filesystems" on Plan 9 mimic Unix's "unlink, not delete"
> behaviour.

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Re: [9fans] What happens to deleted files in 9front

[Charles Forsyth]

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it works in traditional Unix because files are really i-nodes and
the directories refer to them, but
even if the count is zero, they survive until a separately
reference-counted in-memory copy made by iget loses its final open-file
reference.
unless the system crashes before that event. oh no!


On Wed, 28 Jan 2026 at 23:14, Charles Forsyth <charles.forsyth@gmail.com>
wrote:

>
> "Filesystem filesystems" on Plan 9 mimic Unix's "unlink, not delete"
>> behaviour.
>
>
> venti/fossil doesn't, and it's not a requirement.
>
> h% file blimp
> blimp: cannot open: 'blimp' file does not exist
> h% echo still here >blimp
> h% {sleep 10; cat}<blimp&
> h% rm blimp
> h% cat: error reading <stdin>: file has been removed
>
> On Wed, 28 Jan 2026 at 20:42, Stuart Morrow <morrow.stuart@gmail.com>
> wrote:
>
>> > When a file is removed in 9front using rm, I take it that it is
>> altogether deleted and non-recoverable. In Linux one can sometimes use
>> specialised tools to recover files removed with rm.
>> 
>> It's not clear to me what exactly you're asking.  The last sentence
>> seems to narrow it down, but in fact doesn't, because you might be
>> referring to the 'cat /proc/.../fd' method on a living process that
>> still has the file.
>> 
>> "Filesystem filesystems" on Plan 9 mimic Unix's "unlink, not delete"
>> behaviour.

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Re: [9fans] What happens to deleted files in 9front

[ron minnich]

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I can not figure out what led you to conclude that files are deleted and
unrecoverable, ever. Are you using 9front or just reading documents?

Here's a useful one:
http://man.9front.org/1/yesterday

which has been around for, I guess, nearly 40 years?

But no, it's very very hard to lose a file in any version of Plan 9.

Going to systems like Linux is very depressing that way. It always feels
strange to me to be on any Unix system and realize files can be lost
irrevocably.

On Wed, Jan 28, 2026 at 7:42 AM <rc.upcsa@gmail.com> wrote:

> Hi all,
> When a file is removed in 9front using rm, I take it that it is altogether
> deleted and non-recoverable. In Linux one can sometimes use specialised
> tools to recover files removed with rm.
>
>
>
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Re: [9fans] What happens to deleted files in 9front

[rc.upcsa]

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Thanks all, this clears it up.

Just to be clear: I was not assuming 9front tries to make files unrecoverable. My question was really whether rm means "gone for good" in practice, compared with Linux where recovery tools are sometimes used.

The short answer seems to be: files are not deliberately shredded, and it's actually harder to lose data permanently on Plan 9 than on typical Linux setups.

I appreciate all the explanations, and I'll give some of the suggestions a try. 

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