I'd like an OS/FileSystem that Never Deletes Anything. Does it exist?

The expensive version of what you are describing is a vaulting appliance but I won't continue down that path unless you are a bank.

The affordable version of what you are describing is a set of NAS class servers that use something like DRBD or Ceph for multi-node replication and rsnapshot for local snapshots/versioning if LVM. If using LVM, then rsnapshot should be configured to save its snapshot where the remote clients can not write to it.

Look into setting up Ceph clusters if you plan to build something that will need to scale really large on individual volumes across multiple nodes. Ceph supports creating snapshots. There are pros and cons to solutions such as DRBD, LVM and Ceph. That would be a topic in and of itself. Others here are mentioning ZFS and that is also a popular solution but I have never used it and can't comment on it.

In summary if I was asked to build something that would grow to unknown size, require snapshots to roll-back files to a specific date and be fault tolerant I would go with Ceph. As a bonus feature there are libraries and tools to present Ceph volumes as S3-like buckets. There are ansible playbooks for setting up Ceph clusters. Ceph has some really good security features as well.

> Does a filesystem that never deletes/overwrites anything exist?

> Obviously once space runs out it would start overwriting the oldest versions.

You can’t have both.

Also, your system wouldn’t prevent data loss on hardware failures.

What you describe is/may be a WORM device (https://en.wikipedia.org/wiki/Write_once_read_many)

Digital's VMS/OpenVMS had something that was a fair way towards this, in that a file was created with a version number (myfile.txt;1) and when modified, a 2nd file (myfile.txt;2) was created, and so on...

In practice we used to work on things then purge when happy with the final changes, as we didn't have that much 'spare' disk, but it was a nice feature.

S3FS with versioning enabled on the S3 bucket would be a pretty low friction way to implement this. You'd also have to enable cross-region replication to deal with your "backups" being in the same place as your working copies.

OpenVMS also has a versioning filesystem and a NFS server. The x64 version is available as a private beta, but it's not cheap.

Personally, I just keep most stuff in a Google Drive folder and important stuff gets the keep versions forever bit turned on. Everything else goes in a git tree and have some automation to clone it to a reliable utility server when the OS thinks there's plenty of bandwidth available.

It's worth noting that the Google Drive solution is the only one that I've been able to get to work reliably across Linux, macOS, Windows, Android, and iOS. I've tried OneDrive, Dropbox, and iCloud Files, but they all have various problems with conflict resolution, annoying upselling, or limited file type support for versioning.

Just for reference, here are links to various old research papers referencing solutions to this scenario:

A list of options from a report:

https://www.fsl.cs.sunysb.edu/docs/secfs-rpe/index.html#tth_...

VersionFS:

https://www.fsl.cs.sunysb.edu/docs/versionfs-msthesis/index....

Elephant:

https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.70....

https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.129...

Silver:

https://www.usenix.org/system/files/conference/hotstorage16/...

Also possibly of interest, vfs:

https://github.com/FooSoft/vfs

I imagine something does exist that does this, but I do not know what it is called.

I know that overlayfs exists, which could enable this sort of thing by capturing each individual change to the filesystem as a new layer. https://www.kernel.org/doc/html/latest/filesystems/overlayfs...

Btrfs and ZFS can do snapshotting, and I would imagine it could be configured to snapshot at certain intervals or after individual changes to the filesystem or a section of the filesystem, like watched directories.

https://wiki.archlinux.org/title/Btrfs#Snapshots

https://docs.oracle.com/cd/E19253-01/819-5461/gbcya/index.ht...

There's also filesystem-in-userland tech like Fuse which could enable something like this. https://www.kernel.org/doc/html/latest/filesystems/fuse.html

On Windows, since 8.1, there is the built in File History. https://support.microsoft.com/en-us/windows/backup-and-resto...

On macOS, there is Time Machine built in. https://support.apple.com/en-us/HT201250

ZFS does have the concept of Snapshots but I would not consider that user friendly or useful for version tracking.

There is plenty of Version Control systems out there, like Git, again not user friendly for what you want.

Dropbox/OneDrive/Google Drive provide various levels of version tracking of changes.

I personally use Backblaze (30 days, continuous) and Tarsnap (45 days, nightly) for both off-site and temporal recovery when I really need it. Backblaze is used for "desktop" systems, Tarsnap for "server" systems.

Not exactly what you're asking for, but how about:

* use ZFS (or any snapshot capable file system)

* trigger snapshots at regular (short) intervals (as chosen by you).

ZFS snapshots are very low cost, and you can browse them using your normal file tools. You could reasonably snapshot every (say) 5 minutes, but I wouldn't try every second :)

> I'm tired creating backups, or loosing data. Let's be honest, sometimes it happens. Does a filesystem that never deletes/overwrites anything exist?

I use linux and system link the home folder to a Dropbox folder. There is an extended history option [1], so that you can go back a year for any file. I think it’s a reasonably close solution if you do not mind the cost and syncing to cloud.

[1]https://help.dropbox.com/files-folders/restore-delete/extend...

Look up "append only" filesystems. That'll get you most of the way there, but you'll have to manually reset things to get rid of old files. Or just use a competent backup system.

I think NilFS [0] fits your description, though it is somewhat obscure. It creates a checkpoint with every write, which can mounted after being turned into a snapshot.

Although the website seems to have not been updated in a while, it's mailing lists appear to be active. [1]

https://nilfs.sourceforge.io/en/ [0] https://marc.info/?l=linux-nilfs [1]

Maybe one option would be to host a WebDav share with the Delta-V extension (RFC 3253) backed by Subversion. An alternative to Subversion might me NextCloud which supports automatic versioning and WebDav, but I do not know if it supports versioning through WebDav.

I also desire an easy solution to this usecase.

Even if the perfect version of this exists, it will _not_ save you from needing backups. The FS can always screw up or the drive(s) go bad.

Is Apple Time Machine dead? Many years passed since I used my last one. But anyway,

I'm tired creating backups

Have you tried to automate them? Thousands of free and paid software to do that. Setup once, forget until next loss.

I hope this hypothetical OS never needs to use a swap file.

More seriously, in a time of unobtrusive automated backups and dirt cheap storage space, why is this such an issue where you want to have this kind of system?

I'd like the opposite - an FS which really deletes everything you command it to so no recovery tool would find (let alone recover) there was anything.

I think you can do this with fossil and venti

Check out Plan9’s Venti service?