Backups & restore

Two player-facing restore mechanisms protect your state, while a third internal transaction backup protects each setup, update, or migration from a partial filesystem change.

Table of contents

The player-facing mechanisms at a glance

  Snapshot files Previous-version backup (.bak)
What it is Timestamped folders of your personal state files A full copy of your previous-version install (the whole instance at the previous version)
Where %APPDATA%\PrismLauncher\instances\Craft to Exile 2\.negativezone\backups\<yyyyMMdd-HHmmss>\ %APPDATA%\PrismLauncher\instances\Craft to Exile 2.bak\ (shows in Prism’s grid as a separate instance)
Contains Waypoints, world map cache, shaders, resourcepacks, options, recipe bookmarks, plus pack-author-flagged config files (graphics, shaders, HUD, sound prefs, keybinds) Mods, configs, resourcepacks, libraries — the whole game install at the prior version
Does not contain Single-player worlds (opt-in), mods, configs not in the pack-author preserve list — (it’s a complete instance)
Created by nz backup PostExit hook (every Prism close) nz setup when it detects an upgrade (existing instance, different version)
Cadence At most once per NEGATIVEZONE_BACKUP_DAYS (default 3 days) of play; one is also forced just before nz update touches tracked pack files One per modpack upgrade you go through
Retention NEGATIVEZONE_BACKUP_RETAIN newest (default 3) Latest only — each new upgrade overwrites the previous .bak
Size 100 MB – 2 GB each, depending on how much you’ve explored 3 – 6 GB
Restore = ? Manual file copy back into .minecraft\ Launch the generated Craft to Exile 2 (old) instance
Has launch hooks? (file collection, no scripts) The (old) copy has hooks disabled; multiplayer still requires the admin to roll back the server

Every nz setup, nz update, or nz migrate that replaces an existing instance also creates a checksum-verified full backup under %APPDATA%\PrismLauncher\instances\.negativezone-backups\. It is used by the transaction journal and is not the normal player restore interface. If an operation is interrupted, close Prism and rerun the same command; do not delete the journal, stage, rollback, or transaction-backup folders.

Snapshot files (periodic state backups)

Every Prism session end runs nz backup which snapshots a curated set of your personal client state. This catches accidents that packwiz-managed updates don’t handle: world corruption from a mod crash, files deleted by mistake, unexpected pack changes, etc.

How it works

When the game closes, Prism runs nz backup (its PostExitCommand) which:

  1. Checks the timestamp of your newest snapshot. If it’s less than 3 days old (configurable), the script exits in ~100 ms — no perceptible delay before Prism shows the instance as stopped.
  2. If a snapshot is due, it copies a curated allow-list into .negativezone\backups\<timestamp>\ using robocopy (fast — multi-GB Xaero map caches take ~10–20 s).
  3. Prunes to the 3 newest snapshots so disk usage stays bounded.

Each snapshot is a self-contained tree mirroring the original layout under .minecraft\, so restore is just copy back.

The update step also forces one snapshot right before every modpack update, so update day always has a fresh restore point even if your last periodic snapshot was 2 days ago.

What’s snapshotted

By default (lean profile, ~100 MB – 2 GB per snapshot depending on exploration):

  • XaeroWaypoints\ — every server waypoint you’ve placed
  • XaeroWorldMap\ — explored map cache (the dominant size term)
  • screenshots\, shaderpacks\, resourcepacks\
  • config\jei\ and config\emi\ (recipe-viewer bookmarks)
  • options.txt, optionsof.txt, optionsshaders.txt, servers.dat, usercache.json, usernamecache.json
  • The pack-author user-prefs manifest — every mod-config file the pack treats as user-tunable (Embeddium graphics, Oculus shaders, Xaero map style, HUD layout, sound prefs, keybinds, etc.). The current list lives at packwiz/.user-prefs.txt in the repo and is bundled into each pack release as <instance>\.negativezone\preserve-list.json.

Notably not included by default: .minecraft\saves\ — most players connect to the multiplayer server so client saves are empty. If you play single-player worlds in this instance too, opt in with the env var below.

Tuning or disabling

Open PowerShell and set any of these in your user environment (they persist across reboots; restart Prism for them to take effect):

Variable Purpose Default
NEGATIVEZONE_BACKUP_DAYS Days between snapshots (0 = every exit) 3
NEGATIVEZONE_BACKUP_RETAIN How many snapshots to keep 3
NEGATIVEZONE_BACKUP_INCLUDE_SAVES Set to 1 to also snapshot single-player worlds (adds GBs) unset
NEGATIVEZONE_BACKUP_DISABLE Set to 1 to disable backups entirely unset

Example — keep 5 weekly snapshots that include single-player worlds:

[Environment]::SetEnvironmentVariable('NEGATIVEZONE_BACKUP_DAYS',          '7', 'User')
[Environment]::SetEnvironmentVariable('NEGATIVEZONE_BACKUP_RETAIN',        '5', 'User')
[Environment]::SetEnvironmentVariable('NEGATIVEZONE_BACKUP_INCLUDE_SAVES', '1', 'User')

Restoring user state from a snapshot

  1. Close Prism.
  2. Open %APPDATA%\PrismLauncher\instances\Craft to Exile 2\.negativezone\backups\ in File Explorer.
  3. Pick the snapshot you want — folders are named yyyyMMdd-HHmmss so the newest is alphabetically last.
  4. Copy the files/directories you want to restore back into %APPDATA%\PrismLauncher\instances\Craft to Exile 2\.minecraft\, overwriting the current ones.
  5. Reopen Prism and launch.

Previous-version backup (.bak rollback)

When nz setup runs an upgrade (finds an existing instance with a different version), it transactionally installs and validates the new version, then copies the verified previous payload to Craft to Exile 2.bak and creates a launchable Craft to Exile 2 (old) copy. Both sit alongside the current instance in Prism’s Backup group.

What it’s for

A safety raft for two narrow cases:

  1. “The new version broke something and the admin hasn’t fixed it yet.” While the admin rolls the server back (or pushes a hotfix), you’ve got the previous client version ready to go without re-downloading.
  2. Offline play of the old version — useful if you want to compare UI/config behaviour between versions, or replay a single-player world built on the old mod set.

What it’s not for

  • Joining the live server with a version mismatch. If you launch the .bak instance while the server is already on the new version, the server will kick you at the FML handshake. The .bak is only useful for multiplayer if the admin has also rolled the server back to that version.
  • A long-term archive. Each new upgrade overwrites the previous .bak — there is no .bak.bak deep history. If you want to keep an old version forever, copy the Craft to Exile 2.bak folder under %APPDATA%\PrismLauncher\instances\ somewhere off-instance before your next upgrade.

Raw .bak versus launchable (old)

The .bak is a byte-for-byte copy of your old instance, including its launch hooks. Those hooks reference an absolute path that now points at your current instance’s nz.exe. The generated Craft to Exile 2 (old) copy disables those hooks, so use (old) for a clean offline launch. Treat .bak as the cold filesystem rollback source:

  • For a real multiplayer rollback, the admin rolls the server back and you re-run nz update (the admin sets allowDowngrade in the manifest).
  • For offline single-player on the old mod set, launch (old).

Using it

  1. In Prism’s instance grid, find Craft to Exile 2 (old) under Backup.
  2. Click it, then Play as normal. If the server is still on a different version, expect an FML-handshake kick on join — that’s fine, you’re not breaking anything.

“Which one do I want?” — restore scenarios

Symptom Use How
Lost a single waypoint / setting after an update Snapshot files Copy that one file/dir from the newest snapshot back into .minecraft\
All my Xaero waypoints + explored map are gone Snapshot files Copy back XaeroWaypoints\ and XaeroWorldMap\ from the newest snapshot
Keybinds reset Snapshot files Copy options.txt back
Server list cleared / lost the entry Snapshot files Copy servers.dat back
The new modpack version has a client-side bug; I need to play yesterday’s version while the admin fixes it Previous-version copy Launch Craft to Exile 2 (old). It only works for multiplayer if the admin also rolled back.
I want yesterday’s modpack and my latest waypoints Both Launch (old) once to verify it boots, then copy XaeroWaypoints\ from the newest snapshot into that instance’s .minecraft\
Something deleted my whole .minecraft\config\ directory Snapshot files (partial) + re-run install (full) Restore the pack-author preserve-list files from snapshot for your tunings, then re-run the Path A one-liner to repopulate the rest of the configs from the pack defaults

Disk usage at a glance

Worst-case footprint of the safety net (without NEGATIVEZONE_BACKUP_INCLUDE_SAVES):

  • 3 snapshot folders × up to ~2 GB each = ~6 GB
  • .bak plus (old) ≈ 6–12 GB after a setup upgrade
  • one 3–6 GB immutable full backup for each changing setup, update, or migration

Transaction backups are intentionally not automatically pruned. If disk usage becomes a problem, send nz support output to the admin before removing old, completed transaction directories.

If you turn on single-player saves in snapshots, multiply the snapshot portion by however large your saves/ directory is.