Sysible Flashback

Contents

1. Overview

Sysible Flashback is the config time machine. Every host running a Sysible agent sends its tracked configuration files in, and Flashback keeps every version of every one of them — so the question "what did this file look like before the change, and who changed it" has an answer that does not depend on anyone having remembered to take a backup.

From the console you can, for any host and any file:

• read every stored version, newest first
• view a version in the browser
• download it
• diff any two versions of it
• restore a version back to the host
• compare the same path across the whole fleet, to find the box that drifted

Flashback ships inside the SLOP stack and is reached at https://<server-ip>/flashback/. It needs no separate install.

For the platform it runs in — installation, accounts, TLS and single sign-on — see the Sysible Linux Operations Platform guide.

What it is not

It is not a general backup system. It stores configuration files, not data volumes, databases or whole filesystems — and it stores *changes*, not a copy per day. For machine-level backup and restore, use the Controller's backup tooling.

2. How a version gets here

Nothing is pulled. The host's agent pushes a snapshot of its tracked files, and Flashback records a new version of a file only when its content differs from that file's most recent stored version. A fleet that is not changing produces almost no new rows, which is what makes keeping every version affordable.

The capture is driven by the Controller: it is the Controller's Flashback wiring that tells agents what to capture and where to send it. If that wiring is missing, no host can capture anything, and the console says so once at the top of the hosts column rather than letting every row read as a stale agent.

Capturing on demand

You do not have to wait for the next poll. The hosts column offers:

• Back up now on a single host's row
• Back up all for the whole fleet
• Back up selected for the hosts you tick — the unit an operator usually

actually wants, since environments are how fleets are run

A capture is a request, not an instruction executed inline: the host's agent performs it on its next check-in, so rows stop saying "no backup captured yet" on their own shortly afterwards.

3. Finding things

Hosts

Hosts are grouped by environment, the same grouping the rest of the suite uses, because a flat list of opaque host identifiers tells an operator nothing about which box they are looking at. Groups fold, and on a large fleet they start folded.

Above the list is a filter. It matches the host name, its identifier, its address and its environment, so typing prod finds the production group and web finds the web boxes wherever they live. A match inside a folded group opens that group rather than hiding the result.

Files

A host here typically has several hundred to a thousand captured files, so the files column has its own filter. Terms are space-separated and all must match, in any order — x11 session finds /etc/X11/Xsession without you having to remember how the path is spelled. The count beside the box says how many of the total are showing.

Both filters stay pinned to the top of their column while the list scrolls, and Escape clears either one.

4. Reading a version

Pick a host, then a file, then a version. The versions column shows each stored version with its timestamp, size and content hash, newest first and marked current.

With a version selected you get four actions:

View this version renders the file in the browser. A binary file says so rather than showing you replacement characters, and anything over 512 KB shows its first 512 KB with a note to download the rest — a browser asked to lay out megabytes of text stops responding.

Download this version gives you the exact bytes, named with the version's short hash so two downloads of the same path do not collide.

Restore this version queues a restore (see below).

Pick a second version to diff the two. Selecting another version in the same file turns the pane into a unified diff with additions and removals marked.

5. Restoring

Restore this version queues the restore and asks you to confirm first. What happens next:

1. The restore is queued against that host, for that exact path and version.

A version that is not a real stored version of that host and path is refused outright.

1. The host's agent picks it up on its next check-in.
2. The agent backs up the file as it currently is before overwriting it — so

the restore is itself undoable — then writes the stored version back.

1. The agent acknowledges, and the restore shows as complete.

Restores are recorded. Each host's row carries its recent restores, and the audit log records who asked for what.

6. Comparing across hosts

Compare files across hosts answers the question an operator usually arrives with after an incident: *this box behaves differently — is its config different?*

Pick a path that several hosts have, and Flashback shows you which hosts hold which content for it, grouped so that identical boxes collapse together and the odd one out is obvious. From there you can diff any two of them.

Hosts that have no stored copy of that path are listed separately rather than silently omitted — "this host does not have this file" and "this host has it and it matches" are different answers.

7. Roles

Flashback uses the platform's three roles, asserted by SLOP:

An auditor sees the whole history. What an auditor does not get is the Restore button or the capture buttons, and the API refuses those calls as well as hiding them — the console not showing a control is a convenience, not the enforcement.

8. Retention

Flashback keeps the 50 most recent versions per file by default, set with SYSIBLE_FLASHBACK_KEEP. When a file exceeds that, its oldest versions are pruned and the content they referenced is garbage-collected if no other version still points at it.

Because a version is only written when the content actually changed, 50 versions of a file is 50 real changes to it, not 50 days of an unchanged file. On most configuration this is years of history.

9. Where the data lives

Everything is in the flashback-data Docker volume: the SQLite index and the stored content, de-duplicated by hash so that a file identical across two hundred hosts is stored once.

That volume is the whole product. Back it up — the app can be rebuilt from source in minutes, and the history cannot be rebuilt at all.

10. Security model

• The console is only reachable through the gateway. Flashback's web

interface is not published on a host port; SLOP is the sole front door, and the identity it asserts is checked against the shared secret on every request.

• The agent endpoint is separate and deliberately narrow. Agents post

snapshots to their own port, which is bound to the Docker bridge address rather than to every interface: reachable from this host and from containers on it, not from the network. It is authenticated with its own token (SYSIBLE_FLASHBACK_AGENT_TOKEN), distinct from any operator's session.

• A restore cannot be used to write arbitrary content. It names a host, a path

and a version that Flashback already stores; anything else is refused. You cannot restore a file to a host that never had it, or restore content that was never captured.

• Stored config is treated as hostile input everywhere it is displayed — see

the note under Reading a version.

• Everything that changes a host is audited, with the account that asked.

11. Troubleshooting

No hosts at all. The Controller is not pointed at Flashback, or no agent has checked in yet. The banner at the top of the hosts column says which.

A host is listed but has no files. It has been seen but has not captured yet. Use Back up now on its row and give it one check-in interval.

A file I expect is not there. Flashback stores what the agent was told to capture. The capture set is configured in the Controller, not here.

"No backup captured yet" after pressing Back up now. The request is queued for the agent's next check-in; the console re-reads shortly afterwards. If it persists past a couple of intervals, check that host's agent in the Controller.

A restore was queued but nothing changed. The agent has not checked in, or it has and the service using the file has not been restarted. Check the host's restore activity for the acknowledgement.

12. Reference: environment variables