A real Linux boundary
Run an independent kernel in KVM, install normal packages, and use an unmodified ext4 filesystem. The Guest never receives platform storage credentials.
Durable cloud workspaces
Your Linux workspace, ready when you are.
Cats gives every workspace a real Linux microVM with durable disks and a stable identity. Work at full speed, let it sleep when idle, and wake it without rebuilding your environment.
True pay-as-you-go
Durable data by default
Linux ready on demand
dev-workspaceubuntu-24.04 · 2 CPU · 2 GiB$ cats login signed in · workspace acme-dev $ cats create dev creating durable RootDisk… starting guest… ready $ cats exec dev -- git status On branch main nothing to commit, working tree clean idle → suspended · work preserved
ActiveRunning
Fast wakeSuspended
Local snapshotWarm
Zero computeCold
One durable environment
Keep the machine. Release the compute.
A Cat is a long-lived Linux microVM, not a disposable container session. Its name and disk outlive any one host.
Sleep without starting over
Running, Suspended, Warm, and Cold are distinct states. Fast host-bound resume is available, and every failed fast restore converges to a clean Cold start.
Disks that survive hosts
Successful FLUSH operations publish to durable remote storage. Local NVMe is a cache, while fencing keeps every PersistentDisk single-writer in V1.
Lifecycle, made explicit
Four states. No vague “sleep” mode.
Choose the right balance between wake speed, preserved process state, and complete host independence.
Running
vCPU executes, memory is resident, disks keep publishing durable generations, and endpoints can serve traffic.
Full computeSuspended
vCPUs pause and process state stays on the original host. The VMM and host affinity remain for the shortest resume path.
Process state keptWarm
The VMM exits after a host-local snapshot. Runtime RSS becomes zero, but restore still uses the original healthy host.
Local snapshotCold
All host runtime resources are released. A new host can boot from the last durable disk generation.
Host independentDurability contract
Your disk is the truth. The host is replaceable.
Cats keeps the user-facing promise narrow and testable: a successful durable FLUSH survives permanent host loss.
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Standard block devices
The Guest sees virtio block devices and ordinary ext4—never object-store APIs or metadata credentials.
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Small writes stay small
The block engine tracks dirty logical chunks. It does not upload an entire sparse virtual disk to commit a small working set.
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Old writers fail closed
Every attachment has a fencing epoch. A host that returns after a partition cannot publish over a newer writer.
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PersistentDisk is independent
Destroying a Cat removes its RootDisk; a detached PersistentDisk remains available until you explicitly delete it.
Start with one Cat.
Follow the quickstart, create a durable workspace, run a command, and understand exactly what happens when it sleeps.