docs: Add docs for install reset to experimental section

docs/src/SUMMARY.md

@@ -59,6 +59,7 @@
 - [bootc image](experimental-bootc-image.md)
 - [composefs backend](experimental-composefs.md)
 - [fsck](experimental-fsck.md)
+- [install reset](experimental-install-reset.md)
 - [--progress-fd](experimental-progress-fd.md)
 
 # More information

docs/src/experimental-install-reset.md

@@ -0,0 +1,118 @@
+# Factory reset with `bootc install reset`
+
+This is an experimental feature; use `--experimental` flag to acknowledge.
+
+## Overview
+
+The `bootc install reset` command allows you to perform a non-destructive factory reset of an existing bootc system. This creates a fresh installation state in a new stateroot while preserving the existing system's files on disk. After rebooting into the new deployment, you can still access the old system's data by examining files in `/sysroot/ostree/deploy/<old-stateroot>/`.
+
+## How it works
+
+When you run `bootc install reset`:
+
+1. A new stateroot is created with an automatically generated name (format: `state-<year>-<serial>`, e.g., `s2025-0`)
+2. A fresh deployment is created in the new stateroot using the currently booted image (or optionally a different image via `--target-imgref`)
+3. Kernel arguments related to root filesystem configuration are automatically inherited from the current deployment
+4. The `/boot` fstab entry is preserved from the current system if it exists
+5. The new deployment becomes the default boot target
+
+After rebooting, you'll be running in a completely fresh system state:
+- `/etc` contains only the configuration from the container image
+- `/var` is empty (no user data or state from the previous system)
+- The old stateroot's files remain on disk at `/sysroot/ostree/deploy/<old-stateroot>/` and can be accessed for data recovery or inspection
+
+## Usage
+
+Basic usage (reset to the same image currently running):
+
+```bash
+bootc install reset --experimental
+```
+
+Reset and switch to a different image:
+
+```bash
+bootc install reset --experimental --target-imgref quay.io/example/myimage:latest
+```
+
+Reset with custom stateroot name:
+
+```bash
+bootc install reset --experimental --stateroot production-2025
+```
+
+Reset and immediately reboot:
+
+```bash
+bootc install reset --experimental --apply
+```
+
+Add custom kernel arguments:
+
+```bash
+bootc install reset --experimental --karg=console=ttyS0,115200n8
+```
+
+Skip inheriting root filesystem kernel arguments:
+
+```bash
+bootc install reset --experimental --no-root-kargs
+```
+
+## Kernel arguments
+
+By default, `bootc install reset` automatically inherits kernel arguments from the currently booted deployment that are related to root filesystem configuration. This includes:
+
+- `root=` - Root device specification
+- `rootflags=` - Root filesystem mount options
+- `rd.*` arguments - Initramfs arguments (e.g., for LVM, LUKS, network root)
+- Kernel arguments defined in `/usr/lib/bootc/kargs.d/` and `/etc/bootc/kargs.d/`
+
+You can:
+- Add additional kernel arguments with `--karg` (can be specified multiple times)
+- Skip automatic root filesystem argument inheritance with `--no-root-kargs`
+
+## Use cases
+
+- **Development/testing**: Quickly return to a clean state while preserving the ability to boot back to your development environment
+- **Troubleshooting**: Reset to a known-good state without losing access to the problematic deployment for debugging
+- **System refresh**: Start fresh after accumulating configuration changes, while keeping the old state accessible
+- **Image testing**: Test a new image version in a separate stateroot before committing to it
+
+## Cleaning up the old stateroot
+
+After performing a factory reset and rebooting into the new stateroot, the old stateroot remains on disk at `/sysroot/ostree/deploy/<old-stateroot>/`. This allows you to access files from the previous system if needed.
+
+Once you no longer need the old stateroot, you can remove it to free up disk space:
+
+1. First, remove any remaining deployments from the old stateroot:
+
+```bash
+# List all deployments to find the old stateroot's deployment index
+ostree admin status
+
+# Remove the old deployment(s) by index
+# The index is shown in the output (e.g., "1" for the second deployment)
+ostree admin undeploy <index>
+```
+
+2. After all deployments from the old stateroot are removed, you can delete the stateroot directory:
+
+```bash
+# Replace "default" with your old stateroot name if different
+mount -o remount,rw /sysroot
+rm -rf /sysroot/ostree/deploy/default
+```
+
+**Note:** You cannot remove the stateroot directory while deployments still exist in it. OSTree protects deployment directories with filesystem-level mechanisms, so you must undeploy them first using `ostree admin undeploy`.
+
+## Limitations
+
+- This command requires `--experimental` flag as the feature is still under development
+- Only works on systems already running bootc (not for initial installations)
+- The old stateroot is not automatically removed and will consume disk space until manually deleted (see "Cleaning up the old stateroot" section above)
+
+## See also
+
+- `bootc switch` - Switch to a different container image
+- `bootc status` - View current deployment status