Overlay Images To the Rescue
summary
Yocto images break the rootfs into composable layers and the talk shows a working workflow that uses systemd-sysext (systemd 248) plus overlayfs and btrfs subvolumes to load and unload squashfs extension images at runtime. Examples include loading prebuilt debug symbols and launching gdbserver, enabling bpftrace (LLVM/BCC deps), and deploying tailscale as an extension. A reproducible builder is demonstrated via an Avocado SDK container and Kimu emulator creating runnable squashfs raw images.
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chapters (17)
- 0:00Introduction to overlay images and the talk agenda
- 1:04What is an immutable Linux distribution
- 5:53Steam Deck's immutable Linux architecture
- 8:48Origin of capsule images and their purpose
- 10:58Systemd extension images explained
- 13:29Why choose extension images over containers
- 15:14Deploying extension images on Steam Deck
- 18:48Building an SSHD extension image step by step
- 21:38Native GDB debugging with extension images
- 23:50Remote GDB debugging workflow with SDK container
- 27:49Adding BPF trace for observability via extensions
- 30:07Deploying Tail Scale VPN as a system extension
- 31:36Systemd auto-reload feature for extensions
- 35:11Addressing YOTO pain points with Avocado Linux
- 36:19Introducing Avocado Linux and its SDK
- 38:54Book promotion and author credits
- 40:17Q&A on immutable systems and extension images
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