blog: Add GSoC'25 expanding catalog, Part I post

content/blog/2025-06-25-expanding-catalog.mdx

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+---
+title: "GSoC'25: Expanding the Unikraft Software Support Ecosystem"
+description: |
+  This GSoC project aims to expand Unikraft’s software support by adding new applications via binary-compatibility mode into the application catalog.
+publishedDate: 2025-06-25
+image: /images/gsoc25.jpeg
+authors:
+- Prasoon Kumar
+tags:
+- gsoc
+- gsoc25
+- catalog
+- sqlite
+- mosquitto
+- prometheus
+- consul
+---
+
+## Project Overview
+
+Unikraft makes it easy to run existing applications in two ways:
+1. **Musl libc support**
+
+2. [**Binary-compatibility mode**](https://unikraft.org/docs/concepts/compatibility):
+Unikraft can run unmodified Linux ELF binaries by using an ELF loader app and a system-call shim layer.
+When a binary-compatible unikernel starts, the `app-elfloader` parses and maps the ELF segments into memory, then transfers control to the application entry point.
+Whenever the application invokes a Linux system call, the syscall shim intercepts the call number and routes it to the corresponding Unikraft handler.
+Unimplemented calls return `ENOSYS`, which many applications can handle or fake because Unikraft follows Linux’s x86_64 ABI closely.
+This helps when running on hypervisors like KVM, QEMU, or Firecracker.
+
+## Adding an application in binary-compatibility mode
+
+Though the full procedure is detailed in the Unikraft Docs (see [Adding Applications to the Catalog](https://unikraft.org/docs/contributing/adding-to-the-app-catalog)), here are a few additional findings:
+
+1. **Find supported syscalls**
+    - Search for syscall macros in the Unikraft source (see [Syscall Shim Layer](https://unikraft.org/docs/internals/syscall-shim)).
+    - Or look for `UK_PROVIDED_SYSCALLS-` entries in the `Makefile.uk` files of Unikraft libraries.
+2. **Discover the application’s syscalls**
+    - Run the application under `strace` inside a container using `strace -o {destination_file} -f {application_binary}`.
+    - Save the trace output and extract the unique syscall list using `awk '{split($2, a, "("); print a[1]}' strace_out.txt | sort | uniq`.
+    - Compare against Unikraft’s supported syscalls set, to spot any missing calls.
+3. **Prepare a dynamic ELF**
+    - If the existing Docker image has only a statically linked binary, rebuild the application in an `alpine` container to produce a `PIE (ET_DYN)` ELF suitable for Unikraft’s loader.
+
+## Current Progress
+
+Initially, I selected a subset of 14 applications and listed out the system calls they use which are not yet supported in Unikraft.
+
+I looked for adding the following applications in the [catalog](https://github.com/unikraft/catalog) in binary-compatibility mode and I was able to add several of them.
+I'm also looking into finding and documenting the reasons why some applications can't be added to bincompat yet:
+
+1. **sqlite:3.44**
+    - A small, serverless SQL database engine that stores data in a single file, perfect for edge and cloud applications needing fast, local storage without a separate server.
+    - Runs successfully once `CONFIG_LIBPOSIX_PROCESS_SIGNAL` is enabled in the Kraftfile.
+    - Initially, I opened a PR before GSoC, but have later discovered that the POSIX process signal option was required.
+    - Added GitHub Actions workflow YAML in the catalog for automatic builds.
+    - Pull Request: [catalog#163](https://github.com/unikraft/catalog/pull/163).
+
+2. **mosquitto:2.0.21**
+    - A lightweight MQTT message broker used in microservice systems, enabling efficient, real-time publish / subscribe communication.
+    - Unikraft currently lacks multi-user support, so the user must be hard-coded as root in `mosquitto.conf`.
+    - Added GitHub Actions workflow YAML in the catalog for automatic builds.
+    - Pull request: [catalog#207](https://github.com/unikraft/catalog/pull/207)
+
+3. **prometheus:2.53.4**
+    - A monitoring and alerting system for cloud-native environments, collecting and querying metrics to help operators observe and maintain distributed services.
+    - Uses file-backed `mmap(..., MAP_SHARED, ...)`, which is not yet supported in Unikraft.
+
+4. **consul:1.21.1**
+    - A service discovery and configuration platform that enables dynamic registration, health checks, and key / value storage for microservice orchestration.
+    - Calls `socket(AF_NETLINK, ...)`, which Unikraft does not support yet.
+
+## Next Steps
+
+For the next three weeks, I plan to continue expanding the catalog by adding more high-priority applications.
+My immediate targets are:
+- **etcd**: A distributed key-value store for service discovery and coordination in cloud-native environments.
+- **InfluxDB**: A time-series database optimized for real-time monitoring and analytics.
+- **Vault**: A tool for securely managing secrets and encryption keys.
+
+I will follow the binary-compatibility workflow as I discussed [above](/blog/2025-06-25-expanding-catalog#adding-an-application-in-binary-compatibility-mode).
+
+## Acknowledgement
+
+I would like to thank my mentors, [Razvan Virtan](https://github.com/razvanvirtan) and [Razvan Deaconescu](https://github.com/razvand), for their guidance throughout this project.
+I’m also grateful to the entire Unikraft community for being so welcoming and helpful.
+
+## About Me
+
+I am a first-year MTech student at IIT Bombay.
+I have experience across many areas of computer science, including operating systems, virtualization, Web3, web development, and algorithms.
+In my free time, I love solving challenging math and algorithmic problems.
+- Socials: [Linkedin](https://www.linkedin.com/in/prasoon054/)  [Twitter](https://x.com/prasoon054) [Github](https://github.com/prasoon054)