Setting Up Dev Tools on Ubuntu - llama.cpp, Slack, Git and JupyterLab

A practical walkthrough of setting up a local AI development environment on Ubuntu — covering llama.cpp installation via Homebrew, running local LLMs with LangChain, fixing common Slack conflicts, Git branch management, and JupyterLab. Hard-won lessons from real terminal errors.

Installing llama.cpp via Homebrew on Ubuntu

Homebrew on Linux — Homebrew is primarily a macOS package manager but works on Linux too. Install it with the official script and add it to your PATH via ~/.zshrc using eval "$(/home/linuxbrew/.linuxbrew/bin/brew shellenv)".

brew install llama.cpp — Installs llama.cpp and its dependencies including ggml (the tensor/ML backend) and openssl@3. The binaries land in /home/linuxbrew/.linuxbrew/bin/ and won't be accessible until Homebrew is added to PATH.

PATH fix is mandatory — After install, running llama-cli gives command not found because /home/linuxbrew/.linuxbrew/bin/ is not in PATH by default. Add eval "$(/home/linuxbrew/.linuxbrew/bin/brew shellenv)" to ~/.zshrc and source it.

Available binaries — llama.cpp ships with 35+ tools including llama-cli (inference), llama-server (OpenAI-compatible REST API), llama-bench (benchmarking), llama-quantize (model quantization), llama-tts (text-to-speech), and llama-diffusion-cli (diffusion models).

Running Local LLMs with llama-server and LangChain

llama-server — Starts a local OpenAI-compatible REST API server on localhost:8080. Point any OpenAI SDK or LangChain app at it by setting BASE_URL=http://localhost:8080/v1 in your .env file.

LangChain + ChatOpenAI — LangChain's ChatOpenAI class works with local llama-server by overriding base_url. The api_key is just a placeholder — llama.cpp doesn't validate it. Temperature range is 0.0 to 2.0; setting it to 5 causes gibberish or errors.

GGUF models are required — llama-server needs a real .gguf model file. Download models via huggingface-cli download. Good starter models: Phi-3.5-mini-Q4 (~2.2GB for 4GB RAM), Mistral-7B-Q4 (~4.1GB for 16GB RAM).

Port conflict fix — If llama-server fails with couldn't bind HTTP server socket, port 8080 is already in use. Use sudo lsof -i :8080 to find the process and sudo kill -9 <PID> to free it, or start the server on a different port with --port 8081.

lsof -i explained — lsof means "List Open Files." The -i flag filters results to show only internet/network connections. lsof -i :8080 shows exactly which process is occupying a specific port.

The Slack Name Conflict on Ubuntu

Two different programs named slack — Ubuntu has a sysadmin configuration management tool called slack at /usr/sbin/slack. It tries to rsync config from a server called slack-master and fails with a DNS error. This is NOT the Slack chat app.

snap install is the cleanest route — sudo snap install slack installs Slack chat app version 4.49.81 to /snap/bin/slack. Always launch via snap run slack or add /snap/bin before /usr/sbin in PATH to avoid calling the wrong binary.

Outdated versions get blocked — Slack versions older than a certain threshold show "This version of the app is no longer supported." The .deb at version 4.38 or 4.40 will be blocked on login. Use snap for the latest version automatically.

deb conflict with sysadmin slack — Installing slack-desktop via .deb fails with trying to overwrite '/usr/share/lintian/overrides/slack' because the sysadmin slack package owns that file. Fix with sudo dpkg -i --force-overwrite followed by sudo apt install -f.

Git Branch Management

git init before anything — Running git add or git status outside a Git repo gives fatal: not a git repository. Always run git init first in the project root.

Nested .git folders break git add — If a subfolder has its own .git directory, Git treats it as a submodule and refuses to add it: error: 'folder/' does not have a commit checked out. Fix by removing the nested .git with rm -rf subfolder/.git.

master vs main mismatch — Git still defaults to master as the initial branch name. GitHub defaults to main. Push fails with src refspec main does not match any if you push to the wrong branch name. Fix: git branch -m master main then git push -u origin main.

--set-upstream explained — When you create a new local branch, Git doesn't know where to push it. git push --set-upstream origin branch-name (or -u) creates the branch on GitHub and links the local branch to track it. After that, plain git push works with no extra flags.

--set-upstream vs --set-remote — These are different. --set-remote changes which server (GitHub vs GitLab) a branch points to. --set-upstream links a local branch to a specific branch on a remote server. Remote = the post office. Upstream = the specific PO box.

JupyterLab and Conda

jupyter lab not python lab — The correct command to launch JupyterLab is jupyter lab, not python lab or pythonlab. It opens a browser interface at http://localhost:8888 automatically.

conda activate first — Always run conda activate <env-name> before launching JupyterLab to ensure the correct Python environment and installed packages are used inside notebooks.

Ubuntu Dock and Font Customization

Move dock to horizontal — Go to Settings → Appearance → Dock → Position on screen → Bottom. Or via terminal: gsettings set org.gnome.shell.extensions.dash-to-dock dock-position BOTTOM.

Increase font size — Settings → Accessibility → Large Text toggle, or install gnome-tweaks (sudo apt install gnome-tweaks) and adjust Fonts → Scaling Factor. Terminal shortcut: gsettings set org.gnome.desktop.interface text-scaling-factor 1.5. Valid range is 1.0 (default) to 2.0.