b4n

b4n is a terminal user interface (TUI) for the Kubernetes API, created mainly for learning the Rust programming language. It is heavily based on the k9s project and built using the kube-rs and ratatui crates.

Prerequisites

The Cascadia Code font, or any other font with Nerd Font symbols, is required for proper display of the user interface in the terminal.

Building

To build b4n ensure you have a recent Rust toolchain installed (1.88+ recommended). Clone the repository and navigate into the project directory:

git clone https://github.com/fioletoven/b4n.git
cd b4n

Then compile the project in release mode for optimal performance:

cargo build --release

The resulting binary will be available at ./target/release/b4n.

Features

Currently Supported

The following features are currently supported:

• View and filter a list of Kubernetes resources.
• Create, read, update, and delete Kubernetes resources.
• View events for the highlighted resource.
• View logs for the highlighted pod or container.
• Open a shell session or attach to the highlighted container's main process.
• Enable port forwarding for the highlighted container.
• Mouse support in all views.

Planned

The following features are planned for future development:

• File transfer from/to a pod.
• Custom commands (simple plugin system to run external binaries).
• Describe Kubernetes resources.

Default Key Bindings

Action	Command	Comments
Attach to the container's main process	a	Works only in containers view
Attach to the container's shell	s	Works only in containers view
Copy YAML / logs / resources to clipboard	c	Works only in YAML, logs and resources views
Create new resource	n
Decode highlighted secret	x
Delete selected resources	CTRL + d	Displays a confirmation dialog
Enable / disable mouse support	CTRL + n	Not available inside a shell session
Forward container's port	f	Works only in containers view
Go back to namespaces; clear filter	ESC	Also clears input in the filter widget
Navigate to the involved object	i	Works only for events kind
Open / switch to edit mode	i	Press ESC to exit, then ESC for save dialog
Open right mouse button menu	m	Navigate using ↑ or ↓
Pin active filter across resources	CTRL + p	Also works in the filter dialog
Quit the application	CTRL + c	No confirmation dialog
Reverse selection	CTRL +	(CTRL + SPACE)
Select resource		(SPACE)
Show / hide log timestamps	t	Works only in logs view
Show / hide port forwards	CTRL + f	Displays all active port forwarding rules
Show command palette	:, >	For example, entering :q↲ quits the application
Show events for the highlighted resource	e
Show filter / search input	/	Filter operators: and &, or |, negation !, (, )
Show footer messages history pane	h	Also works with left mouse button click on the footer
Show logs for the pod or container	l	Press p to display previous logs
Show namespaces selector	←	To select all rapidly press ← again
Show resources selector	→	To select pods rapidly press → again
Show YAML for the highlighted resource	y
Sort column	ALT + [0-9]	Also works with ALT + [underlined letter]

Advanced Filtering

The resources and port forwards views support advanced filtering with prefixes:

• ns: - filter by namespace (e.g., ns:kube-system)
• n: - filter by resource name (e.g., n:nginx)
• a: - filter by annotations (e.g., a:app.kubernetes.io/name=nginx)
• l: - filter by labels (e.g., l:app=frontend)

Filters can be combined using logical operators: & (and), | (or), ! (negation), and parentheses ().

Example: ns:default & (l:app=web | l:app=api)

Note: CTRL + p will pin the active filter across resource changes

Logs View

When viewing logs for a single container, you can fetch earlier log entries by pressing the ↑ (up arrow) key. This feature is only available when you are scrolled to the top of the currently displayed logs and there are additional log entries available before the first visible line.

Note: This functionality works only in single container logs view, not when viewing combined logs for all containers in a pod.

Text Selection and Editing

When mouse support is enabled, you can:

• Select text by clicking and dragging in YAML, logs, shell, and attach view
• Select whole words by double-clicking
• Select whole lines by triple-clicking
• Copy selected text to clipboard using standard key bindings

In edit mode, the following shortcuts are available:

• CTRL + c - copy selected text
• CTRL + x - cut selected text
• CTRL + v - paste text from clipboard
• CTRL + a - select all text
• CTRL + d - delete current line
• CTRL + z - undo
• CTRL + y - redo
• ALT + ↑ - move current line up
• ALT + ↓ - move current line down

Note: These shortcuts currently cannot be changed in the key_bindings configuration section

Configuration Files

Configuration files are stored in the $HOME/.b4n directory. The directory structure is as follows:

.b4n/
├─ logs/
├─ themes/
│  └─ default.yaml
├─ config.yaml
└─ history.yaml

logs/

This directory contains application logs, with one log file generated per day.

themes/

This folder stores all TUI (Text User Interface) themes.
The default.yaml theme will be automatically generated by the application if it doesn't already exist.

You can place additional theme files here by copying them from the themes folder or creating your own.

config.yaml

This file contains configuration settings that control the behaviour of the b4n application.
Here is an example structure:

logs:
  lines: 800
  timestamps: true
mouse: true
theme: light
contexts:
  test-cluster: '#43464f:#8aad81'
  production: '#d8d8d8:#e1140a'
aliases:
  daemonsets: ds,dms
  namespace: nn
  namespaces: ns,na,nam
  services: svc
key_bindings:
  action.name: list of key bindings for that action
  command-palette.open: :, >, Shift+:, Shift+>
  [...]

Configuration Options

• logs.lines - The number of log lines to retrieve from the Kubernetes API for the selected container.
• logs.timestamps - Indicates whether timestamps are enabled by default for logs; this setting can still be toggled while viewing the logs.
• mouse - Indicates if mouse support should be enabled when the application starts. Mouse support can also be toggled while the app is running.
• theme - The name of the currently selected theme. This should match a file in the themes directory (without the .yaml extension).
• contexts - (Optional) A map of context names to their corresponding colors. Useful for highlighting important Kubernetes clusters with distinct header colors.
• aliases - Command palette aliases.
• key_bindings - Defines custom key bindings for various application actions.
  Example key bindings: Ctrl+C, Ctrl+Alt+A, F7, Z, Left, Enter.

Note: If config.yaml does not exist, the application will create it automatically with default values.

history.yaml

This file stores history for filters, search patterns, and the last selected resource for each Kubernetes context. To remove history entries (either for a specific context or entirely), you can manually edit this file or even delete it.
History entries can also be deleted from the UI, just highlight one and press Ctrl+D to delete it.

License

MIT