b4n

b4n is a terminal user interface (TUI) for the Kubernetes API, created mainly for learning the Rust programming language. It is heavily inspired by 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 (1.95+). 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 the best performance:

cargo build --release

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

Features

• 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.
• Inject an ephemeral container into the highlighted pod.
• Transfer files to and from containers (requires tar executable on the container).
• Run external binaries configured in a simple plugin system.
• Support mouse interactions in all views.

Default Key Bindings

Action	Command	Comments
Attach to the container's main process	a	Works only in containers and pods view
Attach to the container's shell	s	Works only in containers and pods 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 and pods view
Go back to namespace view; clear filter	ESC	Also clears input in the filter widget
Inject ephemeral container	CTRL + i	Works only in pods view, displays a confirmation dialog
Navigate to the involved object	i	Works only for events kind
Open / enter 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)
Save YAML / logs to a file	s
Select all resources	CTRL + a	Then press CTRL +   to deselect all
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 describe for the highlighted resource	d
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]
Transfer file from the pod's container	CTRL + t	Allows downloading a single file or a directory
Transfer file to the pod's container	t	Allows uploading only a single file

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 keeps the active filter pinned when you switch resources.

Logs View

When viewing logs for a single container, you can fetch earlier entries by pressing ↑ (up arrow). This works only when you are already scrolled to the top of the current log output and earlier entries are still available.

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 the YAML, logs, shell, and attach views
• 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

File Transfer

Feature requires a tar executable on the container where files are uploaded to or downloaded from.

If Overwrite files is unchecked before the transfer, a check will be executed on the remote container that requires the presence of sh and test commands (if the container does not have these commands, as a workaround the checkbox can be checked, but be aware that files may be overwritten).

If the destination path (To (dir): textbox) contains ~, there will be an attempt to resolve it to the home directory (this requires sh and echo commands to be present on the container). To bypass this, simply provide the full path without ~.

Note: Currently, the upload feature supports only uploading a single file.

Configuration Files

Configuration files are stored in platform-specific directories. The exact paths depend on your operating system:

Windows

%LOCALAPPDATA%\b4n\config\config.yaml
%LOCALAPPDATA%\b4n\data\history.yaml

Example: C:\Users\<user>\AppData\Local\b4n\

macOS

~/Library/Application Support/b4n/config/config.yaml
~/Library/Application Support/b4n/data/history.yaml

Linux

~/.config/b4n/config.yaml
~/.local/share/b4n/history.yaml

Note: If the platform-specific directories cannot be determined, b4n falls back to $HOME/.b4n/.
To list paths expected by the application: b4n --show-dirs

The layout is as follows:

<config_dir>/
└─ config.yaml
<data_dir>/
├─ logs/
├─ plugins/
├─ themes/
└─ history.yaml

logs/

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

plugins/

This folder contains custom command definitions that appear in the command palette in the resources view (the main b4n screen). Store each command in a separate .yaml file.

name: plugin-name
aliases: []          # additional aliases recognised by the command palette
description: "plugin description"
shortcut: Ctrl+Y
command: dive
args: []             # command arguments; see the available variables below
scopes:
  - pods             # scopes where the plugin will be visible; empty means all (format: 'plural[.group/version]')
excluded_scopes: []  # scopes where the plugin will be hidden; empty means none
inputs:              # list of inputs to show in the modal dialog before plugin run
  - name: name       # used in $INPUT[] placeholders to get input's value (in this case $INPUT[NAME])
    kind: checkbox   # type of the input: `checkbox`, `textbox` or `select`
    label: caption   # caption for the input
    value: text      # initial value for the input
    options: []      # array of possible options (used only in `select` and `checkbox` inputs)
    required: false  # requires user to provide a value (used only in `textbox` input)
confirm: false       # show run confirmation dialog
interactive: true    # run the command as an interactive terminal application; otherwise run it in the background
keep_output: false   # do not close terminal on command exit
keep_error: true     # do not close terminal if command exited with error (if keep_output: false)
output_type: plain   # highlight output as `plain`, `yaml` or `describe` (if keep_output: true and interactive: false)
auto_mouse: false    # automatically enable mouse support if app asks for it
pin_to_top: false    # stay at the beginning of the command output
highlighted: true    # allow running the plugin only when a resource in the list is highlighted
selected: false      # allow running the plugin only when at least one resource is selected
for_each: false      # run each selected resource separately (if interactive: false)

Variable name	Description
$CONTEXT	currently selected kubeconfig context
$PLURAL	plural name of the displayed resource kind
$GROUP	displayed resource group
$VERSION	displayed resource version
$NAMESPACE	currently selected namespace
$RES[NAME]	name of the highlighted or selected resource
$RES[NAMESPACE]	namespace of the highlighted or selected resource
$RES[UID]	UID of the highlighted or selected resource
$RES[CONTAINER]	container name of the highlighted or selected resource (pods only)
$COL[COLUMN_NAME]	any visible column value from the highlighted or selected resource
$INPUT[NAME]	input's value provided by the user

The plugins folder is not created automatically. Example plugins are available in the assets/plugins folder.

themes/

This folder stores TUI themes. It is not created automatically. Place theme files here to make them available in the application - either by copying themes from the assets/themes folder or by creating your own.

config.yaml

This file contains settings that control how b4n behaves.
Example structure:

logs:
  lines: 800
  timestamps: true
mouse: true
terminal:
  system_cursor: false
  scrollback_lines: 1000
theme: light
debug_images:
- busybox
- alpine
- nicolaka/netshoot
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 - Number of log lines to retrieve from the Kubernetes API for the selected container.
• logs.timestamps - Whether timestamps are enabled by default for logs. You can still toggle this while viewing logs.
• mouse - Whether mouse support is enabled when the application starts. You can also toggle it while the app is running.
• terminal.system_cursor - If true all terminal views will stop drawing its own cursor and start using the system one.
• terminal.scrollback_lines - A configurable maximum size limit of the terminal scrollback buffer.
• theme - The name of the currently selected theme. This should match a file in the themes directory (without the .yaml extension).
• debug_images - List of container images that are displayed during ephemeral container injection.
• 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 the history for filters, search patterns, and the last selected resource for each Kubernetes context. To remove entries for a specific context, or to clear the file entirely, you can edit or delete it manually.
You can also delete history entries from the UI by highlighting one and pressing Ctrl+D.

Screenshots

License

MIT