kmon

Linux Kernel Manager and Activity Monitor 🐧💻

View the Project on GitHub orhun/kmon


Linux Kernel Manager and Activity Monitor 🐧💻


The kernel is the part of the operating system that facilitates interactions between hardware and software components. On most systems, it is loaded on startup after the bootloader and handles I/O requests as well as peripherals like keyboards, monitors, network adapters, and speakers. Typically, the kernel is responsible for memory management, process management, device management, system calls, and security. Applications use the system call mechanism for requesting a service from the operating system and most of the time, this request is passed to the kernel using a library provided by the operating system to invoke the related kernel function. While the kernel performs these low-level tasks, it’s resident on a separate part of memory named protected kernel space which is not accessible by applications and other parts of the system. In contrast, applications like browsers, text editors, window managers or audio/video players use a different separate area of the memory, user space. This separation prevents user data and kernel data from interfering with each other and causing instability and slowness, as well as preventing malfunctioning application programs from crashing the entire operating system.
There are different kernel designs due to the different ways of managing system calls and resources. For example, while monolithic kernels run all the operating system instructions in the same address space for speed, microkernels use different spaces for user and kernel services for modularity. Apart from those, there are hybrid kernels, nanokernels, and, exokernels. The hybrid kernel architecture is based on combining aspects of microkernel and monolithic kernels.

The Linux kernel is the open-source, monolithic and, Unix-like operating system kernel that used in the Linux distributions, various embedded systems such as routers and as well as in the all Android-based systems. Linus Torvalds conceived and created the Linux kernel in 1991 and it’s still being developed by thousands of developers today. It’s a prominent example of free and open source software and it’s used in other free software projects, notably the GNU operating system. Although the Linux-based operating systems dominate the most of computing, it still carries some of the design flaws which were quite a bit of debate in the early days of Linux. For example, it has the largest footprint and the most complexity over the other types of kernels. But it’s a design feature that monolithic kernels inherent to have. These kind of design issues led developers to add new features and mechanisms to the Linux kernel which other kernels don’t have.

Unlike the standard monolithic kernels, the Linux kernel is also modular, accepting loadable kernel modules (LKM) that typically used to add support for new hardware (as device drivers) and/or filesystems, or for adding system calls. Since LKMs could be loaded and unloaded to the system at runtime, they have the advantage of extending the kernel without rebooting and re-compiling. Thus, the kernel functionalities provided by modules would not reside in memory without being used and the related module can be unloaded in order to free memory and other resources.
Loadable kernel modules are located in /lib/modules with the .ko (kernel object) extension in Linux. While the lsmod command could be used for listing the loaded kernel modules, modprobe or insmod/rmmod is used for loading or unloading a kernel module. insmod/rmmod are used for modules independent of modprobe and without requiring an installation to /lib/modules/$(uname -r).

Here’s a simple example of a Linux kernel module that prints a message when it’s loaded and unloaded. The build and installation steps of the module using a Makefile are shown below.

make                         # build
sudo make install            # install
sudo modprobe lkm_example    # load
sudo modprobe -r lkm_example # unload

The dmesg command is used below to retrieve the message buffer of the kernel.

[16994.295552] [+] Example kernel module loaded.
[16996.325674] [-] Example kernel module unloaded.

kmon provides a text-based user interface for managing the Linux kernel modules and monitoring the kernel activities. By managing, it means loading, unloading, blacklisting and showing the information of a module. These updates in the kernel modules, logs about the hardware and other kernel messages can be tracked with the real-time activity monitor in kmon. Since the usage of different tools like dmesg and kmod are required for these tasks in Linux, kmon aims to gather them in a single terminal window and facilitate the usage as much as possible while keeping the functionality.

kmon is written in Rust and uses tui-rs & termion libraries for its text-based user interface.

Table of Contents

Installation

Packaging status

Cargo

kmon can be installed from crates.io using Cargo if Rust is installed.

cargo install kmon

Use the --force option to update.

cargo install kmon --force

Arch Linux

kmon can be installed from the Arch Linux official repository.

pacman -S kmon

There are also a development package on AUR. Use your favorite AUR helper to install. For example,

yay -S kmon-git

Nixpkgs

kmon can be installed using Nix package manager from nixpkgs-unstable channel.

nix-channel --add https://nixos.org/channels/nixpkgs-unstable
nix-channel --update nixpkgs
nix-env -iA nixpkgs.kmon

On NixOS:

nix-channel --add https://nixos.org/channels/nixos-unstable
nix-channel --update nixos
nix-env -iA nixos.kmon

Docker

Docker Hub Build Status Package Registry Build Status

docker run -it --cap-add syslog orhunp/kmon:tagname

Build

docker build -t kmon .

Run

docker run -it --cap-add syslog kmon

Manual

  1. Download the latest binary from releases.
wget https://github.com/orhun/kmon/releases/download/v[VERSION]/kmon-[VERSION].tar.gz
  1. Extract the files.
tar -xvzf kmon-*.tar.gz
  1. Run the binary.
./kmon
  1. Move binary to /usr/local/bin/ for running it from the terminal using kmon command.

  2. Man page could be viewed if kmon.8 file is copied to /usr/local/man/man8/ directory.

cp kmon.8 /usr/local/man/man8/
gzip /usr/local/man/man8/kmon.8
man kmon

Note

libxcb should be installed for using the copy/paste commands of X11. *

e.g: Install libxcb1-dev package for Debian/Ubuntu* and libxcb-devel package for Fedora/openSUSE/Void Linux.

Usage

kmon [FLAGS] [OPTIONS] [SUBCOMMANDS]

Flags

-h, --help       Prints help information
-r, --reverse    Reverse the kernel module list
-u, --unicode    Show Unicode symbols for the block titles
-V, --version    Prints version information

Options

-a, --accent-color <COLOR>    Set the accent color using hex or color name [default: white]
-c, --color <COLOR>           Set the main color using hex or color name [default: darkgray]
-t, --tickrate <MS>           Set the refresh rate of the terminal [default: 250]

Subcommands

help    Prints this message or the help of the given subcommand(s)
sort    Sort kernel modules
kmon sort [FLAGS]

FLAGS:
    -n, --name         Sort modules by their names
    -s, --size         Sort modules by their sizes
    -d, --dependent    Sort modules by their dependent modules

Key Bindings

   
[?], F1 Help
right/left, h/l Switch between blocks
up/down, k/j, alt-k/j Scroll up/down [selected block]
pgup/pgdown Scroll up/down [kernel activities]
</> Scroll up/down [module information]
alt-h/l Scroll right/left [kernel activities]
ctrl-t/b, home/end Scroll to top/bottom [module list]
alt-e/s Expand/shrink the selected block
ctrl-x Change the block position
ctrl-l/u, alt-c Clear the kernel ring buffer
[d], alt-d Show the dependent modules
[1]..[9] Jump to the dependent module
[\], tab, backtab Show the next kernel information
[/], s, enter Search a kernel module
[+], i, insert Load a kernel module
[-], u, backspace Unload the kernel module
[x], b, delete Blacklist the kernel module
ctrl-r, alt-r Reload the kernel module
y/n Execute/cancel the command
c/v Copy/paste
r, F5 Refresh
q, ctrl-c/d, ESC Quit

Features

Help

Press ‘?’ while running the terminal UI to see key bindings.

Help

Arrow keys are used for navigating between blocks and scrolling.

Navigating & Scrolling

Scrolling Kernel Activities

Some kernel messages might be long enough for not fitting into the kernel activities block since they are not wrapped. In this situation, kernel activities can be scrolled horizontally with alt-h & alt-l keys. Vertical scrolling mechanism is the same as other blocks.

Scrolling Kernel Activities

Smooth Scrolling

alt-j & alt-k keys can be used to scroll kernel activity and module information blocks slowly.

Smooth Scrolling

Block Sizes

alt-e & alt-s keys can be used for expanding/shrinking the selected block.

Block Sizes

Block Positions

ctrl-x key can be used for changing the positions of blocks.

Block Positions

Kernel Information

Use one of the \, tab, backtab keys to switch between kernel release, version and platform informations.

Kernel Information

Module Information

The status of a kernel module is shown on selection.

Module Information

Displaying the dependent modules

Use one of the d, alt-d keys to show all the dependent modules of the selected module.

Displaying the dependent modules

Jumping to dependent modules

For jumping to a dependent kernel module from its parent module, number keys (1-9) can be used for specifying the index of the module on the Used By column.

Dependency Information

Searching a module

Switch to the search area with arrow keys or using one of the /, s, enter and provide a search query for the module name.

Searching a module

Loading a module

For adding a module to the Linux kernel, switch to load mode with one of the +, i, insert keys and provide the name of the module to load. Then confirm/cancel the execution of the load command with y/n.

Loading a module

The command that used for loading a module:

modprobe <module_name> || insmod <module_name>.ko

Unloading a module

Use one of the -, u, backspace keys to remove the selected module from the Linux kernel.

Unloading a module

The command that used for removing a module:

modprobe -r <module_name> || rmmod <module_name>

Blacklisting a module

Blacklisting is a mechanism to prevent the kernel module from loading. To blacklist the selected module, use one of the x, b, delete keys and confirm the execution.

Blacklisting a module

The command that used for blacklisting a module:

if ! grep -q <module_name> /etc/modprobe.d/blacklist.conf; then
  echo 'blacklist <module_name>' >> /etc/modprobe.d/blacklist.conf
  echo 'install <module_name> /bin/false' >> /etc/modprobe.d/blacklist.conf
fi

Reloading a module

Use ctrl-r or alt-r key for reloading the selected module.

Reloading a module

The command that used for reloading a module:

modprobe -r <module_name> || rmmod <module_name> && modprobe <module_name> || insmod <module_name>.ko

Clearing the ring buffer

The kernel ring buffer can be cleared with using one of the ctrl-l/u, alt-c keys.

Clearing the ring buffer

dmesg --clear

Copy & Paste

c/v keys are set for copy/paste operations.

Copy & Paste

Use ctrl-c/ctrl-v for copying and pasting while in input mode.

Sorting/reversing the kernel modules

sort subcommand can be used for sorting the kernel modules by their names, sizes or dependent modules.

kmon sort --name
kmon sort --size
kmon sort --dependent

Sorting the kernel modules

Also the -r, --reverse flag is used for reversing the kernel module list.

kmon --reverse

Reversing the kernel modules

Customizing the colors

kmon uses the colors of the terminal as default but the highlighting color could be specified with -c, --color option. Alternatively, default text color can be set via -a, --accent-color option.

Supported colors

Supported terminal colors are black, red, green, yellow, blue, magenta, cyan, gray, darkgray, lightred, lightgreen, lightyellow, lightblue, lightmagenta, lightcyan, white.

kmon --color red

Supported Colors

Using a custom color

Provide a hexadecimal value for the color to use.

kmon --color 19683a

Using a custom color

Changing the accent color

Default text color might cause readability issues on some themes that have transparency. -a, --accent-color option can be used similarly to the -c, --color option for overcoming this issue.

kmon --color 6f849c --accent-color e35760

Changing the accent color

Unicode symbols

Use -u, --unicode flag for showing Unicode symbols for the block titles.

kmon --unicode

Unicode symbols

Setting the terminal tick rate

-t, --tickrate option can be used for setting the refresh interval of the terminal UI in milliseconds.

Setting the terminal tick rate

Roadmap

kmon aims to be a standard tool for Linux kernel management while supporting most of the Linux distributions.

Accessibility

For achieving this goal, kmon should be accessible from different package managers such as Snap* and RPM.

Dependencies

It is required to have the essential tools like dmesg and kmod on the system for kmon to work as expected. Thus the next step would be using just the system resources for these functions.

Features

Management actions about the Linux kernel should be applicable in kmon for minimizing the dependence on to command line and other tools.

Testing

kmon should be tested and reported on different architectures for further development and support.

Resources

About the project

Articles

Fedora 31 Debian 10 Manjaro 19
kmon on fedora kmon on debian kmon on manjaro
Ubuntu 18.04 openSUSE Void Linux
kmon on ubuntu kmon on opensuse kmon on voidlinux

Social Media

Funding

Patreon

Support the development of kmon and other projects by becoming a patron.

Patreon Button

Open Collective

Open Collective backers Open Collective sponsors

Support the open source development efforts by becoming a backer or sponsor.

Open Collective Button

License

GNU General Public License (3.0)

Copyright © 2020-2021, Orhun Parmaksız