systeroid — A more powerful alternative to sysctl(8).

sysctl(8) is a utility on Unix-like operating systems that is used to read and modify the attributes of the kernel such as its version number, maximum limits, and security settings*. systeroid is "sysctl on steroids". It can do everything that sysctl does and even more. It provides a safer, more performant, and user-friendly CLI/TUI for managing the kernel parameters at runtime.

systeroid is implemented using procfs which is the virtual file system that is typically mapped to a mount point named /proc at boot time. This means checking the value of some kernel parameter requires opening a file in this virtual filesystem, reading its contents, parsing them, and closing the file. In Linux, these dynamically configurable kernel options are available under /proc/sys which contains directories representing the sections of the kernel and readable/writable virtual files. For example, to enable/disable IP forwarding, 1 or 0 could be written in /proc/sys/net/ipv4/ip_forward or systeroid ip_forward=1 command can be used to change the value of the parameter.

Although systeroid does not need the parameter section to be specified explicitly, it is important to know the sections and their areas of impact. Here are the available kernel sections according to the Linux kernel documentation:

• Requirements
• Installation
  • Cargo
  • Arch Linux
  • Alpine Linux
  • Binary releases
  • Building from source
  • Docker
  • Images
  • Usage
  • Building
• Usage
  • Options
  • Examples
  • Listing parameters
  • Filtering by section
  • Displaying values
  • Setting values
  • Loading values from a file
  • Loading values from the system directories
  • Searching parameters
  • Showing information about parameters
  • Verbose logging
• TUI
  • Usage
  • Key Bindings
  • Examples
  • Launching
  • Showing help
  • Scrolling
  • Toggling the kernel section
  • Searching
  • Setting values
  • Saving values
  • Running commands
  • Copying to clipboard
  • Changing the colors
  • Viewing the parameter documentation
  • Setting the refresh rate
  • Logging
• Configuration
• Resources
  • References
  • Logo
  • Social Links
  • In The Media
  • Funding
• Contributing
• License
• Copyright

Requirements

• Rust (>=1.64.0) (see building from source)
• libxcb (for clipboard support)
• linux-documentation (for viewing the documentation)

To install the runtime dependencies:

• on Arch Linux: pacman -S libxcb libxkbcommon linux-docs
• on Debian/Ubuntu: apt-get install libx11-dev libxcb-shape0-dev libxcb-xfixes0-dev libxkbcommon-dev linux-doc
• on Fedora: dnf install libX11-devel kernel-doc

Installation

Cargo

systeroid is available on crates.io:

cargo install systeroid
cargo install systeroid-tui

Arch Linux

systeroid can be installed from the community repository using pacman:

pacman -S systeroid

Alpine Linux

systeroid is available for Alpine Edge. It can be installed via apk after enabling the community repository.

apk add systeroid

Binary releases

See available releases that are automated by Continuous Deployment workflow.

Building from source

# clone the repository
git clone https://github.com/orhun/systeroid && cd systeroid/

# binaries will be located at:
# - target/release/systeroid
# - target/release/systeroid-tui
CARGO_TARGET_DIR=target cargo build --release

Also see requirements.

Docker

Images

Docker builds are automated and images are available in the following registries:

• Docker Hub
• GitHub Container Registry

Usage

The following command can be used to interactively view the documentation of selected parameters:

docker run --rm -it "orhunp/systeroid:${TAG:-latest}" --tui

Docker containers share the host system's kernel and its settings thus access to /proc and /sys are restricted for security. That is why it is not possible (and not recommended) to tweak the kernel parameters within a container. *

Building

Custom Docker images can be built from the Dockerfile:

docker build -t systeroid .

Usage

systeroid [options] [variable[=value] ...] --load[=<file>]

Options

-a, --all           display all variables (-A,-X)
-T, --tree          display the variables in a tree-like format
-J, --json          display the variables in JSON format
    --deprecated    include deprecated variables while listing
-e, --ignore        ignore unknown variable errors
-N, --names         print only variable names
-n, --values        print only variable values
-b, --binary        print only variable values without new line
-p, --load          read values from file (-f)
-S, --system        read values from all system directories
-r, --pattern <expr>
                    use a regex for matching variable names
-q, --quiet         do not print variable after the value is set
-w, --write         only enable writing a value to variable
-E, --explain       provide a detailed explanation for variable
-D, --docs <path>   set the path of the kernel documentation
-P, --no-pager      do not pipe output into a pager
-v, --verbose       enable verbose logging
    --tui           show terminal user interface
-c, --config <path> set the path of the configuration file
-h, --help          display this help and exit (-d)
-V, --version       output version information and exit

Most of the arguments/flags are inherited from sysctl so they have the same functionality.

Examples

Listing parameters

# list all parameters
systeroid -A

# list parameters in a tree-like format
systeroid -T

# list parameters in JSON format
systeroid -J

To disable colors, set the NO_COLOR environment variable.

Filtering by section

# only list parameters in the "kernel" section
systeroid kernel

# only list parameters in the "vm" and "user" sections
systeroid vm user

Displaying values

# print the name and value of a parameter (in "name=value" format)
systeroid kernel.hostname

# print only the value of a parameter
systeroid -n kernel.hostname

# print the name and values of the multiple parameters
systeroid kernel.hostname user.max_user_namespaces

Setting values

# set the value of a parameter
systeroid kernel.domainname="example.com"

# set the values of multiple parameters and ignore errors
systeroid -e kernel.dmesg_restrict=0 vm.panic_on_oom=1 unknown_param="test"

# set the values of multiple parameters and enforce the "name=value" format
systeroid -w fs.dir-notify-enable=1 net.mptcp.enabled=1 vm.oom_kill_allocating_task

Loading values from a file

Parameter values can be set from an INI file.

sysctl.conf:

# Use kernel.sysrq = 1 to allow all keys.
# See https://www.kernel.org/doc/html/latest/admin-guide/sysrq.html for a list
# of values and keys.
kernel.sysrq = 16

# Append the PID to the core filename
kernel.core_uses_pid = 1

; Enable hard and soft link protection
; (If a line begins with a single '-', any attempts to set the value that fail will be ignored.)
-fs.protected_hardlinks = 1
fs.protected_symlinks = 1

To load it:

systeroid --load sysctl.conf

If no file is given, values are loaded from /etc/sysctl.conf as default:

systeroid --load

Specifying "-" as file name means reading data from standard input:

systeroid --load -

Loading values from the system directories

The list of default system directories are the following:

• /etc/sysctl.d
• /run/sysctl.d
• /usr/local/lib/sysctl.d
• /usr/lib/sysctl.d
• /lib/sysctl.d
• /etc/sysctl.conf

Use --system flag to load the files with ".conf" extension in these directories:

systeroid --system

Searching parameters

# search parameters using regex patterns
systeroid -r 'net.ipv4.conf.(eth|wlan)0.arp'
systeroid -r '^net.ipv6'

Example output of combining search with listing:

$ systeroid --names --pattern 'kernel.*_max$' --tree

kernel
├── ngroups_max
├── pid_max
└── sched_util_clamp_max

Showing information about parameters

systeroid can dump the parameter information from the kernel documentation. This is useful if you don't know what a parameter is used for.

# show information about a parameter
systeroid --explain oom_dump_tasks

Kernel documentation should be present in one of the following paths for parsing upon first launch:

• /usr/share/doc/linux
• /usr/share/doc/linux-doc
• /usr/share/doc/linux-docs
• /usr/share/doc/kernel-doc-*/Documentation

Then the parsed data is cached in $HOME/.cache/systeroid-core and used from there as long as the documentation is not updated. The caching mechanism can be disabled via setting the NO_CACHE environment variable.

This is a design choice due to the fact that different versions of kernels might be installed on different systems so the documentation might be too new or old if systeroid was to be shipped with a fixed set of parameter descriptions bundled in. With the parsing approach, documentation is always kept up-to-date.

However, this means you need to:

• either install the kernel documentation package (based on your distribution)
  • on Arch Linux: pacman -S linux-docs
  • on Debian/Ubuntu: apt-get install linux-doc
  • on Fedora: dnf install kernel-doc
• or explicitly specify the path of the kernel documentation.

# specify the kernel documentation path explicitly
# (not needed if you have the kernel documentation installed as a package)
systeroid -E user.max_user_namespaces --docs /usr/share/doc/linux

To change the default pager (less(1)), you can use the PAGER environment variable. Also, you can simply use --no-pager flag to disable it.

systeroid -E kernel.ctrl-alt-del --no-pager

It is also possible to retrieve information about multiple parameters:

systeroid -E --pattern '.*ipv4.*' --no-pager

Verbose logging

--verbose flag can be used to enable verbose logging:

systeroid --verbose

Also, RUST_LOG environment variable can be set accordingly to filter based on different log levels.

RUST_LOG=trace systeroid

TUI

Usage

systeroid-tui [options]

-t, --tick-rate <ms>
                    set the tick rate of the terminal [default: 250]
-D, --docs <path>   set the path of the kernel documentation
    --save-path <path>
                    set the path for saving the changed parameters
-s, --section <section>
                    set the section to filter
-q, --query <query> set the query to search
    --bg-color <color>
                    set the background color [default: black]
    --fg-color <color>
                    set the foreground color [default: white]
-n, --no-docs       do not show the kernel documentation
    --deprecated    include deprecated variables while listing
-c, --config <path> set the path of the configuration file
-h, --help          display this help and exit
-V, --version       output version information and exit

Key Bindings

Examples

Launching

Simply run systeroid-tui to launch the terminal user interface. Alternatively, you can use systeroid --tui command (which runs systeroid-tui under the hood if it is found in PATH).

Showing help

Help menu and key bindings can be shown via pressing ?:

Scrolling

Use up/down keys to scroll the parameter list. Alternatively, use t/b to scroll to the top/bottom.

Use left/right to scroll the parameter documentation.

Toggling the kernel section

Press tab or ` to toggle the kernel section for filtering entries in the parameter list.

Order of the sections is all-abi-fs-kernel-net-sunrpc-user-vm.

--section argument can be used to start systeroid-tui with the specified section for filtering.

systeroid-tui --section kernel

Searching

Press / and type in your query to search for parameters.

Alternatively, you can start systeroid-tui with a pre-defined search query by using --query argument.

systeroid-tui --query "fs.quota"

Setting values

Press enter to select a parameter and set its value via command prompt.

You can press r to refresh the values in the parameter list.

Saving values

Press s to set a parameter value via command prompt and save its value to a file specified via --save-path.

Default save path is /etc/sysctl.conf and the values can be loaded via systeroid --load.

$ systeroid-tui --save-path /etc/sysctl.d/custom.conf

$ systeroid --system

Running commands

Press : to open the command prompt for running a command. Available commands are:

Copying to clipboard

Press c to show the options menu for copying the name, value, or documentation of the selected parameter.

* systeroid-tui should be built with clipboard feature for enabling the clipboard support.

Changing the colors

Use --bg-color and --fg-color arguments to customize the colors of the terminal user interface.

# use a color name for setting the foreground color
systeroid-tui --fg-color blue

# use hexadecimal values for setting foreground/background colors
systeroid-tui --bg-color ffff99 --fg-color 003366

# use transparent background
systeroid-tui --bg-color reset

Viewing the parameter documentation

To view the documentation as parameters are being selected on the list, kernel documentation should be parsed as explained in the "Showing information about parameters" section. A specific path for kernel documentation can be given via --docs argument or KERNEL_DOCS environment variable if it is not found in one of the locations that are checked as default.

To disable this feature altogether, use --no-docs flag.

Setting the refresh rate

It is possible to specify a value in milliseconds via --tick-rate argument for tweaking the refresh rate of the terminal which might be necessary in some cases where better performance is desired.

systeroid-tui --tick-rate 500

Logging

To view the log messages, press ctrl-l. It will bring up a pane in the TUI for analyzing the logs:

This pane consists of two parts. Left is the target selector and on the right side the logging messages view scrolling up.

The target selector controls:

• Capturing of log messages by the logger.
• Selection of levels for display in the logging message view.

The two columns have the following meaning:

• Code EWIDT: E stands for Error, W for Warn, and similarly Info, Debug and Trace.
  • Inverted characters (EWIDT) are enabled log levels in the view.
  • Normal characters show enabled capturing of a log level per target.
  • If any of EWIDT are not shown, then the respective log level is not captured.

This logger pane has the following key bindings and they are only activated while the logs are being shown:

For saving the logs to a file, you can use the --log-file argument:

systeroid-tui --log-file systeroid.log

RUST_LOG environment variable can be used to set the log level accordingly.

RUST_LOG=debug systeroid-tui

Configuration

systeroid can be configured with a configuration file that uses the INI format. It can be specified via --config or SYSTEROID_CONFIG environment variable. It can also be placed in one of the following global locations:

• $HOME/.config/systeroid/systeroid.conf
• $HOME/.systeroid/systeroid.conf

# set the config path via argument
systeroid --config config/systeroid.conf

# set the config path via env
SYSTEROID_CONFIG=config/systeroid.conf systeroid

# use a global path
mkdir -p "$HOME/.config/systeroid"
cp config/systeroid.conf "$HOME/.config/systeroid"
systeroid

See the example systeroid.conf for the configuration options.

Resources

References

• sysctl - source code
• sysctl - Wikipedia
• sysctl - ArchWiki

Logo

systeroid logo was originally painted by Ryan Tippery as a part of the Compositions art collection and it is put together by me using the Filled Spots font. Shout out to Ryan for letting me use his painting for the logo! <3 Kudos!

Social Links

In The Media

• Systeroid: Best Way To Set Linux Kernel Parameters (YouTube / Brodie Robertson)

Funding

If you find systeroid and/or other projects on my GitHub profile useful, consider supporting me on GitHub Sponsors or becoming a patron!

Contributing

See our Contribution Guide and please follow the Code of Conduct in all your interactions with the project.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache 2.0 License, shall be dual licensed as above, without any additional terms or conditions.

License

Licensed under either of Apache License Version 2.0 or The MIT License at your option.

Copyright

Copyright © 2022-2024, Orhun Parmaksız