knowledge/technology/applications/utilities/systeroid.md

obj	repo	rev
application	https://github.com/orhun/systeroid	2025-02-07

systeroid

sysctl 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.

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:

Section	Path	Description
abi	/proc/sys/abi/	execution domains & personalities
fs	/proc/sys/fs/	filesystem settings
kernel	/proc/sys/kernel/	global kernel information / miscellaneous settings
net	/proc/sys/net/	networking settings
sunrpc	/proc/sys/sunrpc/	SUN Remote Procedure Call settings
user	/proc/sys/user/	user namespace limits
vm	/proc/sys/vm/	memory management tuning buffer and cache management settings
dev	/proc/sys/dev/	device specific information
debug	/proc/sys/debug/	-

Usage

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

Options

Option	Description
-a, --all	display all variables
-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
-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

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

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]

Key Bindings

Key	Action
?, f1	show help
up/down, k/j, pgup/pgdown	scroll list
t/b	scroll to top/bottom
left/right, h/l	scroll documentation
tab, `	next/previous section
:	command
/	search
enter	select / set parameter value
s	save parameter value
c	copy to clipboard
ctrl-l, f2	show logs
r, f5	refresh
esc	cancel / exit
q, ctrl-c/ctrl-d	exit

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:

; systeroid ~ configuration file
; https://github.com/orhun/systeroid
;
; Each line either contains a comment or a command line argument grouped under a section.
; Run "systeroid --help" or "systeroid-tui --help" to get a list of all possible configuration options.

[general]
; display the deprecated parameters such as base_reachable_time and retrans_time while listing
; See https://bugzilla.redhat.com/show_bug.cgi?id=152435
display_deprecated = false
; path of the Linux kernel documentation
; this is distro dependent, systeroid checks the following locations as default:
; - /usr/share/doc/linux/
; - /usr/share/doc/linux-doc/
; - /usr/share/doc/linux-docs/
; - /usr/share/doc/kernel-doc-*/Documentation/
kernel_docs = "/usr/share/doc/linux"

[cli]
; ignore unknown variable errors
ignore_errors = true
; do not print variable after the value is set
quiet = false
; do not pipe output into a pager
; note that the default pager is less(1) and you can change it by using `PAGER` environment variable
no_pager = false
; display type for the parameter, available options are:
; - default: print the parameter name along with its value
; - name: print only the name of the parameter
; - value: print only the value of the parameter
; - binary: print only the value of the parameter without new line
display_type = "default"
; output type for the list, available options are:
; - default: print the output as is
; - tree: print the output in a tree-like format
; - json: print the output in JSON format
output_type = "default"

[cli.colors]
; available colors are defined in https://docs.rs/owo-colors/latest/owo_colors/colored/enum.Color.html
; default color for the symbols
default_color = "bright black"
; section colors
section_abi = "red"
section_fs = "green"
section_kernel = "magenta"
section_net = "blue"
section_sunrpc = "yellow"
section_user = "cyan"
section_vm = "bright red"
section_unknown = "white"

[tui]
; tick rate of the terminal
tick_rate = 250
; disable showing the parameter documentation
no_docs = true
; path for saving the changed kernel parameters
save_path = "/etc/sysctl.conf"
; file to save the logs
;log_file = "systeroid.log"

[tui.colors]
; available colors are defined in https://docs.rs/tui/latest/tui/style/enum.Color.html
; terminal foreground color
fg_color = "white"
; terminal background color
bg_color = "black"