Clarus Linux Reference Library

Package / system management

ldconfig configure dynamic linker run-time bindings/cache

update-alternatives manage symlinks for default commands

System Level ?

chkconfig SysV init service enable/disable (legacy)

systemctl control systemd services/units

systemd-analyze analyze system boot performance

loginctl control systemd logind sessions/users

timedatectl view/set system time and NTP settings

localectl view/set system locale and keyboard

hwinfo hardware detection and reporting

inxi system information summary tool

journalctl query and display systemd journal logs

Hardware / low-level

setpci query/modify PCI device configuration

setcap set Linux file capabilities

getcap display Linux file capabilities

freeipmi IPMI utilities (sensor/FRU, etc.)

ipmitool manage IPMI (BMC) for servers

numactl run a program with NUMA policy controls

numastat NUMA memory allocation statistics

tpm2-tools TPM 2.0 management/tool suite

cpupower CPU frequency and power management tool

lspci list PCI devices

lsusb list USB devices

dmidecode report system hardware information from BIOS

Weird but real

sl steam locomotive gag command (typo for ls)

yes output a string repeatedly

factor factor integers into primes

cal display a calendar

rev reverse characters in each line

fortune random quote/fortune cookie

cowsay print a talking cow with a message

toilet ASCII art text banners (figlet alternative)

figlet ASCII art text banners

Binary / forensics / reverse-engineering

objdump display object file information (disassembly)

objcopy copy/transform object files (strip, format)

readelf display ELF headers/sections

hexdump hex/ASCII dump of files

xxd hex dump and reverse (vim tool)

ldd print shared library dependencies for a binary

ltrace trace library calls made by a process

gdb GNU debugger

eu-readelf elfutils readelf (often richer output)

patchelf modify ELF binaries (rpath, interpreter)

Filesystem

debugfs ext2/3/4 filesystem debugger/inspector

tune2fs adjust ext2/3/4 filesystem parameters

e2fsck check and repair ext2/3/4 filesystems

resize2fs resize ext2/3/4 filesystem

dumpe2fs dump ext2/3/4 filesystem metadata

filefrag report file fragmentation on ext filesystems

quotacheck build/repair disk quota files

quota display user/group disk quota usage

repquota summarize disk quotas for a filesystem

debugreiserfs ReiserFS filesystem debugger/repair tools

find search for files in a directory hierarchy

tar archive files into a single file

rsync efficient file synchronization and transfer

Security / permissions / identity

semanage manage SELinux policy components

getenforce show current SELinux mode

setenforce set SELinux mode (enforcing/permissive)

ausearch search audit daemon logs

auditctl configure Linux audit subsystem rules

visudo safely edit sudoers file with validation

faillog show failed login attempts

lastlog show most recent login of all users

chcon change SELinux file security context

pam_tally2 PAM login failure counter (legacy; see faillock)

Terminal / shell power tools

script record a terminal session to a typescript file

scriptreplay replay a terminal session recorded by script

reset reset terminal to sane defaults

select-editor choose default editor (Debian/Ubuntu helper)

bind bash builtin: set/read readline key bindings

complete bash builtin: define tab-completion rules

compgen bash builtin: generate possible completions

disown bash builtin: detach a job from the shell

command command tells you about the CMDLN command you feed it!

coproc bash: start a coprocess with I/O pipes

watch run a command repeatedly and show output

cat concatenate and display files

less view file contents interactively

head output the first part of files

tail output the last part of files

tee read from stdin and write to stdout and files

printf format and print data

seq generate sequences of numbers

timeout run a command with a time limit

pv monitor progress of data through a pipeline

Process / system introspection (deep cuts)

atop advanced resource monitor (records history)

dstat multi-resource live stats

pidstat per-process CPU/IO stats

perf kernel performance profiler

watchdog watchdog daemon / keepalive for hung systems

tload graphical load average in terminal

powertop power usage and tuning for laptops/CPUs

uptimed track and report system uptime history

schedtool view/set process scheduler and priority

taskset set or view CPU affinity for a process

chrt set or view real-time scheduling attributes

turbostat Intel CPU frequency/idle/power reporting

freefall HP laptop accelerometer free-fall sensor tool

Storage & Block Devices

wipefs wipe filesystem/RAID signatures from a device

blkid identify block devices (UUID, type, label)

losetup configure loop devices for disk images

cryptsetup manage LUKS/dm-crypt encrypted volumes

mountpoint test whether a directory is a mount point

findmnt list mounted filesystems in a tree/table

statx extended file status (statx syscall helper)

badblocks scan a block device for bad sectors

btrfsctl legacy Btrfs control utility

btrfs-progs Btrfs userspace tools (mkfs, scrub, balance)

zpool manage ZFS storage pools

zfs manage ZFS datasets (filesystems, snapshots)

ntfs-3g NTFS driver/userspace mount helper

lsblk list block devices

Text / data processing (esoteric but handy)

column format text into aligned columns

nl number lines of a file

tac print file in reverse line order

rev reverse characters in each line

csplit split a file into sections by pattern/lines

fold wrap long lines to a given width

iconv convert text between character encodings

unix2dos convert Unix line endings to DOS/Windows

shuf shuffle lines / randomize input

comm compare two sorted files line-by-line

watchmedo watchdog CLI: run a command on file changes

datamash command-line statistics / grouping on text data

csvtool manipulate and query CSV files

grep search text for patterns

sed stream editor for filtering and transforming text

awk pattern scanning and processing language

cut extract sections from lines of text

sort sort lines of text files

wc count lines, words, and bytes

tr translate or delete characters

paste merge lines of files

xargs build and execute command lines from input

Networking (beyond ping & ssh)

tc traffic control

ethtool query/set Ethernet device settings

arp view/modify ARP table (legacy; see ip neigh)

arptables ARPTABLES firewall rules for ARP packets

bridge configure Linux Ethernet bridges (iproute2)

brctl legacy bridge configuration tool

iw configure wireless devices (nl80211)

iwconfig legacy wireless configuration tool

rfkill enable/disable wireless devices (rfkill switch)

tcpdump packet capture and analysis (CLI)

tshark Wireshark CLI packet analyzer

nethogs per-process network bandwidth monitor

iftop top-like bandwidth monitor by connection

ipcalc IP subnet calculator (CIDR/netmask)

socat bidirectional data relay (netcat on steroids)

fuser show which processes use a file/socket

lsof list open files and the processes using them

conntrack view/manage netfilter connection tracking

tracepath trace network path (like traceroute, no root)

mtr ping + traceroute combined live report