Ubuntu-L5-Field Marshal
A. File & Filesystem (Advanced)
basename – Extract filename from path
Extracts filename from a full path. Ignores directory components.
dirname – Extract directory from path
Extracts directory path from a full path.
Opposite of basename.
realpath – Resolve absolute path
Resolves absolute path with symlinks.
Eliminates .. and relative components.
readlink – Print symbolic link target
Displays symbolic link target. Used to inspect symlinks.
statfs – Filesystem statistics
Shows filesystem statistics. Reports block and inode usage.
rename – Batch rename files
Batch renames files using patterns. Efficient for mass file operations.
chattr – Change file attributes
Changes extended file attributes. Can make files immutable.
lsattr – List file attributes
Lists extended file attributes.
Used with chattr.
statx – Extended file stats
Displays extended file metadata. Provides low-level filesystem info.
syncfs – Sync filesystem
Flushes filesystem buffers. Ensures data is written to disk.
B. Disk, Storage & Hardware
blkid – Block device attributes
Shows block device UUIDs and types. Used in mounting and fstab.
findmnt – List mounted filesystems
Lists mounted filesystems.
More structured than mount.
mountctl – Control mounts
Controls mount points via systemd. Advanced mount management.
fsck – Filesystem check
Checks and repairs filesystems. Run on unmounted disks.
tune2fs – Tune ext filesystems
Adjusts ext filesystem parameters. Used for performance tuning.
resize2fs – Resize ext filesystem
Resizes ext filesystems. Works online or offline.
badblocks – Check disk for bad sectors
Scans disk for bad sectors. Used during disk diagnostics.
hwinfo – Hardware info
Displays detailed hardware information.
More verbose than lshw.
lsusb – USB devices
Lists USB devices. Used for peripheral debugging.
lspci – PCI devices
Lists PCI devices. Common for GPU and NIC checks.
C. Networking (Advanced)
ip route – Routing table
Displays routing table. Critical for network debugging.
ip neigh – ARP table
Shows neighbor (ARP) cache. Maps IPs to MAC addresses.
traceroute – Network path trace
Traces network hops. Identifies routing issues.
mtr – Traceroute + ping
Combines ping and traceroute. Live network diagnostics.
tcpdump – Packet capture
Captures network packets. Used for deep traffic analysis.
nmap – Network scanning
Scans networks and ports. Security and discovery tool.
ethtool – Network interface settings
Displays NIC settings. Used for link speed and offload tuning.
nmcli – NetworkManager CLI
Controls NetworkManager. CLI network configuration.
whois – Domain lookup
Queries domain ownership info. Used in DNS investigations.
arp – Address resolution table
Displays ARP table. Legacy but still useful.
D. Process, Performance & CPU
nice – Set process priority
Starts process with priority. Lower value = higher priority.
renice – Change priority
Changes running process priority. Requires privileges.
htop – Interactive process viewer
Interactive process monitor.
Improved top.
atop – Advanced system monitor
Advanced system resource monitor. Records historical data.
pidstat – Per-process stats
Reports per-process statistics. Useful for CPU and I/O analysis.
perf – Performance analysis
Linux performance profiler. Used for kernel and CPU analysis.
uptime – System load
Shows system load averages. Quick health check.
watchdog – Monitor system health
Monitors system health. Triggers recovery on hangs.
schedtool – Scheduler control
Controls process scheduling. Advanced scheduler tuning.
taskset – CPU affinity
Sets CPU affinity. Pins process to specific cores.
E. Logs, Debugging & Tracing
journalctl -u – Logs by service
Shows logs for a service. Primary systemd log tool.
coredumpctl – Core dump analysis
Manages core dumps. Used for crash analysis.
strace -p – Attach syscall tracer
Attaches syscall tracer. Debugs live processes.
ltrace – Library call tracing
Traces library calls.
Complements strace.
pmap – Process memory
Displays process memory map. Used in memory debugging.
procinfo – System info
Summarizes system info. Legacy but informative.
dstat – Resource statistics
Resource statistics tool. Combines vmstat, iostat, netstat.
vmstat -s – Memory summary
Memory summary statistics. Kernel-level insight.
free -w – Detailed memory
Detailed memory usage. Shows buffers accurately.
uptime -p – Pretty uptime
Human-readable uptime. Simplified format.
F. Text Processing (Expert)
paste – Merge file columns
Merges lines from files. Column-wise merge.
join – Join files
Joins files on a key. Similar to SQL join.
nl – Number lines
Numbers file lines. Useful for reference.
fmt – Text formatter
Formats text paragraphs. Adjusts line width.
fold – Line wrapping
Wraps long lines. Controls column width.
expand – Tabs to spaces
Converts tabs to spaces. Text normalization.
unexpand – Spaces to tabs
Converts spaces to tabs.
Inverse of expand.
iconv – Encoding conversion
Converts text encodings. Used for UTF fixes.
dos2unix – Line ending fix
Fixes Windows line endings. Removes CRLF.
unix2dos – Windows line endings
Adds Windows line endings. For Windows compatibility.
G. Shell & Environment Mastery
bind – Readline bindings
Configures readline keys. Customizes shell input.
complete – Bash autocompletion
Defines command autocompletion. Used in advanced bash setups.
compgen – Generate completions
Generates completion matches. Backend for autocomplete.
shopt – Shell options
Toggles bash behavior. Shell feature control.
exec – Replace shell
Replaces current shell. No new process spawned.
disown – Detach jobs
Detaches job from shell. Survives logout.
jobs – Background jobs
Lists background jobs. Shell job control.
fg – Foreground job
Brings job to foreground. Resumes execution.
bg – Resume background job
Resumes job in background. Keeps terminal free.
wait – Wait for process
Waits for process completion. Used in scripts.
H. Users, Groups & Security
useradd – Create user
Creates new user. Low-level user creation.
usermod – Modify user
Modifies user properties. Groups, shell, UID.
userdel – Delete user
Deletes user account. Optionally removes home.
groupadd – Create group
Creates a group. Used in access control.
groups – Show group memberships
Shows user groups. Permission debugging.
passwd – Change password
Changes user password. Also locks accounts.
faillog – Login failure logs
Shows login failures. Security auditing.
lastlog – Last login info
Shows last login per user. Account usage tracking.
newgrp – Switch group
Switches primary group. Without logout.
su – Switch user
Switches user identity. Requires password.
I. Scheduling, Boot & Power
crontab -l – List cron jobs
Lists cron jobs. User-specific schedules.
atq – List at jobs
Lists scheduled at jobs. One-time tasks.
atrm – Remove at job
Removes at jobs. Cancels execution.
shutdown -r – Reboot schedule
Schedules reboot. Graceful system restart.
wall – Broadcast message
Broadcasts message. All logged-in users.
write – Message user
Sends message to user. Terminal-to-terminal.
login – Login prompt
Starts login session. Used by getty.
logout – End session
Ends user session. Shell termination.
halt – Stop CPU
Stops CPU execution. Immediate shutdown.
reboot -f – Force reboot
Forces reboot. Bypasses safety checks.
J. Packaging, Builds & System
dpkg -l – List packages
Lists installed packages. Low-level package manager.
dpkg -i – Install .deb
Installs .deb files.
No dependency resolution.
apt-cache policy – Package versions
Shows package versions. Repository diagnostics.
apt-key – Repository keys
Manages repository keys. Deprecated but still seen.
add-apt-repository – Add repo
Adds new repositories. Simplifies repo management.
ldd – Shared libraries
Lists shared libraries. Binary dependency check.
ldconfig – Linker cache
Updates linker cache. System library management.
uname -r – Kernel version
Shows kernel version. Critical for compatibility.
lsmod – Loaded kernel modules
Lists loaded kernel modules. Driver inspection.
modprobe – Load kernel module
Loads kernel modules. Handles dependencies.
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