Linux Survival Basics
Read-onlyRead Load Average Before You React
You need a fast snapshot of system load and how long the machine has been running.
Command
uptimeBefore you run this
System impact: Read-only. Low when scoped to the shown target.
When not to use it: Do not assume high load always means CPU saturation; blocked I/O can raise load too.
Expected output
A single line showing current time, uptime, user count, and 1, 5, and 15 minute load averages.
System impact
Read-only. Nothing changes. The command prints uptime, users, and load averages.
Recovery / rollback: no state is changed.
When to use it
Use at the start of performance triage to see whether pressure is rising or falling.
When not to use it
Do not assume high load always means CPU saturation; blocked I/O can raise load too.
next steps
Related commands
Find the Files Eating Your Disk
The disk was full, but guessing at folders was the slow part.
find /var -type f -printf '%s %p\n' | sort -nr | head -20
Compare Kernel and Distro Versions
The distro version and kernel version answer different questions.
printf 'kernel=%s arch=%s distro=%s\n' "$(uname -r)" "$(uname -m)" "$(lsb_release -ds)"
Show Recent Server Reboots
Confirm whether the server actually rebooted and when.
last -x reboot | head -5
Scan a Host SSH Key
Keyscan collects a presented key; it does not verify trust.
ssh-keyscan -t ed25519 hostname
Test Apache Config Without Reloading
Apache can check syntax before you reload a live site.
sudo apachectl configtest
Study mapping
Use this as independent command practice: read the notes, predict the output, then compare it with the example before using a real shell.
Independent study support only. No affiliation, endorsement, exam dumps, or real exam questions.