Linux Survival Basics
Read-onlyShow Interface Addresses
You need interface state and assigned addresses.
Command
ip addrBefore you run this
System impact: Read-only. Low when scoped to the shown target.
When not to use it: Do not restart networking before recording current interface state.
Expected output
Interfaces with state, MAC, IPv4, and IPv6 addresses.
System impact
Read-only. Nothing changes. The command reads current state and prints diagnostic evidence.
Recovery / rollback: no state is changed.
When to use it
Use after route checks.
When not to use it
Do not restart networking before recording current interface state.
Example run
Commands shown
These are the commands shown for inspection. Treat them as an example, not proof that your system will behave identically.
ip addrip addr
next steps
Related commands
Show Linux Route Table
No default route means packets have nowhere to leave.
ip route
Show NetworkManager Device State
NetworkManager may know why the interface is disconnected.
nmcli device status
Show the Real User Cron Jobs
Cron problems often hide behind comments, blank lines, and copied folklore.
crontab -l | sed -n '/^[[:space:]]*#/d;/^[[:space:]]*$/d;p'
Show HTTPS Certificate with curl
curl can show the certificate path a client actually sees.
curl -Iv https://example.com/ 2>&1 | sed -n "/SSL connection/,/expire date/p"
Check Domain A Records
A renewal can fail because DNS points elsewhere.
dig +short example.com A
next diagnostic step
Where to go from this command
- Default route missing hub Use to confirm interface addressing.
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.