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Hosting Operations

Read-only

Check a Domain A Record

You need to see the IPv4 address a domain currently resolves to.

Command

dig +short example.com A

Before you run this

System impact: Read-only. Low when scoped to the shown target.

When not to use it: Do not assume one resolver represents every user during DNS propagation.

Expected output

One or more IPv4 addresses.

System impact

Read-only. Nothing changes. The command queries DNS.

Recovery / rollback: no state is changed.

When to use it

Use this during DNS cutovers, migrations, and stale resolver debugging.

When not to use it

Do not assume one resolver represents every user during DNS propagation.

Watch this command run

Command transcript

This sanitized transcript shows the commands and output shape without exposing host details.

demo@lab:~$

$ dig +short example.com A

203.0.113.10

$ dig +short example.com CNAME

example.com.

$ curl -I http://example.com

HTTP/1.1 301 Moved Permanently
Location: https://example.com/
View commands shown

These are the commands shown in the sanitized transcript.

Commands shown

  1. dig +short example.com A
  2. dig +short www.example.com CNAME
  3. curl -I http://example.com

next steps

Related commands

Hosting Operations Read-only

Check the Current Release Symlink

The deploy finished. The symlink told me what was actually live.

readlink -f /srv/www/example.com/current
Hosting Operations Read-only

Check HTTP to HTTPS Redirect

HTTPS worked. The plain HTTP redirect still mattered.

curl -I http://example.com
Hosting Operations Can be slow

Find Feed Links Missing from the Sitemap

Your feed can advertise URLs that the sitemap never lists.

grep -o '<link>https://example.com/[^<]*</link>' public/feed.xml | sed 's#<link>##;s#</link>##' | while read -r url; do grep -q "$url" public/sitemap.xml || echo "$url"; done
Hosting Operations Can be slow

Find HTML Pages Missing from the Sitemap

A page can exist in the build but never make it into the sitemap.

find public -name '*.html' -print | sed 's#^public#https://example.com#' | while read -r url; do grep -q "$url" public/sitemap.xml || echo "$url"; done
Hosting Operations Read-only

Snapshot Git Status Before Recovery

Before rollback commands, capture the branch and dirty files.

cd /lab/git-recovery-rollback && git status --short --branch
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.

  • lpic1:109-networking
  • lfcs:networking
  • lfcs:operations-deployment
  • lfcs:services-logs
  • linuxplus:provisional
  • linuxplus:troubleshooting
  • risk:read-only

Useful for

  • LPIC-1 style command-line practice
  • LFCS style performance tasks
  • Linux+ style troubleshooting review

Independent study support only. No affiliation, endorsement, exam dumps, or real exam questions.