Build the disposable machine, snapshot it, and prove the revert works

short · 45 min

Task

Build the guest that the rest of this course runs on, take a named baseline snapshot, deliberately damage the guest, and revert. The exercise is not the installation -- it is proving that the revert actually returns the machine to the baseline, because an untested snapshot is the same kind of assumption as an untested backup.

Steps

  1. Create the guest, install the operating system, and apply updates. Record the hypervisor, guest operating system and version in lab/bench/guest.txt.
  2. Shut the guest down cleanly and take a snapshot named clean-baseline. Record the snapshot name and the date in lab/bench/snapshots.csv with header name,taken,powered_off,why.
  3. Start the guest and create a file at a path you will remember, containing today's date. Record the path in lab/bench/marker.txt.
  4. Revert to clean-baseline, start the guest, and confirm the file is gone. Record the result in lab/bench/revert.txt as one line reading marker present: yes or marker present: no.
  5. Write lab/bench/isolation.csv with header setting,value,what_it_blocks recording the network mode, shared folders, clipboard sharing and USB pass-through, and what each one would let cross the boundary if it were enabled.

Verify

grep -c . lab/bench/guest.txt
awk -F, 'NR>1 && NF>=4 {n++} END {print n" snapshot(s) recorded"}' lab/bench/snapshots.csv
grep -Ec 'marker present: no' lab/bench/revert.txt
awk -F, 'NR>1 && NF>=3 {n++} END {print n" isolation setting(s)"}' lab/bench/isolation.csv
grep -Eic 'host-only|internal|isolated' lab/bench/isolation.csv

The revert line must read no. If the marker survived the revert you did not revert -- you took a second snapshot, or you reverted to the wrong one, and every later lab in this course would have been running on a machine that accumulates its own damage.

Notes

Name snapshots for what they are. clean-baseline-after-updates is worth something in three weeks; snapshot1 is not. Two or three named points is plenty -- a chain of thirty performs badly and is easy to get lost in.

This is an independent study companion for CompTIA A+ Core 2 220-1202 and is not produced by or endorsed by CompTIA.