Your First Linux Backup: 7 Steps to Create and Check It

Start with a separate workspace

Use Bash on a Linux machine with GNU tar, gzip, GNU Coreutils and find. Ubuntu and Debian commonly provide these tools. This lab needs no sudo and uses only files you create. Run the steps in the same terminal; if any command reports an error, stop and resolve it before continuing.

command -v tar gzip sha256sum mktemp find
tar --version

Confirm that the version output identifies GNU tar and that every requested tool has a path. Then create a unique lab directory under your home folder:

backup_lab=$(mktemp -d "$HOME/sa-backup-lab.XXXXXX")
printf 'Lab directory: %s\n' "$backup_lab"

Add a few files worth checking

Make two ordinary text files and one hidden file. The hidden file is deliberate: it gives you something easy to miss if you later replace a directory argument with a shell wildcard.

mkdir "$backup_lab/source" "$backup_lab/archives"
mkdir "$backup_lab/source/notes"
printf 'A small backup practice folder.\n' > "$backup_lab/source/readme.txt"
printf 'Remember to test recovery.\n' > "$backup_lab/source/notes/todo.txt"
printf 'DEMO_MODE=yes\n' > "$backup_lab/source/.demo-settings"

These are disposable examples, not real application data or credentials. Leave them unchanged until the comparison in Step 06.

Know what should go into the archive

find "$backup_lab/source" -type f -print

You should see paths ending in readme.txt, notes/todo.txt and .demo-settings. Their order may differ. This small inventory is your reference when you inspect the archive.

Keep the archive outside the source

The source and archive directories are siblings. This keeps the output file out of the directory tar is reading.

tar --create --gzip \
  --file="$backup_lab/archives/files.tar.gz" \
  --directory="$backup_lab/source" . \
  && printf 'Archive created.\n'

--create builds the archive, --gzip compresses it, and --file names the output. GNU tar often prints nothing on success here; the final message appears only if tar exits successfully.

Check the names before trusting the file

tar --list --gzip --file="$backup_lab/archives/files.tar.gz"

The listing should include these entries, although the order can vary:

./
./readme.txt
./notes/
./notes/todo.txt
./.demo-settings

A plausible file size would not tell you that the hidden file is missing. A listing can. It still does not prove that the saved contents match the source.

Check the copy against the quiet source

GNU tar can compare archive members with their matching files on disk. Use the same source directory as before:

tar --compare --gzip \
  --file="$backup_lab/archives/files.tar.gz" \
  --directory="$backup_lab/source" \
  && printf 'Archived members match the source.\n'

With the unchanged lab files, expect the final message and no difference reports. GNU tar checks member contents and metadata such as size, mode, ownership and modification time. Reported differences or errors need attention.

Save a checksum before moving the archive

Record a SHA-256 checksum of the archive, then check it immediately. The parentheses run this block in a subshell, so your terminal keeps its original working directory.

(
  cd "$backup_lab/archives" &&
  sha256sum files.tar.gz > files.tar.gz.sha256 &&
  sha256sum --check files.tar.gz.sha256
)

files.tar.gz: OK

That result means the archive matches the checksum just recorded. After copying the archive and checksum file elsewhere, run the check from their destination directory. Keep the original checksum: regenerating it from a damaged copy would simply record that damaged copy.

What you have checked so far

Keep the lab directory, its source files, the archive and the checksum for Lesson 03. Nothing needs to be scheduled yet. First, make sure you can get the files back.