Archives and discs

An archive is where files go to be kept, not used: last decade's photos, finished projects, scanned papers. The danger is quiet: nothing fails until the day you need the file and the disc, the drive or the program to open it is gone. This lesson is about making that day go well.

An archive is not a backup

Lesson 2 separated backups from archives. The difference matters here:

A backup is a copy of files you still have. If it fails, you make a new one.
An archive is often the only place a file still exists, because you cleared it off your computer.

So an archive needs the 3-2-1 thinking too: at least two copies, on different media, one of them somewhere else. An archive on a single disc or a single drive is one accident away from gone.

Choose media for the long term

No storage lasts forever. Each kind fails in its own way.

Medium	Strengths	Weaknesses for archiving
External hard disk	Cheap per terabyte, holds everything	Mechanical; dislikes knocks; needs a working USB port and computer
SSD, USB stick, SD card	Small, fast, no moving parts	Flash memory is not meant to sit unpowered for many years. Do not make it the only long-term copy
Optical disc (CD, DVD, Blu-ray)	Write-once discs cannot be changed by ransomware or a wrong command; cheap; a shelf copy	Small capacity; quality varies widely; you need a drive to read them
Cloud storage	Somewhere else by design; no hardware to look after	Depends on the account, the payment and the company; access needs the password

The habit that matters more than any medium: copy forward. Every few years, check that your archive still reads, and copy it to newer media while the old one still works.

Optical discs

A burned disc is a good "somewhere else" copy: it sits on a shelf, needs no power, and a write-once disc cannot be altered after it is finished.

Disc	Capacity	Write
CD-R / CD-RW	700 MB	R: once. RW: rewritable
DVD±R / DVD±RW	4.7 GB (8.5 GB dual layer)	R: once. RW: rewritable
BD-R / BD-RE	25 GB (50 GB dual layer)	R: once. RE: rewritable

How long a burned disc lasts is hard to predict. It depends on the disc's make and materials, how well it was burned, and how it is stored; cheap discs have been known to become unreadable within a few years, while good discs kept well can last far longer. Treat any claimed lifespan with caution, and plan as if your discs could fail:

Use write-once discs (-R) for archives. Rewritable discs are made for reuse.
Verify every burn (see below), and keep two copies in different places.
Store discs in cases, upright, somewhere cool, dark and dry. Do not stick labels on them; write only with a soft disc marker.
Read your discs every year or two. When one gives errors, copy everything to new media from the good copy.

Disc images and ISO files

A disc image is one file that holds the complete contents of a disc, including its filesystem. The usual format is ISO (.iso), named after the ISO 9660 standard for disc filesystems.

You meet ISO files in two ways:

Installers. Linux distributions and many tools are published as bootable ISO files. To make a bootable disc, the image must be written to the disc as it is, not copied onto it as a file.
Archives. You can save a folder as an ISO file, keep it on a disk or in the cloud, and burn it later, on any computer.

text

  "Copy the .iso onto a data disc"       "Burn the image"
  ┌─────────────────────────┐            ┌─────────────────────────┐
  │ Disc                    │            │ Disc                    │
  │  └─ ubuntu.iso (a file) │            │  boot/  casper/  ...    │
  └─────────────────────────┘            └─────────────────────────┘
   does not boot                          boots: the disc IS the image

Before you burn a downloaded installer, check its SHA-256 checksum against the one the project publishes, as in lesson 4.

Burn and verify with Disc Writer

Disc Writer burns data discs and disc images on Linux. The parts that matter for archiving:

Task	In Disc Writer
Burn files and folders	Data disc: add items, enter a Disc label, select Burn
Write an ISO to disc	Burn image: writes `.iso` and `.img` files exactly as they are, so bootable installers stay bootable
Save a project as an ISO file	Save as ISO image… on Data disc. No disc or drive needed
Check a burn	Verify after writing, on by default in the options
Rehearse without using a disc	Simulate only: the laser stays off and nothing is written

Verify after writing reads the disc back after the burn:

You burned	How it is checked	A good result
A data disc	Checksums recorded during the burn are compared with the disc	Verified: disc contents match the recorded checksums
A disc image	The disc is compared with the image file byte for byte	Verified: disc matches the image byte for byte

If verification fails, the progress window shows Failed. Do not rely on that disc: burn again on a new disc, at a lower Write speed if the problem repeats. See Verify, simulate and inspect.

Two more options to understand:

Close the disc stops more sessions being added, and the disc then reads in more, and older, drives. Closing is permanent. For an archive disc that you will not add to, close it.
An ISO saved with Save as ISO image… includes Joliet (long names on Windows), Rock Ridge (long names and permissions on Linux) and ISO level 3, which allows single files larger than 4 GiB. See Save a project as an ISO file.

Formats that stay readable

A perfect disc is no use if no program can open what is on it. Prefer formats that are open, widely used and documented, because many programs can read them and will keep doing so.

Kind	Good choices for keeping	Be careful with
Documents	PDF (PDF/A is the archiving variant), plain text, OpenDocument	Formats only one app or subscription can open
Photos	JPEG, PNG, TIFF	Camera RAW files: each maker has its own. Keep a JPEG of the ones that matter too
Video and audio	MP4 (H.264), FLAC, MP3	Files with copy protection (DRM) tied to an account
Data	CSV, JSON, SQLite	Export files from a program you may not have in ten years
Bundles	A plain folder, ZIP or tar	Encrypted or password-protected archives without the password stored safely

A worked example: archiving a year of photos

Here is an archive of the 2025 photos, step by step:

Collect and check. Gather the photos in one folder, Photos-2025. Delete the blurry duplicates now, not later.
Fingerprint. Inside the folder, make a checksum list, so any future copy can be checked:
bash
```
cd Photos-2025
sha256sum *.jpg > SHA256SUMS.txt
```
Explain. Add a short README.txt: what the folder holds, when it was made, and that sha256sum -c SHA256SUMS.txt checks it.
Burn two discs with Disc Writer, Verify after writing on, Close the disc on. Label the cases.
Store them apart. One at home, one with family or at work. Keep a third copy on an external disk or in the cloud.
Put a reminder in your calendar to read both discs, and run the checksum check, in a year or two.

Stay safe

Never keep only one copy of anything you have archived and deleted from your computer.
Check every burn. Leave Verify after writing on, and do not rely on a disc that failed.
Check the image before a write-once burn. A burn on a write-once disc cannot be undone; Simulate only checks the drive and disc without using one up.
Test what you keep. Read archives every year or two, and copy forward before the media dies.
Store passwords for encrypted archives where you will find them in ten years, separately from the archive.
Verify downloaded images against the published checksum before you burn or boot them.

Check yourself

QuizArchives and discs

Question 1 of 6

You burned your 2020 photos to one DVD and deleted them from your laptop. What is the problem?

Score: 0

What you learned

An archive is often the only copy, so it needs two or more copies in different places.
All media age; the real protection is checking regularly and copying forward.
Disc lifespans vary widely. Use write-once discs, verify every burn and store them well.
An ISO is a whole disc in one file. Bootable images must be burned as images, not copied as files.
Disc Writer verifies data discs against recorded checksums and images byte for byte.
Open, widely used formats are the ones you will still be able to open.

Next steps

Practise a recovery and a restore: the hands-on lab for this track
Burn a data disc with Disc Writer
Burn a disc image

Archives and discs ​

An archive is not a backup ​

Choose media for the long term ​

Optical discs ​

Disc images and ISO files ​

Burn and verify with Disc Writer ​

Formats that stay readable ​

A worked example: archiving a year of photos ​

Stay safe ​

Check yourself ​

What you learned ​

Next steps ​