[MacOS] Check footprint and extract XZ compressed ISO file
18 May 2023
Table of Contents
Goal
You want to get an ISO file to ultimately install it. But as you want to ensure the version hasn’t been tampered, you can follow these checklist:
- download an ISO file,
- check its validity
- extract it (if compressed)
- burn it on a flash drive
For the example, let’s focus on a FreeBSD ISO file name FreeBSD-13.1-RELEASE-amd64-dvd1.iso.xz that you will get here:
NB: You may consider using the bootonly version as it is way smaller and however sufficient. The missing packages will be retrieved during the installation process.
Download
You may fetch a compressed version to get some time and bandwidth improvement. In the case where you take FreeBSD-13.1-RELEASE-amd64-dvd1.iso.xz instead of FreeBSD-13.1-RELEASE-amd64-dvd1.iso you will retrieve a file 26% smaller.
option 1
curl https://download.freebsd.org/releases/ISO-IMAGES/13.1/FreeBSD-13.1-RELEASE-amd64-dvd1.iso.xz --output FreeBSD-13.1-RELEASE-amd64-dvd1.iso.xz
option 2
wget https://download.freebsd.org/releases/ISO-IMAGES/13.1/FreeBSD-13.1-RELEASE-amd64-dvd1.iso.xz
Check file checksum
As you can see in the screenshot, there is two checksums file that you can get, depending on the SHA algorithm
- SHA265:
CHECKSUM.SHA256-FreeBSD-13.1-RELEASE-amd64 - SHA512:
CHECKSUM.SHA512-FreeBSD-13.1-RELEASE-amd64
Let’s use the SHA512 one:
wget https://download.freebsd.org/releases/ISO-IMAGES/13.1/CHECKSUM.SHA512-FreeBSD-13.1-RELEASE-amd64
Check the file hasn’t been tampered:
> shasum -a 512 FreeBSD-13.1-RELEASE-amd64-dvd1.iso.xz --check CHECKSUM.SHA512-FreeBSD-13.1-RELEASE-amd64 2>/dev/null | grep FreeBSD-13.1-RELEASE-amd64-dvd1.iso.xz
FreeBSD-13.1-RELEASE-amd64-dvd1.iso.xz: OK
Extract
xz -d FreeBSD-13.1-RELEASE-amd64-dvd1.iso.xz
You may use tar -xJvf FreeBSD-13.1-RELEASE-amd64-dvd1.iso.xz but it would extract the hierarchy contained into the ISO file.
Burn it
Follow these instructions: [MacOS] Burn ISO to flash drive or CD/DVD disk