Check a Downloaded ISO Image For Errors/es

Introducción

Antes de grabar su imagen ISO descargada (o utilizarla como disco virtual en Virtualbox), es "muy" recomendable que primero revise si el archivo no ha sido corrompido. Las consecuencias de no hacerlo, principalmente si pretende instalar Manjaro como su sistema operativo principal, debería ser obvio, que una imagen corrupta podría resultar en una instalación corrupta.

Para realizar la revisión, primero debe descargar el archivo checksum del mismo sitio web fuente de su imagen ISO escogida. Un archivo checksum tendrá el mismo nombre que la imagen ISO que se usará; con la unica diferencia que al final terminará en -sha1.sum o -sha256.sum. Por ejemplo, el checksum apropiado para el archivo manjaro-xfce-0.8.1-x86_64.iso (lanzamiento 0.8.1 de Manjaro 64 bits con el escritorio XFCE) seria:

• manjaro-xfce-0.8.1-x86_64-sha1.sum, y/o
• manjaro-xfce-0.8.1-x86_64-sha256.sum

SHA1 y SHA256

The 'sha' part of the checksum file name stands for Secure Hash Algorithm. This algorithm is used to generate a particular code unique to the downloaded ISO image. sha1 and sha256 are different versions of the algorithm that you can use to do this. Whilst sha1 is the most commonly used version, sha256 is a later and more secure version. Whichever you decide to use is entirely your choice. However, if you are unsure, then it is recommended to use sha256.

The checksum file itself is just a text document that contains a code that should match the code generated by the sha1 or sha256 algorithm. As such, if the code generated from the ISO file matches that contained in the checksum file, then the ISO is fine; otherwise, if the two codes don't match then it means that the ISO file has changed in some way, most likely due to being corrupted. You can think of it like someone using a secret password to identify who they are: if they provide the wrong password, then something is obviously amiss!

Don't worry if this all sounds a bit much, it's actually very straightforward and easy to use!

Checking in Linux

To check the integrity of your downloaded file, it will be necessary to first open the downloaded checksum file using a text editor such as Gedit. Depending on whether you intend to use sha1 or sha256, ensure that you have downloaded and opened the appropriate checksum file, that is one ending in *.sha1sum or *.sha256sum respectively) as they will contain different codes. Once the checksum file has been opened and the code is visible, open up your terminal and change to the directory where your downloaded ISO is stored. For example, if your ISO file is located in the default Downloads folder, you would enter the following command:

user $ cd Downloads COPY TO CLIPBOARD

The command to then perform a checksum uses the following syntax:

[sha1sum or sha256sum] [ISO Image]

For example, the following command will use sha256 to generate a code from the 64 bit Manjaro XFCE 0.8.1 ISO. The code generated can then be compared to the code provided by the appropriate sha256 checksum file:

user $ sha256sum manjaro-xfce-0.8.1-x86_64.iso COPY TO CLIPBOARD

As illustrated, in this instance both codes match, thus confirming that the downloaded ISO file is correct. The following command would use sha1 to undertake exactly the same task:

user $ sha1sum manjaro-xfce-0.8.1-x86_64.iso COPY TO CLIPBOARD

When satisfied that both codes match, then it is safe to proceed to either burning the ISO to your chosen installation media, or using it immediately in Virtualbox. If the codes do not match, then it will be necessary to delete the ISO image and download it again.

Checking in Windows

It will be necessary to download and install a checksum utility application. There are many tools which can provide sha1 and sha256 sums. One such tool is Quick Hash

See Also

• How-to verify GPG key of official .ISO images
• Download Manjaro
• Burn an ISO File
• Installation Guides