Creazione e utilizzo di un’immagine di installazione live

Lo strumento ufficiale e supportato per creare una pennetta USB Fedora è l’utilità Fedora Media Writer, precedentemente nota come LiveUSB Creator. Vedere la guida Fedora Media Writer nella panoramica della documentazione utente di Fedora.

Questo metodo è per persone che utilizzano Linux, o un qualsiasi altro unix con GNOME, Nautilus e l’Utilità dei dischi GNOME installata. In particolare, se si sta utilizzando una distribuzione diversa da quella di Fedora che non supporta Flatpak, questo potrebbe essere il metodo facilmente più disponibile. Utenti di un’installazione standard di Fedora, o di un’installazione standard di GNOME delle altre distribuzioni, dovrebbero essere in grado di seguire questo metodo. Su Fedora, assicurarsi che i pacchetti nautilus e gnome-disk-utility sono installati. Potrebbero essere disponibili strumenti simili grafici di scrittura diretta in altri ambienti, oppure utilizzare la riga di comando per il metodo della scrittura diretta.

UNetbootin è un creatore grafico di immagini USB avviabili. Usandolo permetterà di preservare qualsiasi dato presente sull’unità USB. Se si hanno problemi di avvio, tuttavia, si potrebbe voler provare con un’unità vuota, formattata in modo pulito in FAT32.

Se si sta già eseguendo un CD live, DVD o USB e si vuole convertire quello in una pennetta USB avviabile, eseguire il seguente comando:

La maggior parte dei metodi di scrittura richiederà di conoscere il nome /dev per la pennetta USB, ad es. /dev/sdc, quando li si usa su Linux. Non è necessario sapere questo per usare Fedora Media Writer. Per scoprirlo:

Si può testare la pennetta usando QEMU.

Si può usare lo script liveimage-mount nel pacchetto livecd-tools per montare un dispositivo USB Live attaccato o altra immagine LiveOS, come un ISO o CD Live. Questo è conveniente quando si vuole copiare dentro o fuori qualche file dal filesystem LiveOS su una USB Live, o semplicemente esaminare i file in un ISO Live o CD Live.

To create a live image, the livecd-creator and mock packages are used. For this, super user privileges are needed.

The livecd-creator tool is part of the _livecd-tools_package. If it is not installed on your system, add it and all other tools like mock, lorax, git, pykickstart and a text editor with DNF:

Hint: We are creating a livecd like the fedora-live-workstation image, which is totally localized, but has english as default. There is no need to install any localization support on your own. You can change it in the created kickstart.cfg if necessary.

We need to add you current user to the mock group, or you need to do anything as root user.

The $(whoami) adds your current user, as we do not know what username you are currently using ;)

A relogin to make the change effective, would be wise, or you switch to root now.

Let’s create the mock group:

If you now enter:

it shall output your username together with the old groups and the new group "mock". If this is not the case, you did something wrong.

Now we can init the build environment. In this example we use the most likely x86_64, but if you build it for ARM or PowerPC, you can just use a different config by changing the ARCH-Type to the desired plattform!

Mock creates us an empty toolbox for this, so we need to fill it with packages, which we will need to create the image later in the process. If you now think "Why so complicated?" you are only partly right, as a toolbox is a simple container, which we need to seperate the work for different releases of Fedora, otherwise you have to overwrite and mixing different builds on your own.

Make sure you have enogh free disk space for all these files and the ones, the livemedia-creator will download later. We suggest at least 10 GB free diskspace for this.

If you wanne use a different texteditor then "vim", you need to install it now, otherwise you are stuck to a not so well integrated basic "vim" installation, which will be a bit unpleasent to use. Don’t panic, we don’t do much editing inside the toolbox, vim will do :)

Now we enter the toolbox for the first time …​

This gives us a shell and networksupport, so the scripts inside the toolbox can access the internet and install packages from the repo.

You will see something like this output:

Now we need to download the kickstart files, which previouse Fedora releases had as a package, from the Fedora Servers:

You can access the page with a normal browser, to see which tags aka 'branches' like "f42" are available, in case you wanne do another version. What happens now is a git checkout into the current directory of your toolbox. Big advantage: no danger of overwriting files on your os.

ATTENTION: before you continue, make sure you have at least 10 GB of free storage on your systems partition as we will download a lot of rpms and create an image that is at least 2,3 GB in size. If you don’t have enough space, all future steps can faill with the wildest error messages and your will waste A LOT of time with it!

What we now need is a kickstart file. Never heared of it, don’t panic :D

A kickstart file contains informations about the size of the tmp drive in the later started live image, it mounts, its packages and so on. You will not need to reinvent the wheel, relax. Here is an example:

What you see is a subsection of all possible options, because that git checkout before, downloaded a full set of already working kickstart files, which we will join up to one new kickstart.cfg file.

The above file will remove packages and groups of packages from the later created image, compared to the normal Fedora-Live-Workstation image. We call this a DELTA-file, because we just define the differences between our image and the original Fedora Live Workstation image.

You see this:

This includes the original kickstart (ks) config for the original Fedora-Live-Workstation Image as a base file. The rest of the lines "overwrite" the sections in the original file. So you just tell kickstart what you want and not want compared to the Fedora-Live-Workstation image.

In this example, we removed some gnome-apps and end up what you know as "Fedora-Minimal-Workstation" Image.

Take that example and save it to a file you can name i.E. "example-START.ks". Make sure you can distingish your file later as the starting point of your work. Because now, we will "join" aka. "flatten" the included files to one big kickstart.cfg file, that we will need for livemedia-creator later.

The problem you are now facing is, it doesn’t work out-of-box, because ksflatten does not find all the includes it needs. You can solve this in two ways:

a) you move your ks file to the directory named "fedora-kickstarts" and switch to it with cd, or

b) you execute the above command and copy all files it names in the errormessage from "fedora-kickstarts" to "." untill it stops complaining.

From now on, you should only edit the created kickstart.cfg file for changes, otherwise you have to repeat the next step over and over again.

Either way, you end up with a defective cfg file, because the used include files define the mountpoint "/" two times, which lead to an error. That’s easily fixed:

search for "# Disk partitioning information" and change the two lines, that start with "part /" to this ONE line:

We will try to fix this, but it could take until Fedora 45.

Now the part you are waiting for: Let’s create the iso image.

Please replace the folling terms:

"MYPROJECTNAME" That is your internal project name, that ends up in /etc/os-release "MY_ID" that is the name of the mounted ISO file AND VERY IMPORTANT if you wanne refer to that iso in GRUB "<FILENAME>" thats the name of the created iso file unter /var/lmc

In approximitly 15 minutes, if everything works, you have a created <filename>.iso image IN YOUR TOOLBOX.

To get it out there, you enter …​

and copy it to the desired place. In example:

Now you can test your image in different ways:

a) you can use Gnome-Boxen to just run it in your desktop environment, which is way easier.

or

b) use the QEMU line in the next section.

Congratulations: You are done creating our own live-image. Some tips on the way:

Come root:

Sostituire filename.iso con il nome dell’immagine CD Live creata e qemu-system-x86_64 con un binario qemu appropriato per il sistema target, ad es. qemu-system-i386.

L’immagine live può incorporare funzionalità per verificare se stessa. Per farlo, è necessario avere isomd5sum installato sia sul sistema usato per creare l’immagine che installato nell’immagine. Questo in modo che le utilità implantisomd5 e checkisomd5 possano essere usate. Queste utilità sfruttano l’incorporamento di un md5sum nell’area applicazione dell’immagine iso9660. Questo viene poi verificato prima di montare il filesystem root reale.