Salve a tutti, ho scaricato il DVD di CentOS-7 e l'ho messa su chiavetta con Rufus. Il problema sorge quando la la avvio dal BIOS e dopo un po' che carica escono queste righe (non mi faceva caricare la foto quindi le ho trascritte):

[   10.221742] sd 0:0:0:0: [sdb] No Caching mode page found
[   10.221811] sd 0:0:0:0: [sdb] Assuming drive cache: write through
     Mounting Configuration File System...
[   OK   ] Started Show Plymounth Boot Screen.
[   OK   ] Reached target Paths.
[   OK   ] Reached target Basic System.
[   OK   ] Mounted Configuration File System.
dracut-initqueue[597]: Warning: Cloud not boot.
     Mounting Configuration File System...
[   OK   ] Started Show Plymounth Boot Screen.
[   OK   ] Reached target Paths.
[   OK   ] Reached target Basic System.
[   OK   ] Mounted Configuration File System.
dracut-initqueue[597]: Warning: Cloud not boot.
dracut-initqueue[597]: Warning: /dev/root does not exist
     Starting Dracut Emergency Shell...
Warning: /dev/root does not exist

Generating "/run/initramfs/rdsosreport.txt"

Entering emergency mode. Exit the shell to continue.
Type "journalctl" to view system logs.
You might want to save "/run/initramfs/rdsosreport.txt" to a USB stick or /boot
after mounting them and attach it to a bug report.

dracut:/#