Among all the new bells and whistles coming with the latest major release of RedHat Enterprise Linux platform, resolution bot both the installation process and system console have changed (higher resolution than before is default).
Unfortunately, server system does not necessarily have the newest display device or iLO, iDRAC and virtual machine consoles are out of range for these high resolutions.
It is fortunately possible to lower the resolution that will fit your console or screen.
1. To lower the resolution at installation process, simply press “TAB” at the installer boot menu, you will see a line appearing at the bottom of the screen with the following :
> vmlinuz initrd=initrd.img inst.stage2=hd:LABEL=CentOS\x207\x20x86_64 quiet
All you have to do is adding a space and append “resolution=” or “vga=” with the desired value as followed :
resolution=640x480
Alternatively, you can enter the VGA color code by entering “vga=” followed by the colour code (example : vga=785). See the chart below for more informations :
| Color depth | 640×480 | 800×600 | 1024×768 | 1280×1024 | 1400×1050 | 1600×1200 |
| 8 (256) | 769 | 771 | 773 | 775 | ||
| 15 (32K) | 784 | 787 | 790 | 793 | ||
| 16 (65K) | 785 | 788 | 791 | 794 | 834 | 884 |
| 24 (16M) | 786 | 789 | 792 | 795 | ||
2. At the boot process of the system, you will need to edit the Grub2 boot loader by pressing “e” at boot at the kernel selection screen and edit the “vmlinuz” line, append at the end of the line “video=” followed by the desired resolution such as :
video=640x480
Then press CTRL + X to boot.
You may make this change permanent by editing the Grub configuration. Follow the instructions of the following article : Edit Grub2 settings on RHEL/CentOS 7
NOTE : The lowest resolution supported by RHEL 7 console and installer is 400 x 375.