If you are trying to install Ubuntu

1. Ensuring your CD/DVD or USB flash drive burned/written correctly and not damaged:

• How to MD5 test Ubuntu ISOs. See also: Where to find the checksums of Ubuntu ISO images? or MD5 hash for ubuntu .iso (14.04 through 17.04)
• Check out these steps to see how to check your CD once you boot into it to make sure it's ready to go.
• Verify the integrity of the burned CD/DVD or written USB flash drive (this also checks that it's accessible by the computer on which you wish to install).

2. Black/purple screen when you try to boot the LiveCD

The Ubuntu installer's startup portion is sometimes incompatible with certain graphics cards. Fixing it and getting to the Ubuntu Desktop to try or install it can often be surprisingly easy fix: the nomodeset parameter. To see if it works for you:

• Boot from the Desktop Live CD and press the ↓ key when you see the below:

  

• Press Enter and select English:

  

• Press F6, use the ← ↑ → ↓ keys to go down to nomodeset, and press Enter. An x will appear to its left. Then press Esc, and press Enter to "Try Ubuntu without installing."

  

You can also try acpi = off and nolapic if nomodset also shows up as a black screen.

3. Black screen

or

"you need to load kernel first" and "can not read file/cd0" errors

when installing to an UEFI capable machine:

Ubuntu's installer 'when attempting to run in UEFI mode) will hang and stop due to different manufacturer's implementations of the UEFI specification and will hang in different ways. To identify if your machine is booting in installer UEFI mode you will see

REF: UEFI Community Ubuntu Documentation Section 2.4

If your machine is CSM capable (which is a full UEFI implementation with an emulated BIOS layer) after selecting any option from the grub list the system will hang at a black screen.

The picture above actually only confirms your DVD/USB booted using UEFI and there will be some means in firmware settings to ensure drives are booted in order to make the UEFI installer run (a solution may possibly be as simple as ensuring SATA is set to AHCI) - check your vendors manual! Also check the UEFI Community Documentation Section 2.3 for more details.

What you need to do first is to disable SECURE BOOT in the firmware settings. If that does not get the Ubuntu installer running, try disabling anything mentioning UEFI in the firmware settings. Or
If you cannot find UEFI settings then enable CSM - this will disable the UEFI booting of the installer and then allow a legacy/BIOS install of Ubuntu.
Installing grub-efi afterwards will allow UEFI to be re-enabled. Again refer to UEFI Community Ubuntu Documentation at Section 4

Some machines use a full BIOS with an emulated UEFI layer which may throw errors as described ie "you need to load the kernel first" and "can not read file/cd0"

Not all of these machines implement Secure Boot. Simply selecting UEFI in the BIOS settings will configure UEFI mode on hard drives. There is no solution for these errors and the workaround is to disable UEFI to enable the Ubuntu installer to run in legacy mode; after which boot-repair can be used to install grub-efi which then allows/needs UEFI switched back on before Ubuntu will boot using UEFI. Once again refer to the UEFI Community Ubuntu Documentation at Section 4

Black/purple screen after you boot Ubuntu for the first time

This usually happens because you have an Nvidia or AMD graphics card, or a laptop with Optimus or switchable/hybrid graphics, and Ubuntu does not have the proprietary drivers installed to allow it to work with these.

The solution is to boot Ubuntu once in nomodeset mode (your screen may look weird) to bypass the black screen, download and install the drivers, and then reboot to fix it for ever.

• Start your computer, and press the Right Shift when booting up, to get the Grub menu. Use the ← ↑ → ↓ keys to navigate/highlight the entry you want (usually the first one).

  

• Press e to edit that entry, which will show you the details:

  

• Find the linux entry as shown above, use the ← ↑ → ↓ keys to get to it, and then press the End key to get to that line's end (which may be on the next line!).

  

  • Enter nomodeset as shown, and press Ctrl+X to boot to where you can successfully install your graphics drivers.

If you are running Ubuntu 12.04 or 12.10, and have a ATI/AMD graphics card, you have to follow the instructions here, otherwise you will run into this problem every time you restart your computer.

LUKS encryption

In case you've installed Ubuntu with LUKS encryption / LVM option, it could be that Ubuntu just asks you for your password - and you cannot see it. If you have a black screen, try pressing Alt+← and then Alt+→ to switch your tty, this may bring back the password query and turn backlight back on.

If you have a purple screen (maybe you need to set the nomodeset-option also?) and you have encrypted your complete Ubuntu installation, try to just type your encryption/LUKS-password after waiting some seconds (or minutes, just to be sure) and continue with a press on Enter. If this is successfull, you should see your Login-screen just a few seconds later.

1. Try the Alternate Installer - this is a text based installer that might work better than the liveCD depending on your hardware.
   If you do this, you may get a black screen before you even hit grub. A simple Ctrl+Alt+Del gets some users to a usable grub screen

2. If you have an Nvidia Optimus card you should NOT install nvidia drivers, just use the built in driver, see here:

   • Is a NVIDIA GeForce with Optimus Technology supported by Ubuntu?

3. After selecting boot options you have the opportunity to edit the boot flags manually using your keyboard. Replace quiet splash with no splash to get an idea of what step your system is failing at. Using that information search the forums or the internet for answers from the community.

4. If you still can't install Ubuntu then unfortunately you've probably run into a hardware specific bug, please see here: How do I report a bug?

If an update or something else caused your boot problem:

1. Freezes:

   • Freeze troubleshooting at the Ubuntu Wiki
   • Blank Screen troubleshooting at the Ubuntu Wiki

2. nVidia Users:

   • Blank screen after installing nvidia restricted driver
   • Graphics issues after/while installing Ubuntu 16.04/16.10 with NVIDIA graphics

3. ATI/AMD Users:

   • Fglrx causes serious bug-black screen!

4. Grub recovery cross links

   • How to enable boot messages to be printed on screen during boot up?
   • How do I investigate boot and partition issues?

5. Reinstalling your machine

   • I can't boot into a usable system after updates. What should I do?

6. Sometimes a kernel upgrade can cause problems, especially if you're using closed drivers, you can confirm if this is the case by booting into your old kernel.

   • How can I boot with an older kernel version? If your old kernel works then you've found a bug in the new kernel, see the end of this post to report it to the kernel team!
   • Debugging the Kernel Boot at the Ubuntu Wiki

7. LiveCD recovery crosslinks

8. and so on ...
9. If you still can't boot Ubuntu then unfortunately you've probably run into some other kind of bug, please see here: How do I report a bug?

If your graphics card is Nvidia, follow these steps:

1. In the GRUB menu at startup, press e; then,
2. Use the arrow keys to replace quiet splash with no splash or nomodeset.
3. Then press the Ctrl+x key combination to boot.

If your graphics card is ATI, follow these steps:

1. In the GRUB menu at startup, press "e"; then
2. Use the arrow keys to replace quiet splash with radeon.modeset=0.
3. Then press the Ctrl+x key combination to boot.

If your system is dual boot:

Link up the following:

• Boot sector repair

  Boot-Repair

• grub stuff

  Installing and Re-installing GRUB

• If you'd like to totally remove Ubuntu and want to install Windows:

  How to Remove Ubuntu and Put Windows Back On

Increase screen brightness

On certain laptops (like HP Pavilion), you may boot to a black screen due to low screen brightness.

Increase the brightness using key combination (this differs for every model. For example, FN+F7)

It appears as we both share the same hardware. At least the same CPU, The same P67 and the same video card (Mine is a GT 440). What you can do is the following:

1. When booting press the ESC Key or leave the SHIFT key pressed until the GRUB menu appears.

2. In the GRUB menu select the RECOVERY MODE. It should say something like:

   Ubuntu, with Linux 3.2.0-25-generic-pae (recovery mode)

3. After the recovery mode finishes loading, it should present you with a menu. Select the option about going to the shell with root access (root Option. Last option in the image below)

   

4. Now we need to install the Nvidia drivers and update the system. Follow the next lines step by step to do this in the correct order. Also make sure you are connected to the Internet:

   A. Updating System

   1. sudo apt-get update
   2. sudo apt-get upgrade

   B. Nvidia Drivers

   There are 2 ways to install the Proprietary Drivers. the PPA Way or the Default Ubuntu way.

   1. The Default Ubuntu Way involves just typing in the terminal sudo apt-get install nvidia-current (For the current normal drivers) or sudo apt-get install nvidia-current-updates (For the latest current drivers). Just pick one.

   2. the PPA way has the Latest bleeding bloody edge drivers. I mention this one since I am testing it in some use cases that relate to problems using TVs and 16:9/16:10 resolutions. To install this one do this:

      sudo add-apt-repository ppa:graphics-drivers/ppa and press ENTER to accept a message you will receive. Then do sudo apt-get update. Lastly do sudo apt-get install nvidia-375. Note that you can not mix this one with the Ubuntu way. One will overwrite the other one.

5. Reboot sudo reboot

Now if you happen to have any problems do the following via the terminal again but this time go to your home folder. In my case it is /home/cyrex, so I would cd /home/cyrex. In your case you should change that to your user and the apply the following:

sudo rm -fr ./config/monitors.xml
sudo rm -fr .nv*
sudo rm -fr /etc/X11/xorg.conf

Then when you boot into Ubuntu change the resolution via the Displays option in the Ubuntu Settings Menu (The cog in the upper right corner)

What we did there was remove the monitors.xml to solve some resolution problems, remove the .nvidia-settings to fix some Nvidia config problems and remove the xorg.conf (Which is not really needed in the latest Ubuntu versions) to remove any badly configured options.

Lastly we can execute the grub option in the recovery menu to fix any bootloader issues.

I had this problem last night. All of a sudden my system wouldn't boot up anymore. BIOS check would finish, then it would just hang there on a black screen with the cursor flashing. Left it there for several hours just in case. When that didn't work, I unplugged all my USB devices and all of a sudden it booted up fine again. I haven't narrowed it down exactly, but in my case it was either my USB hub or the iPod plugged into that USB hub that was causing it to hang.

Not saying this is necessarily the problem you're having, but hope your boot problem is as easy to fix as unplugging some USB devices...!

If you are using the Windows Installer (Wubi)

Wubi overrides are identical to normal installs except the first time you reboot after running the installer in Windows.

To complicate things, since Ubuntu 11.10 there are two distinct methods to install with Wubi. The first way is using the Desktop ISO, which applies to all sub-flavours (Kubuntu, Lubuntu, Mythbuntu etc.) and also if you downloaded the Ubuntu ISO yourself.

The second method is using a pre-installed disk-image, if you run wubi.exe standalone and choose to install Ubuntu.

Method 1

You'll see this:

Completing the Ubuntu installation
For more installation options, press ESC now 5...4...3...2...1

Press Esc and then you see this:

Normal mode
Safe graphic mode
ACPI workarounds
Verbose mode
Demo mode

Ignore Safe graphic mode as it applied to Ubuntu in 2008 and does nothing for the modern nvidia/radeon issue. Place your cursor on Normal mode and press E. Then edit the entry and insert nomodeset as shown here (look for it between noprompt and quiet splash in the middle; note there may be some other differences but don't change anything else - just add nomodeset):

linux /ubuntu/install/boot/vmlinuz debian-installer/custom-installation=/ubuntu/install/custom-installation 
iso-scan/filename=/ubuntu/install/installation.iso 
automatic-ubiquity noprompt nomodeset quiet splash boot=casper ro debian-installer/locale=en_US.UTF-8 
console-setup/layoutcode=us console-setup/variantcode= -- rootflags-syncio
initrd /ubuntu/install/boot/initrd.lz

Now press Ctrl+X to boot.

NOTE: This only applies to the Installation; the next time you boot you have to override it again, and for this it will be the same as for a normal install (answered above). Make sure you hold Shift to make the Grub menu show though.

Method 2 When you run wubi.exe standalone and install Ubuntu (not a sub-flavour), it downloads a pre-installed, compressed disk image with a default Ubuntu install, and then decompresses this to the size of the virtual disk. There is no grub.cfg setup yet so it uses the file \ubuntu\install\wubildr-disk.cfg for the first boot which you can edit and add nomodeset:

loopback loop0 /ubuntu/disks/root.disk
set root=(loop0)
search --set=diskroot -f -n /ubuntu/disks/root.disk
probe --set=diskuuid -u $diskroot
linux /vmlinuz root=UUID=$diskuuid loop=/ubuntu/disks/root.disk preseed/file=/ubuntu/install/preseed.cfg wubi-diskimage ro quiet splash nomodeset
initrd /initrd.img
boot

Note - if you've come to this thread after booting for the first time, it's possible that the grub.cfg has already been created (even if it froze up). In this case, editing the \ubuntu\install\wubildr-disk.cfg file will do nothing - it always checks for /boot/grub/grub.cfg inside the virtual disk first. So you should follow the instructions for the normal install above.

Note also that the Grub Menu is suppressed by default on Wubi installs (even though there are two operating systems - because you boot Ubuntu from Windows, and therefore adding a Windows entry from Ubuntu's Grub Menu makes no sense) so you have to press and hold the Shift key after selecting Ubuntu in order to display the Grub Menu. On Windows 8, it reboots after you elect to boot into Wubi, in which case, you should hold the Shift key after the BIOS posts.
(This is only for Windows 8 with BIOS - Wubi doesn't work with UEFI).

I also had this problem, or a similar one. It turned out that, for some reason, Ubuntu had started with the screen brightness on its lowest setting. If I went into a very dark room, I could see the screen just well enough to go to the "Brightness and Lock" control panel and turn the brightness up to where it should be.

how to fix :

1. Start ubuntu, login, now in the blackscreen go to the console Ctrl+Alt+F1 and type nautilus

2. if nautilus cannot be opened in terminal type unity

3. now without exiting or stoping the unity comand return to the ubuntu interface in my pc is Ctrl+Alt+F7
4. open terminal in nautilus using Ctrl+Alt+T and type nautilus
5. while nautilus still open, in terminal type sudo software-properties-gtk
6. search for graphic drivers, my problem was the default drivers of X.org. I have an ati video card and I installed the drivers of fglrx-updates if you have nvidia install the drivers of nvidia or if you have ati driver
7. reboot
8. after login u will see nautilus running well and the wallpaper the only thing not working is unity. open terminal and type: dconf reset -f /org/compiz/ and setsid unity

thats it.

I hope this fix your problem.