Basic Fedora Troubleshooting

I assume you are smart enough to wear eye protection and a dust mask when blowing compressed air through a PC. That just makes basic sense, right?

In any case, you are reading and performing these steps at your own risk. Don't touch any wires, etc. if you are not comfortable with your own skill set.

Always review the Fedora Installation Guide, the Fedora Common Problems, and the Kernel Problems before installing Fedora.

If you are suffering from kernel instability and random crashes, especially read the 'Kernel Problems'.

Dealing with Display Failures After a Fresh Install

X11 is the basic graphical display system in Linux. Fedora usually installs fine on most hardware, but occasionally there are problems with the display. I've prepared a set of screen shots that show how to 'rescue' a Fedora system so you can log into the desktop using a generic 'frame buffer' video driver. Fedora switches video modes in several places, so we'll avoid that wherever possible.

Dealing with the grub> prompt after a hardware change or a Fresh Install

Grub is the bootloader. It is common to get a basic grub> prompt after a hardware change or fresh install, so I've created a series of screen shots to step you through the process of reconfiguring the grub bootloader from the initial boot screen.

If you've tried the offical 'Fedora Kernel Problems' and are still seeing instability

Consider running Memtest86 and/or Damn Small Linux as troubleshooting tools (see below) to validate your hardware.

Testing the proprietary ATI Radeon Catalyst 8.9 Driver

The Catalyst 8.9 driver and Fedora 9. The X server crashes, and I don't want to downgrade to the Fedora 8 version, I'd rather wait for now. Here is the README if you would like to duplicate my results or review the patch. Note that this is alpha and I can't guarantee the RPM install/remove won't foul your system. Use at your own risk.

Previous test of ATI's Catalyst 8.8 Driver

The Catalyst 8.7 driver and Fedora 9. The X server crashes, and I don't want to downgrade to the Fedora 8 version, I'd rather wait for now. Here is the README if you would like to duplicate my results or review the patch. Note that this is alpha and I can't guarantee the RPM install/remove won't foul your system. Use at your own risk.

Previous test of ATI's Catalyst 8.7 Driver

The Catalyst 8.7 driver and Fedora 9. The X server crashes, and I don't want to downgrade to the Fedora 8 version, I'd rather wait for now. Here is the README if you would like to duplicate my results or review the patch. Note that this is alpha and I can't guarantee the RPM install/remove won't foul your system. Use at your own risk.

NVIDIA owners : I installed the NVIDIA *Beta* driver (177.13) at work (Quadro card) and it appears stable. TwinView is up.

I want to install Fedora but when I push the power button there is no fan or lights

1. Has the machine ever successfully booted? When?
2. Has the machine been crashing in recent weeks/days?
3. Is it plugged in?
4. Is the wall power good (try a lamp, hand drill, etc for power)
5. If the machine will not power up to a good power source, consult the manual for a troubleshooting guide
6. If the machine is used and will not power up, have you added any hardware to prepare for linux? Perhaps a cord or power connection is loose in the case, or a plug-in card is improperly seated.
7. If you get here, it is likely your machine will need to be repaired before installing linux
8. If you are comfortable working on PCs consider blowing the dust out of all areas of your PC
9. If you are comfortable working on PCs consider diassembling/reassembling all components in the case
10. If there is no fan, light, etc. the power supply may be a good starting point. Consider replacing the power supply first
11. Note that many PC type power supplies (switching power supplies) will not turn on unless they are plugged into a motherboard. Don't get stuck in the trap of thinking a PC power supply is bad because the fan won't spin when you plug it in.

I want to install Fedora but when I push the power button I see lights flash or hear a fan, but nothing is on the display

1. Is the display known good? Is the display cable properly plugged in?
2. Has the machine ever successfully booted anything?
3. Has the machine been crashing in recent weeks/days?
4. Does any of the BIOS Logo or POST text appear on the display?
5. If you get a BIOS POST and a message like "No boot device found, hit F1 to retry" consider entering the BIOS and insuring the machine is setup to boot from your boot media (a hard drive or CDROM/DVD reader) first.
6. If there is no BIOS POST consult the manual for a troubleshooting guide
7. If there is no BIOS POST, have you added any hardware to prepare for linux? Perhaps a cord or power connection is loose in the case, or a plug-in card is improperly seated.
8. If you get here, it is likely your machine will need to be repaired before installing linux
9. If you are comfortable working on PCs consider the section above for a dead PC. Consider opening the case and blowing out the dust, reseating cards, cables, etc.

I want to install Fedora but after the BIOS POST the CDROM flashes and then nothing else happens.

1. Make sure you have not mistakenly placed a bootable DVD in a CDROM only drive
2. Make sure your writer/media/reader are compatible. For example DVD+R/W media might write fine in one drive, but be unreadable in another
3. Attempt to boot from a CDROM that is known good, or test your Fedora DVD and/or CDROM media on another machine to make sure it is bootable
4. If you definitely can boot CDROM media, consider exercising your system with Damn Small Linux or Memtest86+ (see links above)
5. Check the output of the 'dmesg' command after booting from D-S-L. Verify your DVD media is compatible with your reader
6. Check the make/model of your DVD writer and reader. Check their firmware levels. Old readers, even listed as 'DVD+R/W', sometimes cannot read DVD+R/W media without a firmware update
7. Verify your hardware. Run D-S-L for a couple of hours and Memtest86+ for 6 hrs. or so
8. If you added a new DVD/CDROM or hard drive to your system, and they are PATA on the same cable, check your Master/Slave select
9. If your machine cannot boot and run the Damn Small Linux CDROM or a Memtest86+ CD, your CDROM/DVD reader may be broken
10. If nothing will boot from your CDROM, your machine is broken or misconfigured and must be configured properly or repaired
11. If you are comfortable working on PCs consider the section above for a dead PC. Consider opening the case and blowing out the dust, reseating cards, cables, etc.

I want to install Fedora, but all I have is a CDROM reader, not a DVD reader

1. Fedora provides a 'Network Install' CDROM iso. Some versions of Fedora call this a 'Rescue CD'. You can use this to perform a network install
2. Network installs involve booting from the CDROM and tapping a key at the splash image. You should see a 'boot:' prompt
3. Once you have a 'boot:' prompt, type 'linux askmethod' then press the <enter> key
4. Note : A network install will probably work best over an instranet or local lan, where you have a server handy to host the Fedora repositories locally, or the DVD install image.
5. See the link below for more details about HTTP network installs

I want to install Fedora, and my BIOS supports PXE, and I have no CDROM or DVD reader

1. PXE installs require a server on your lan, running the 'tftp' service, in addition to your install client.
2. You should probably google for how to setup tftp, but here are a few hints
3. --later versions of fedora host tftp below /var/lib/tftpboot
4. --your /etc/xinetd.conf on the server needs to have 'enabled = tftp' and 'disabled = no'
5. --obviously xinetd needs to be enabled and running on the server...
6. --your intranet dhcp server needs to tell the client machine where the tft server is and what file to boot
7. --once you get the "Fedora Rescue" image or "Network Install" image booted, it's the same as a normal CDROM network install, meaning somewhere on your intranet/lan you will be hosting either a repository or the Fedora DVD iso image

Fedora installed ok but when I reboot nothing happens

1. Nothing as in no fan or lights?
2. Nothing as in fan only, or a lamp, and no BIOS messages?
3. Nothing as in a BIOS prompt similar to "Cannot boot. Hit F1 to continue..."?
4. Nothing as in you see the grub> prompt and that's it?
5. Nothing as in linux boots, but the screen goes black?
6. Nothing as in linux boots for a bit, shows the "Entering Interactive Mode", then hangs in udev?

Items 1) and 2) require going up to the top of the document.

Item 3) requires entering the system BIOS and checking your boot order, and that the BIOS sees your hard drive.

Item 4) requires either learning how the grub shell works (top of page) or attempting to use the Fedora Rescue CD and performing a change-root, then grub re-install.

Item 5) requires trying two different things. One is booting the kernel without 'rhgb', the second is editing the xorg.conf and trying an alternate driver. See the 'alternate video mode' section below.

Item 6) indicates a driver is improperly probing a hardware device as part of the udev process. This requires adding kernel options to the grub kernel boot line, for troubleshooting, as the system starts. See the 'Fedora Common Problems', and 'KernelCommonProblems' near the top of the page, and my 'Booting with kernel options' below. Consider the following list, which has dug me out of a few crashed systems :

1. Search google or the manufacurer's site for Linux issues
2. A common fix is to go into the system BIOS and disable a chipset you are not using
3. To get a hint about the problem, add the 'initcall_debug' to the kernel options and and hope to see the crash info
4. Sometimes the kernel will print messages with the name of the driver that is fouling the kernel.
5. Using the kernel messages, the search info, and the BIOS and motherboard docs, you might be able to determine the offending chip, then disable the chip in the BIOS
6. Once your system boots past udev, you can update your system ('yum update') and retry the chipset.
7. If updates don't help, another option is to blacklist the module in /etc/modprobe.d/blacklist
8. Blacklisting modules is useful because you have the chip enabled and the kernel running. This is really great if you are looking to try driver source code from the web and load the module yourself>
9. Sometimes another version of linux (different kernel) will boot ok. Try 'Damn Small Linux' (top of page). Sometimes this ability to get to the command prompt lets you do things like look at the /var/log/messages for warnings about PCI devices, or the output of the 'lspci' command will help you identify a problem driver or chipset.

Booting with kernel options:

1. Check the Kernel Problems link at the top of this page, and note which options you want to try
2. Press any key (e.g; space bar) at the Fedora menu it times out.
3. Use the Up/Down arrows to select the Fedora boot option of your choice (in your case there may be only one choice) then 'e' to edit.
4. Use the Up/Down arrows to select 'kernel' line then 'e' to edit
5. The kernel line should say something like 'kernel ... rhgb quiet'. Add options like 'noapic' etc. per the Kernel Problems, then the 'enter' key to accept the new line.
6. Finally 'b' to boot the kernel with the new options.

Booting without rhgb:

1. See 'Booting with kernel options' above.
2. Note that rhgb can crash some systems. Unfortunately, so can the 'vga=791' option. 'vga=1' almost never crashes systems.
3. Remove 'rhgb' and 'quiet'. Optionally, add 'vga=791' (or 'vga=1')
4. Use 'enter' key to finish the edit, then 'b' for boot.

Note : once you find a set of kernel options that work, you can edit the file /etc/grub.conf and make your changes permanent. Find the kernel line in the file and change it with your preferred options. See the next section on editing a file.

Trying an alternate video mode and driver:

1. There are two parts to this...one, the graphical boot, and two, the system graphical desktop. First, the graphical boot. This affects the boot screen. Sometimes this helps avoid things wrapping off the side of the display (it's a 120 column display rather than 80). If 'vga=791' crashes your kernel, just leave it off, or use 'vga=1'
2. Edit the boot kernel line to go into single user mode (Similar to 'Booting without rhgb' (above))
3. Remove 'rhgb' and quiet' then add 'vga=791' and 'single'. Alternatvely, use 'vga=1'
4. Press 'enter' key to finish the edit, then 'b' for boot. Expect a '#' prompt momentarily
5. Now we adjust the graphical desktop driver. This affects the actual driver in runlevel 5, the GUI with menus, windows, etc. Sometimes this helps avoid locks and distorted video displays
6. # cd /etc/X11
7. # nano xorg.conf
8. Change the 'Driver' in the 'Device' section to 'vesa'
9. Save the file and exit nano. You could use 'vi' also, whatever editor you prefer.
10. # exit

Your system should now use the vesa driver rather than the Fedora configured driver. This is a fairly safe, but low performance, driver. Every once in awhile, for example after a set of updates, you should try to switch back to the normal/native driver for your video chipset to see if the problem is fixed. The performance and appearance is usually much better when using a native chipset driver (like 'radeon' or 'nv').

Trying alternate video frequencies:

1. Sometimes this helps fix issues with incorrect displays like torn/jagged/unreadable graphical desktops.
2. Edit the boot kernel line to go into single user mode (Similar to 'Booting without rhgb' (above))
3. instead remove 'rhgb' and 'quiet' then add 'vga=791' (or 'vga=1') and 'single'
4. 'enter' key, then 'b' for boot. Expect a '#' prompt momentarily
5. # system-config-display --help
6. Consult the manual for your display to find the proper horizontal and vertical video frequency limits. You can specify them using the system-config-display command. Alternatively, you can google the internet for samples of how to set the values in the /etc/X11/xorg.conf file. Then edit the file with 'vi' or 'nano' to set or change the values.
7. # exit

Updating a broken system:

1. Edit the boot kernel line to go into single user mode (Similar to 'Booting without rhgb' (above))
2. instead remove 'rhgb' and 'quiet' then add 'vga=791' (or 'vga=1') and 'single'
3. 'enter' key, then 'b' for boot. Expect a '#' prompt momentarily
4. # /etc/init.d/network start
5. The networking interface should come up (green PASS). If not check the cables, etc. for your network
6. "Yum Update" the system.
7. # yum update
8. This downloads all the patches for your system. Perhaps it will fix a driver or other problem. This can take a while...
9. # reboot
10. Hopefully your system will reboot and work better.

When posting questions to the Fedora Forum about broken machines or Fedora installs, please add a few notes about:

1. The machine's history; e.g; new or used
2. When last sucessfully booted, and against which O/S?
3. What was the last H/W change, and what was changed (if applicable)
4. Has the system been tested against Memtest86+?
5. Has the system been tested against Damn Small Linux?
6. Have the various Fedora recommended kernel options been tried? Did they help?
7. If the machine is booting to a black screen, did eliminating 'rhgb' help? Did the 'vesa' driver change help?