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| {{How_to_debug2 | | {{How_to_debug2 |
| |component=Dracut | | |component=Dracut |
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| | |problem_area=# Remove ''rhgb'' and ''quiet'' from the kernel command line |
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| '''Foreword'''
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| If you are experiencing a problem with system initialization due to [[Dracut]], please see the [[Bugs/Common|common bugs]] document before filing a bug. Some easy configuration tweaks that fix a wide range of issues may be listed there. If the problem you are seeing is not listed there or none of the workarounds seem to help, please consider filing a bug to help us make Fedora run better on your hardware.
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| Be prepared to include some information (logs) about your system as well. These should be complete (no snippets please), not in an archive, uncompressed, with MIME type set as text/plain.
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| = Identifying your problem area = | |
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| # Remove ''rhgb'' and ''quiet'' from the kernel command line | |
| # Add ''rdshell'' to the kernel command line. This will present a shell should dracut be unable to locate your root device | | # Add ''rdshell'' to the kernel command line. This will present a shell should dracut be unable to locate your root device |
| # Add ''rdshell rdinitdebug'' to the kernel command line so that dracut shell commands are printed as they are executed | | # Add ''rdshell rdinitdebug'' to the kernel command line so that dracut shell commands are printed as they are executed |
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| #:<pre># less /init.log</pre> | | #:<pre># less /init.log</pre> |
| #:<pre># dmesg | less</pre> | | #:<pre># dmesg | less</pre> |
| | | |report_info= |
| = Information to include in your report = | |
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| {{Anchor|AllInfo}}
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| == All bug reports == | | == All bug reports == |
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| {{Anchor|Debugging}} | | {{Anchor|Debugging}} |
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| = Debugging dracut =
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| == Configure a serial console ==
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| Successfully debugging dracut will require some form of console logging during the system boot. This section documents configuring a serial console connection to capture boot messages.
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| # First, enable serial console output for both the kernel and the bootloader.
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| #* Open the file {{filename|/etc/grub.conf}} for editing. Below the line ''timeout=5'', add the following:
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| #*: <pre>serial --unit=0 --speed=9600
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| #*: terminal --timeout=5 serial console</pre>
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| #* Also in {{filename|/etc/grub.conf}}, add the following boot arguemnts to the ''kernel'' line:
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| #*: <pre>console=tty0 console=ttyS0,9600</pre>
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| #* When finished, the {{filename|/etc/grub.conf}} file should look similar to the example below.
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| #*:<pre>
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| #*:default=0
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| #*:timeout=5
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| #*:serial --unit=0 --speed=9600
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| #*:terminal --timeout=5 serial console
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| #*:title Fedora (2.6.29.5-191.fc11.x86_64)
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| #*: root (hd0,0)
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| #*: kernel /vmlinuz-2.6.29.5-191.fc11.x86_64 ro root=/dev/mapper/vg_uc1-lv_root console=tty0 console=ttyS0,9600
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| #*: initrd /dracut-2.6.29.5-191.fc11.x86_64.img</pre>
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| #* More detailed information on how to configure the kernel for console output can be found at [http://www.faqs.org/docs/Linux-HOWTO/Remote-Serial-Console-HOWTO.html#CONFIGURE-KERNEL].
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| {{admon/tip|Redirecting non-interactive output|You can redirect all non-interactive output to /dev/kmsg and the kernel will put it out on the console when it reaches the kernel buffer by doing
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| <pre>exec >/dev/kmsg 2>&1 </dev/console</pre>}}
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| == Enable the dracut debug module ==
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| To turn on dracut debugging, you must rebuild the dracut initial ramdisk with the appropriate parameter. The following commands demonstrate rebuilding the ramdisk with the ''debug'' dracut module enabled.
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| # Create a dracut ramdisk image with debugging enabled
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| #: <pre>dracut -a debug /boot/initrd-debug-$(uname -r).img $(uname -r) </pre>
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| # Next, tell your bootloader to use the new dracut ramdisk
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| #: <pre>grubby --make-default --title "Debugging dracut" \
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| #: --add-kernel /boot/vmlinuz-$(uname -r) \
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| #: --initrd /boot/initrd-debug-$(uname -r).img \
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| #: --copy-default</pre>
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| # When ready to debug dracut, reboot the system
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| == Using the shell ==
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| Dracut offers a shell for interactive debugging in the event dracut fails to locate your root filesystem. To enable the shell:
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| # Add the boot parameter ''rdshell'' to your bootloader configuration file (e.g. {{filename|/etc/grub.conf}}
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| # Remove the boot arguments ''rhgb'' and ''quiet''
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| A sample {{filename|/etc/grub.conf}} bootloader configuration file is listed below.
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| <pre>default=0
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| timeout=5
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| serial --unit=0 --speed=9600
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| terminal --timeout=5 serial console
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| title Fedora (2.6.29.5-191.fc11.x86_64)
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| root (hd0,0)
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| kernel /vmlinuz-2.6.29.5-191.fc11.x86_64 ro root=/dev/mapper/vg_uc1-lv_root console=tty0 console=ttyS0,9600 rdshell
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| initrd /dracut-2.6.29.5-191.fc11.x86_64.img</pre>
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| If system boot fails, you will be dropped into a shell as seen in the example below.
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| <pre>
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| No root device found
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| Dropping to debug shell.
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| sh: can't access tty; job control turned off
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| #
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| </pre>
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| Use this shell prompt to gather the information requested above (see [[How_to_debug_Dracut_problems#AllInfo|the 'all bug reports' section]]).
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| == Additional dracut boot parameters ==
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| The following boot parameters are also available to further assist with debugging boot issues.
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| ; rdshell : Drop to a shell, if the initramfs fails.
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| ; rdinitdebug : set -x for the dracut shell.
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| ; rdbreak=[pre-udev|pre-mount|mount|pre-pivot|] : drop the shell on defined breakpoint
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| ; rdudevinfo : set udev to loglevel info
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| ; rdudevdebug : set udev to loglevel debug
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| ; rdnetdebug : debug network scripts in dracut. Output is written to /tmp
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| [[Category:Debugging]] [[Category:How to]]
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This page describes how to debug Dracut. For general information on how to file a bug, should you need to do so, please see Bugs and feature requests.
Identifying your problem area
- Remove rhgb and quiet from the kernel command line
- Add rdshell to the kernel command line. This will present a shell should dracut be unable to locate your root device
- Add rdshell rdinitdebug to the kernel command line so that dracut shell commands are printed as they are executed
- With dracut >= 002-11 [1], you can inspect the rdinitdebug output with:
# less /init.log
# dmesg | less
Information to include in your report
All bug reports
In all cases, the following should be mentioned and attached to your bug report:
- The exact kernel command-line used. Typically from the bootloader configuration file (e.g.
/etc/grub.conf) or from /proc/cmdline
- A copy of your disk partition information from
/etc/fstab
- A device listing from device-mapper. This can be obtained by running the command
dmsetup ls --tree
- A list of block device attributes including vol_id compatible mode. This can be obtained by running the commands
blkid and blkid -o udev
- Turn on dracut debugging (see the 'debugging dracut' section), and attach all relevant information from the boot log. This can be obtained by running the command
dmesg|grep dracut.
- If you use a dracut configuration file, please include
/etc/dracut.conf
Logical Volume Management related problems
As well as the information from the 'all bug reports' section, include the following information:
- Include physical volume information by running the command:
lvm pvdisplay
- Include volume group information by running the command:
lvm vgdisplay
- Include logical volume information by running the command:
lvm lvdisplay
Software RAID related problems
As well as the information from the 'all bug reports' section, include the following information:
- If using software RAID disk partitions, please include the output of
/proc/mdstat
Network root device related problems
This section details information to include when experiencing problems on a system whose root device is located on a network attached volume (e.g. iSCSI, NFS or NBD). As well as the information from the 'all bug reports' section, include the following information:
- Please include the output of
ip addr show
