How to debug Dracut problems

Foreword

If you are experiencing a problem with system initialization due to Dracut, please see the 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.

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.

= Identifying your problem area =

  Remove  and   from the kernel command line  Add  to the kernel command line. This will present a shell should dracut be unable to locate your root device  Add  to the kernel command line so that dracut shell commands are printed as they are executed  Inspect the debug output generated by the  boot argument with the following commands: 
 * 1) less /init.log
 * 2) 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. ) or from
 * A copy of your disk partition information from
 * A device listing from device-mapper. This can be obtained by running the command
 * A list of block device attributes including vol_id compatible mode. This can be obtained by running the commands  and
 * 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.
 * If you use a dracut configuration file, please include

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:
 * Include volume group information by running the command:
 * Include logical volume information by running the command:

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

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

= Debugging dracut =

Configure a serial console
Successfully debugging dracut will require some form of console logging during the system boot. This section documents configuring a serial console connection to record boot messages. To enable serial console output for both the kernel and the bootloader, follow the procedure below.   Open the file for editing. Below the line timeout=5, add the following: serial --unit=0 --speed=9600 terminal --timeout=5 serial console  Also in, add the following boot arguemnts to the kernel line: console=tty0 console=ttyS0,9600  When finished, the file should look similar to the example below. default=0 timeout=5 serial --unit=0 --speed=9600 terminal --timeout=5 serial console title Fedora (2.6.29.5-191.fc11.x86_64) root (hd0,0) kernel /vmlinuz-2.6.29.5-191.fc11.x86_64 ro root=/dev/mapper/vg_uc1-lv_root console=tty0 console=ttyS0,9600 initrd /dracut-2.6.29.5-191.fc11.x86_64.img 

More detailed information on how to configure the kernel for console output can be found at.

Using the dracut shell
Dracut offers a shell for interactive debugging in the event dracut fails to locate your root filesystem. To enable the shell:
 * 1) Add the boot parameter rdshell to your bootloader configuration file (e.g.
 * 2) Remove the boot arguments rhgb and quiet

A sample bootloader configuration file is listed below.

default=0 timeout=5 serial --unit=0 --speed=9600 terminal --timeout=5 serial console title Fedora (2.6.29.5-191.fc11.x86_64) root (hd0,0) kernel /vmlinuz-2.6.29.5-191.fc11.x86_64 ro root=/dev/mapper/vg_uc1-lv_root console=tty0 rdshell initrd /dracut-2.6.29.5-191.fc11.x86_64.img

If system boot fails, you will be dropped into a shell as seen in the example below. No root device found Dropping to debug shell.

sh: can't access tty; job control turned off

Use this shell prompt to gather the information requested above (see the 'all bug reports' section).

Accessing the root volume from the dracut shell
From the dracut debug shell, you can manually perform the task of locating and preparing your root volume for boot. The required steps will depend on how your root volume is configured. Common scenarios include:
 * A block device (e.g. )
 * A LVM logical volume (e.g. )
 * An encrypted device (e.g. )
 * A network attached device (e.g. )

The exact method for locating and preparing will vary. However, to continue with a successful boot, the objective is to locate your root volume and create a symlink which points to the file system. For example, the following example demonstrates accessing and booting a root volume that is an encrypted LVM Logical volume.

  Inspect your partitions using # parted /dev/sda -s p Model: ATA HTS541060G9AT00 (scsi) Disk /dev/sda: 60.0GB Sector size (logical/physical): 512B/512B Partition Table: msdos

Number Start   End     Size    Type      File system  Flags 1     32.3kB  10.8GB  107MB   primary   ext4         boot 2     10.8GB  55.6GB  44.7GB  logical                lvm  You recall that your root volume was a LVM logical volume. Scan and activate any logical volumes # lvm vgscan  You should see any logical volumes now using the command : # blkid /dev/sda1: UUID="3de247f3-5de4-4a44-afc5-1fe179750cf7" TYPE="ext4" /dev/sda2: UUID="Ek4dQw-cOtq-5MJu-OGRF-xz5k-O2l8-wdDj0I" TYPE="LVM2_member" /dev/mapper/linux-root: UUID="def0269e-424b-4752-acf3-1077bf96ad2c" TYPE="crypto_LUKS" /dev/mapper/linux-home: UUID="c69127c1-f153-4ea2-b58e-4cbfa9257c5e" TYPE="ext3" /dev/mapper/linux-swap: UUID="47b4d329-975c-4c08-b218-f9c9bf3635f1" TYPE="swap"  From the output above, you recall that your root volume exists on an encrypted block device. Following the guidance disk encryption guidance from the Installation Guide, you unlock your encrypted root volume. UUID=$(cryptsetup luksUUID /dev/mapper/linux-root) cryptsetup luksOpen /dev/mapper/linux-root luks-$UUID Enter passphrase for /dev/mapper/linux-root: Key slot 0 unlocked. <li> Next, make a symbolic link to the unlocked root volume ln -s /dev/mapper/luks-$UUID /dev/root <li> With the root volume available, you may continue booting the system by exiting the dracut shell exit </ol>
 * 1) lvm vgchange -ay

Additional dracut boot parameters
The following boot parameters are also available to further assist with debugging boot issues.


 * rdshell : Drop to a shell, if the initramfs fails.
 * rdinitdebug : set -x for the dracut shell.
 * rdbreak=[pre-udev|pre-mount|mount|pre-pivot|] : drop the shell on defined breakpoint
 * rdudevinfo : set udev to loglevel info
 * rdudevdebug : set udev to loglevel debug
 * rdnetdebug : debug network scripts in dracut. Output is written to /tmp