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 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
blkidandblkid -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
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
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
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
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.
- First, enable serial console output for both the kernel and the bootloader.
- Open the file
/etc/grub.conffor editing. Below the line timeout=5, add the following:serial --unit=0 --speed=9600
- terminal --timeout=5 serial console
- Also in
/etc/grub.conf, add the following boot arguemnts to the kernel line:console=tty0 console=ttyS0,9600
- When finished, the
/etc/grub.conffile 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 [2].
- Open the file
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
exec >/dev/kmsg 2>&1 </dev/console
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:
- Add the boot parameter rdshell to your bootloader configuration file (e.g.
/etc/grub.conf - Remove the boot arguments rhgb and quiet
A sample /etc/grub.conf 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.
/dev/sda7) - A LVM logical volume (e.g.
/dev/VolGroup00/LogVol00) - An encrypted device (e.g.
/dev/mapper/luks-4d5972ea-901c-4584-bd75-1da802417d83) - A network attached device (e.g.
netroot=iscsi:@192.168.0.4::3260::iqn.2009-02.org.fedoraproject:for.all)
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 /dev/root 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- 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
- lvm vgchange -ay
- You should see any logical volumes now using the command
blkid:- # 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 Fedora 41 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.
- Next, make a symbolic link to the unlocked root volume
- ln -s /dev/mapper/luks-$UUID /dev/root
- With the root volume available, you may continue booting the system by exiting the dracut shell
- exit
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