Latest revision as of 18:47, 26 March 2017

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 rd.shell to the kernel command line. This will present a shell should dracut be unable to locate your root device
Add rd.shell rd.debug log_buf_len=1M to the kernel command line so that dracut shell commands are printed as they are executed

Inspect the system logs:

 # less /run/initramfs/rdsosreport.txt
 # journalctl -a
 # dmesg
 # less /run/initramfs/init.log

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

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 /etc/grub.conf for 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.conf 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 [1].

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

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 rd.shell 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 rd.shell 
        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
```

Summary of dracut kernel command line options

A selection of the most common debugging related dracut options:

rd.shell: Drop to a shell, if the initramfs fails.
rd.debug: set -x for the dracut shell.
rd.break=[cmdline|pre-udev|pre-trigger|initqueue|pre-mount|mount|pre-pivot|cleanup]: drop the shell on defined breakpoint (use egrep 'rd.?break' /usr/lib/dracut/modules.d/99base/init.sh to find the breakpoints supported by your dracut version)
rd.udev.info: set udev to loglevel info
rd.udev.debug: set udev to loglevel debug

See the dracut.cmdline(7) man page for the complete reference.

@@ Line 9: / Line 9: @@
 = Identifying your problem area =
-{{admon/note|FIXME|provide guidance on what dracut bugs look like.  How to tell if this is related to dracut, or just a kernel problem?}}
+<ol>
+<li> Remove <code>rhgb</code> and <code>quiet</code> from the kernel command line
+<li> Add <code>rd.shell</code> to the kernel command line.  This will present a shell should dracut be unable to locate your root device
+<li> Add <code>rd.shell rd.debug log_buf_len=1M</code> to the kernel command line so that dracut shell commands are printed as they are executed
+<li> Inspect the system logs:
+<pre>
+ # less /run/initramfs/rdsosreport.txt
+ # journalctl -a
+ # dmesg
+ # less /run/initramfs/init.log
+</pre>
+</ol>
 = Information to include in your report =
@@ Line 52: / Line 63: @@
 == 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 capture boot messages.
+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.
+  <ol>
+    <li> Open the file {{filename|/etc/grub.conf}} for editing.  Below the line ''timeout=5'', add the following:
+    <pre>serial --unit=0 --speed=9600
+terminal --timeout=5 serial console</pre>
+    <li> Also in {{filename|/etc/grub.conf}}, add the following boot arguemnts to the ''kernel'' line:
+    <pre>console=tty0 console=ttyS0,9600</pre>
+    <li> When finished, the {{filename|/etc/grub.conf}} file should look similar to the example below.
+    <pre>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</pre>
+</ol>
-# First, enable serial console output for both the kernel and the bootloader.
+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].
-#* Open the file {{filename|/etc/grub.conf}} for editing.  Below the line ''timeout=5'', add the following:
-#*: <pre>serial --unit=0 --speed=9600
-#*: terminal --timeout=5 serial console</pre>
-#* Also in {{filename|/etc/grub.conf}}, add the following boot arguemnts to the ''kernel'' line:
-#*: <pre>console=tty0 console=ttyS0,9600</pre>
-#* When finished, the {{filename|/etc/grub.conf}} file should look similar to the example below.
-#*:<pre>
-#*: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</pre>
-#* 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].
 {{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
 <pre>exec >/dev/kmsg 2>&1 </dev/console</pre>}}
-== Enable the dracut debug module ==
+== Using the dracut shell ==
-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.
-# Create a dracut ramdisk image with debugging enabled
-#: <pre>dracut -a debug /boot/initrd-debug-$(uname -r).img $(uname -r) </pre>
-# Next, tell your bootloader to use the new dracut ramdisk
-#: <pre>grubby --make-default --title "Debugging dracut" \
-#:  --add-kernel /boot/vmlinuz-$(uname -r) \
-#:  --initrd /boot/initrd-debug-$(uname -r).img \
-#:  --copy-default</pre>
-# When ready to debug dracut, reboot the system
-== Using the 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. {{filename|/etc/grub.conf}}
+# Add the boot parameter <code>rd.shell</code> to your bootloader configuration file (e.g. {{filename|/etc/grub.conf}}
-# Remove the boot arguments ''rhgb'' and ''quiet''
+# Remove the boot arguments <code>rhgb</code> and <code>quiet</code>
 A sample {{filename|/etc/grub.conf}} bootloader configuration file is listed below.
@@ Line 102: / Line 100: @@
 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 rdshell
+         kernel /vmlinuz-2.6.29.5-191.fc11.x86_64 ro root=/dev/mapper/vg_uc1-lv_root console=tty0 rd.shell
          initrd /dracut-2.6.29.5-191.fc11.x86_64.img</pre>
-{{admon/note|FIXME|Need sample shell commands.}}
+If system boot fails, you will be dropped into a shell as seen in the example below.
+<pre>
-== Additional dracut boot parameters ==
+No root device found
+Dropping to debug shell.
-<pre>rdshell</pre>
-{{admon/note|Drop to a shell, if the initramfs fails.}}
-<pre>rdinitdebug</pre>
-{{admon/note|set -x for the dracut shell}}
+sh: can't access tty; job control turned off
+#
+</pre>
-<pre>rdbreak=[pre-udev|pre-mount|mount|pre-pivot|]</pre>
+Use this shell prompt to gather the information requested above (see [[How_to_debug_Dracut_problems#AllInfo|the 'all bug reports' section]]).
-{{admon/note|drop the shell on defined breakpoint}}
+== Accessing the root volume from the dracut shell ==
-<pre>rdudevinfo</pre>
+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. {{filename|/dev/sda7}})
+* A LVM logical volume (e.g. {{filename|/dev/VolGroup00/LogVol00}})
+* An encrypted device (e.g. {{filename|/dev/mapper/luks-4d5972ea-901c-4584-bd75-1da802417d83}})
+* A network attached device (e.g. {{filename|netroot{{=}}iscsi:@192.168.0.4::3260::iqn.2009-02.org.fedoraproject:for.all}})
-{{admon/note|set udev to loglevel info}}
+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 {{filename|/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.
-<pre>rdudevdebug</pre>
+<ol>
+  <li> Inspect your partitions using {{command|parted}}
+  <pre># parted /dev/sda -s p
+Model: ATA HTS541060G9AT00 (scsi)
+Disk /dev/sda: 60.0GB
+Sector size (logical/physical): 512B/512B
+Partition Table: msdos
-{{admon/note|set udev to loglevel debug}}
+Number  Start   End     Size    Type      File system  Flags
+      32.3kB  10.8GB  107MB   primary   ext4         boot
+      10.8GB  55.6GB  44.7GB  logical                lvm</pre>
+  <li> You recall that your root volume was a LVM logical volume.  Scan and activate any logical volumes
+  <pre># lvm vgscan
+# lvm vgchange -ay</pre>
+  <li> You should see any logical volumes now using the command {{command|blkid}}:
+   <pre># 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" </pre>
+  <li> From the output above, you recall that your root volume exists on an encrypted block device.  Following the guidance disk encryption guidance from the [http://docs.fedoraproject.org/install-guide/f{{FedoraVersion}}/en-US/html/apcs04s04.html {{FedoraVersion|long}} Installation Guide], you unlock your encrypted root volume.
+  <pre>UUID=$(cryptsetup luksUUID /dev/mapper/linux-root)
+cryptsetup luksOpen /dev/mapper/linux-root luks-$UUID
+Enter passphrase for /dev/mapper/linux-root:
+Key slot 0 unlocked. </pre>
+  <li> Next, make a symbolic link to the unlocked root volume
+  <pre>ln -s /dev/mapper/luks-$UUID /dev/root</pre>
+  <li> With the root volume available, you may continue booting the system by exiting the dracut shell
+  <pre>exit</pre>
+</ol>
-<pre>rdnetdebug</pre>
+== Summary of dracut kernel command line options ==
-{{admon/note|debug network scripts in dracut. Output is written to /tmp/}}
+A selection of the most common debugging related dracut options:
-= Creating a dracut.conf =
+; rd.shell : Drop to a shell, if the initramfs fails.
+; rd.debug : set -x for the dracut shell.
+; rd.break=[cmdline|pre-udev|pre-trigger|initqueue|pre-mount|mount|pre-pivot|cleanup] : drop the shell on defined breakpoint (use <code>egrep 'rd.?break' /usr/lib/dracut/modules.d/99base/init.sh</code> to find the breakpoints supported by your dracut version)
+; rd.udev.info : set udev to loglevel info
+; rd.udev.debug : set udev to loglevel debug
-{{admon/note|FIXME|more information on creating a a dracut.conf and when that might be needed}}
+See the <code>dracut.cmdline(7)</code> [http://man7.org/linux/man-pages/man7/dracut.cmdline.7.html man page] for the complete reference.
-[[Category:Debugging]] [[Category:How to]]
+[[Category:Debugging|D]] [[Category:How to]]

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