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   dracut    ( 8 )

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Исправление проблем (Troubleshooting)

If the boot process does not succeed, you have several options to debug the situation. Some of the basic operations are covered here. For more information you should also visit: https://www.kernel.org/pub/linux/utils/boot/dracut/dracut.html

Identifying your problem area 1. Remove 'rhgb' and 'quiet' from the kernel command line

2. Add 'rd.shell' to the kernel command line. This will present a shell should dracut be unable to locate your root device

3. 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

4. The file /run/initramfs/rdsosreport.txt is generated, which contains all the logs and the output of all significant tools, which are mentioned later.

If you want to save that output, simply mount /boot by hand or insert an USB stick and mount that. Then you can store the output for later inspection.

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. /boot/grub2/grub.cfg) or from /proc/cmdline.

• A copy of your disk partition information from /etc/fstab, which might be obtained booting an old working initramfs or a rescue medium.

• Turn on dracut debugging (see the debugging dracut section), and attach the file /run/initramfs/rdsosreport.txt.

• If you use a dracut configuration file, please include /etc/dracut.conf and all files in /etc/dracut.conf.d/*.conf

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 section called 'All bug reports', include the following information:

• Please include the output of

# /sbin/ifup <interfacename> # 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.

1. First, enable serial console output for both the kernel and the bootloader.

2. Open the file /boot/grub2/grub.cfg for editing. Below the line 'timeout=5', add the following:

serial --unit=0 --speed=9600 terminal --timeout=5 serial console

3. Also in /boot/grub2/grub.cfg, add the following boot arguments to the 'kernel' line:

console=tty0 console=ttyS0,9600

4. When finished, the /boot/grub2/grub.cfg 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

5. 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 .

6. Redirecting non-interactive output

Note 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:

1. Add the boot parameter 'rd.shell' to your bootloader configuration file (e.g. /boot/grub2/grub.cfg)

2. Remove the boot arguments 'rhgb' and 'quiet'

A sample /boot/grub2/grub.cfg 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

3. 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.

#

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

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.example: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.

1. 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

2. You recall that your root volume was a LVM logical volume. Scan and activate any logical volumes.

# lvm vgscan # lvm vgchange -ay

3. 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"

4. 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.

5. Next, make a symbolic link to the unlocked root volume

# ln -s /dev/mapper/luks-$UUID /dev/root

6. With the root volume available, you may continue booting the system by exiting the dracut shell

# exit

Additional dracut boot parameters For more debugging options, see dracut.cmdline(7).

Debugging dracut on shutdown To debug the shutdown sequence on systemd systems, you can rd.break on pre-shutdown or shutdown.

To do this from an already booted system:

# mkdir -p /run/initramfs/etc/cmdline.d # echo "rd.debug rd.break=pre-shutdown rd.break=shutdown" > /run/initramfs/etc/cmdline.d/debug.conf # touch /run/initramfs/.need_shutdown

This will give you a dracut shell after the system pivot'ed back in the initramfs.