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vzdump LVM snapshots kernel errors

Submitted by sandip on Tue, 03/31/2009 - 09:49.

On running daily lvm snapshot backups via vzdump on OpenVZ servers, I noticed the below Kernel errors in logwatch reports.


WARNING:  Kernel Errors Present
    Buffer I/O error on device dm-4,  ...:  22 Time(s)
    EXT3-fs error (device dm-4): e ...:  60 Time(s)
    lost page write due to I/O error on dm-4 ...:  22 Time(s)

This would show up on busy servers only, probably caused due to lvm snapshot running out of space.

I edited "/usr/bin/vzdump" and increased the size from 500m to 1000m which seems to have resolved the issue for now.


run_command (\*LOG, "$lvcreate --size 1000m --snapshot --name vzsnap /dev/$lvmvg/$lvmlv");

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set_loginuid failed opening loginuid

Submitted by sandip on Tue, 02/03/2009 - 10:51.

If this file doesn't exist:

/proc/<pid of crond>/loginuid

It's because the kernel doesn't have AUDIT enabled. So you get a bunch of errors in "/var/log/secure" with "set_loginuid failed opening loginuid".

Recompile kernel with audit support:

CONFIG_AUDIT=y
CONFIG_AUDITSYSCALL=y

If recompiling of kernel is not an option then:

Comment the below lines from all pam.d files.

session required        pam_loginuid.so

Find files via:

# grep -l pam_loginuid.so /etc/pam.d/*
/etc/pam.d/atd
/etc/pam.d/crond
/etc/pam.d/login
/etc/pam.d/remote
/etc/pam.d/sshd

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Automatically reboot server after a kernel panic

Submitted by wizap on Tue, 03/25/2008 - 09:12.

Add panic=10 to the kernel command line to reboot with 10 seconds of a kernel error. Be careful with this when setting up new kernels.

It’s possible to change it later with sysctl, or by writing to /proc:

# echo 10 > /proc/sys/kernel/panic

To make it permanent, edit /etc/sysctl.conf and add the below line:

kernel.panic = 10

`sysctl -p` to load the conf file and make permanent.

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Anatomy of Linux Kernel

Submitted by sandip on Sun, 11/18/2007 - 10:53.

Immensely useful article for learning about Linux kernel at IBM DeveloperWorks.

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`yum update kernel` without removing old kernels

Submitted by sandip on Mon, 06/18/2007 - 13:22.

Edit "/etc/yum/pluginconf.d/installonlyn.conf" and change the enabled to "0" or increase the "tokeep" value to the number of versions you want to keep.

[main]
enabled=1
# this sets the number of package versions which are kept
tokeep=2

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Mount and read from NTFS partitions on Linux -- Fedora Core 5

Submitted by sandip on Wed, 06/14/2006 - 22:24.
  1. Download the specific kernel module rpm from linux-ntfs.org .
  2. You can check the currently installed kernel version using `uname -rm` .
  3. Install via:
    # rpm -ivh kernel-module-ntfs-*.rpm
  4. Check the partitions to be mounted:

    # fdisk -l | grep NTFS

    Note: If using a dual boot, then windows is normally installed in the first partition, "/dev/hda1".

  5. The listed NTFS partition can be mountable after a restart via:
    # mount -r -o umask=0222 -t ntfs /dev/hda1 /mnt/ntfs
  6. For automated mounts during startup, add the below line in "/etc/fstab" .

    /dev/hda1   /mnt/ntfs     ntfs    ro,defaults,umask=0222 0 0
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