Pete's Place

The view from Hells Kitchen...no DareDevil yet....

Meanwhile, in the world I wish I lived in…

... Fortunately, the responsibility for providing evidence is on the part of the person making the claim, not the critic. It is not the responsibility of UFO skeptics to prove that a UFO has never existed, nor is it the responsibility of paranormal-health-claims skeptics to prove that crystals or colored lights never healed anyone. The skeptic's role is to point out claims that are not adequately supported by acceptable evidcence and to provide plausible alternative explanations that are more in keeping with the accepted body of scientific evidence. ... - Thomas L. Creed, The Skeptical Inquirer, Vol. XII No. 2, pg. 215

How to mount LVM partitions from rescue mode (Fedora/CentOS/RedHat)

Boot your rescue media.
Scan for volume groups:
# lvm vgscan -v
Activate all volume groups:
# lvm vgchange -a y
List logical volumes:
# lvm lvs –all
With this information, and the volumes activated, you should be able to mount the volumes:
# mount /dev/volumegroup/logicalvolume /mountpoint

How to convert RHEL5 to CentOS5

# Determine version and architecture of installed RHEL
cat /etc/redhat-release
uname -i

# Go to working directory
mkdir /root/centos5
cd /root/centos5
# Download the necessary files
wget http://mirror.umd.edu/centos/5.8/os/x86_64/CentOS/centos-release-notes-5.8-0.x86_64.rpm
wget http://mirror.umd.edu/centos/5.8/os/x86_64/CentOS/centos-release-5-8.el5.centos.x86_64.rpm
wget http://mirror.umd.edu/centos/5.8/os/x86_64/CentOS/yum-3.2.22-39.el5.centos.noarch.rpm
wget http://mirror.umd.edu/centos/5.8/os/x86_64/CentOS/yum-fastestmirror-1.1.16-21.el5.centos.noarch.rpm
wget http://mirror.umd.edu/centos/5.8/os/x86_64/CentOS/yum-utils-1.1.16-21.el5.centos.noarch.rpm
wget http://mirror.umd.edu/centos/5.8/os/x86_64/RPM-GPG-KEY-CentOS-5

# Import the rpm gpg signing key
rpm --import RPM-GPG-KEY-CentOS-5

# Remove the following packages
rpm -e --nodeps redhat-release-5Server
rpm -e yum-rhn-plugin rhn-check rhnsd rhn-setup rhn-client-tools rhncfg rhncfg-client rhncfg-actions subscription-manager

# Force install the five rpm files in the working directory
rpm -Uvh --force *.rpm

# Yum update the system
yum update

# Reboot
shutdown -r now

# To avoid confusion later
sed -i 's/Red Hat Enterprise Linux Server/CentOS Server/g' /boot/grub/grub.conf

How to convert RHEL6 to CentOS6

# Remove all the yum metadata from the system
yum clean all

# Make a working directory and go there
mkdir /root/centos
cd /root/centos/

# Check the version and architecture of RHEL
# currently installed
cat /etc/redhat-release
uname -i

# Download the following 4 RPM files and 1 RPM-GPG-KEY file
# from http://mirror.umd.edu/centos/{VER}/os/{ARCH}/
# In this example, we are converting RHEL 6.1 x86_64. We will
# use the latest available version of the following packages.

wget http://mirror.umd.edu/centos/6.2/os/x86_64/Packages/centos-release-6-2.el6.centos.7.x86_64.rpm
wget http://mirror.umd.edu/centos/6.2/os/x86_64/Packages/yum-3.2.29-22.el6.centos.noarch.rpm
wget http://mirror.umd.edu/centos/6.2/os/x86_64/Packages/yum-utils-1.1.30-10.el6.noarch.rpm
wget http://mirror.umd.edu/centos/6.2/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.30-10.el6.noarch.rpm
wget http://mirror.umd.edu/centos/6.2/os/x86_64/RPM-GPG-KEY-CentOS-6

# Import the GPG signing key
rpm --import RPM-GPG-KEY-CentOS-6

# Remove the following RPMS from the system
rpm -e --nodeps redhat-release-server
rpm -e yum-rhn-plugin rhn-check rhnsd rhn-setup rhn-setup-gnome
# If the second rpm command fails because a package is not installed,
# remove the name of that package from
# the command line and re-run the command.

# Force install all 4 RPMS in the working directory
rpm -Uvh --force *.rpm

# Do a yum upgrade. It should go to a CentOS download site and ask
# to upgrade a lot of packages
yum upgrade

# Reboot the system
shutdown -r now

List all installed perl modules from the command line

perl -MFile::Find=find -MFile::Spec::Functions -Tlw -e 'find { wanted => sub{ print canonpath $_ if /\.pm\z/ }, no_chdir => 1 }, @INC'

In the above example (which is all on one line),

File::Find and File::Spec::Functions module are used to list all installed modules.

-M option loads the module. It executes use module before executing the script

-T option enables taint checking, which instructs perl to keep track of data from the user and avoid doing anything insecure with it. Here this option is used to avoid taking the current directory name from the @INC variable and listing the available .pm files from the directory recursively.

-l option enables automatic line-ending processing in the output. Print statements will have the new line separator (\n) added at the end of each line.

-w option prints any warning messages.

-e option indicates that the following string is to be interpreted as a perl script (i.e., sequence of commands).

mount: could not find any free loop device

You can see what is being used by a loop device with losetup:

# losetup /dev/loop0

/dev/loop0: [fd06]:234921356 (/linux/isos/backtrack.iso)

It is possible to increase the number of available loop devices. Free

all loop devices, and add a line with the following to

/etc/modprobe.conf:

options loop max_loop=64

(maximum is 256)

Then, do:

rmmod loop && modprobe loop

If you get an error that the module couldn't be removed, you still have loop

devices in use.

Newer kernels (2.6.21 or 2.6.22) use a dynamic allocation of loop devices,

so you will only have to create the filesystem representation of the devices:

for ((i=8;i<64;i++)); do

[ -e /dev/loop$i ] || mknod -m 0600 /dev/loop$i b 7 $i

done

Happy Pi Day!

And don’t forget 6:28pm (Tau Time)!

Future Holidays to look forward to:

March 14, 2015 = Pi Day (to 4 decimal places)
April 4, 2016 = Square Root Day
6:02am on October 23, 2012 = Mole Day (6:02 10/23)

Swap Your Laptop for an iPad + Linode

Here's an excellent Linux Journal Article which talks about using an iPad with a Bluetooth keyboard, to ssh into a Linux host:

Linux Journal Article: http://www.linuxjournal.com/content/swap-your-laptop-ipad-linode?page=0,0

The Linux host is a virtualized node in "the cloud":

Linode: http://www.linode.com/

And the SSH client for iPad can be found here:

iSSH for iPad app: http://itunes.apple.com/us/app/issh-ssh-vnc-console/id287765826?mt=8

I've tried this app on my iPad and I think this works a lot better than I thought it would!

IT Certification Master

I found a new site with lots of IT Certification infomation. It's new, but it looks like a really good start. Check it out here: http://www.itcertificationmaster.com/

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