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Creating graph of Trac workflow

Submitted by sandip on Fri, 08/15/2008 - 12:01. | Tags:
1
point

Here is how, I was able to generate graph of the workflow being used in Trac. This helps quite a bit when trying to visualize the workflow that is being setup.

The packages required were ghostscript (ps2pdf conversion) and graphviz (graph creation).

Graphviz is available in DAGs/rpmforge repository, so do an install via:

# yum --enablerepo=rpmforge install ghostscript graphviz graphviz-python

Once graphviz is installed generate config files:

# dot -c

Download the corresponding contrib files from the trac svn:

$ wget http://svn.edgewall.com/repos/trac/tags/trac-0.11/contrib/workflow/showworkflow
$ wget http://svn.edgewall.com/repos/trac/tags/trac-0.11/contrib/workflow/workflow_parser.py

Make the files executable and run:

./showworkflow /path/to/trac.ini

This should generate a pdf file in the same directory as trac.ini file.

Note: If doing this on a server xpdf will fail, so move the pdf to a web accessible directory to view it.

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Bridge Networking On OpenVZ Containers Using VETH Devices

Submitted by sandip on Wed, 08/13/2008 - 23:52. | Tags:
1
point

1. Host will be open on LAN and guests on WAN. Additionally, there is a bridged LAN for guests.
2. We will be using bridge networking for protecting the Host Network and saving IP addresses, also giving flexibility with the guest network setup.
3. Configure LAN Eth1 port to 192.168.1.2
4. WAN Eth0 port is not assigned any IP address.
6. Install the required bridge-utils package via:

yum install bridge-utils

* Network:

# cat /etc/sysconfig/network
NETWORKING=yes
NETWORKING_IPV6=no
HOSTNAME=<host.domain.tld>
GATEWAY=192.168.1.1
GATEWAYDEV="eth1"

* WAN Bridge device br0:

# cat /etc/sysconfig/network-scripts/ifcfg-br0
DEVICE=br0
BROADCAST=xxx.xxx.xxx.xxx
NETMASK=255.255.255.24
NETWORK=xxx.xxx.xxx.xxx
ONBOOT=yes
GATEWAY=xxx.xxx.xxx.xxx
TYPE=Bridge

* WAN eth0 device:

# cat /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
HWADDR=00:30:48:65:12:b4
ONBOOT=yes
TYPE=Ethernet
BRIDGE=br0

* LAN Bridge device br1:

# cat /etc/sysconfig/network-scripts/ifcfg-br1
DEVICE=br1
ONBOOT=yes
TYPE=Bridge
IPADDR=192.168.1.2
NETMASK=255.255.255.0
GATEWAY=192.168.1.1

* LAN eth1 device:

# cat /etc/sysconfig/network-scripts/ifcfg-eth1
DEVICE=eth1
HWADDR=00:30:48:65:12:b5
ONBOOT=yes
TYPE=Ethernet
BRIDGE=br1

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Difference between bytes and bits

Submitted by sandip on Sat, 07/26/2008 - 13:34. | Tags:
1
point

Bits are 1s or 0s representing the state of a switch, in binary form.

A byte is a binary word, consisting of 8 bits.

8 bits equals one Byte.

1024 bytes equals one KiloByte (KB)

1024 KiloBytes equals one MegaByte (MB)

1024 MegaBytes equals one GigaByte (GB)

Sometimes people use 1000 instead of 1024, so numbers sometimes get screwy.

A bit is always represented by a small "b", a Byte is always represented by a large "B".

It is common practice to use bits in reference to interface speeds and bytes in reference to memory and storage capacities.

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Importing existing SSL key and certificate for tomcat

Submitted by sandip on Fri, 07/25/2008 - 16:50. | Tags:
1
point
  1. Convert key and cert to a single pkcs12 format.

    openssl pkcs12 -export -inkey <pathto>/key.txt -in <pathto>/cert.txt -out cert.pkcs12

  2. Remove existing tomcat aliased PrivateKeyEntry from cacerts.

    keytool -delete -alias tomcat -keystore <pathto>/cacerts

  3. Use java-1.6 keytools to import PKCS12 keystoretype into existing cacerts keystore file.

    keytool -importkeystore -destkeystore cacerts -srckeystore cert.pkcs12 -srcstoretype PKCS12

  4. Note the alias of the newly imported PrivateKeyEntry, which would normally be 1.

    keytool -list -keystore <pathto>/cacerts | grep PrivateKeyEntry

  5. Change the alias to tomcat.

    keytool -changealias -alias 1 -destalias tomcat -keystore <pathto>/cacerts

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Simple captcha for oscommerce contact form

Submitted by sandip on Thu, 07/24/2008 - 21:52. | Tags:
1
point

Embed the captcha image by calling a php script in "contact_us.php":

<img src="/image.php" width="60" height="20" alt="Please enter the values from this image" />

Edit contact_us.php file and exactly after the below line:

  if (isset($HTTP_GET_VARS['action']) && ($HTTP_GET_VARS['action'] == 'send')) {

place the verification code:

        // Captcha check
        $t = trim($HTTP_POST_VARS['verify']);
        if ($t == "") {
                $captcha_error = "Enter the verification code!";
                $error = true;
                $messageStack->add('contact', $captcha_error);
        } else if (trim($_SESSION["thecode"]) == "") {
                $captcha_error = "No verification code generated!";
                $error = true;
                $messageStack->add('contact', $captcha_error);
        } else if ($_SESSION["thecode"] != strtoupper($t)) {
                $captcha_error = "Invalid verification code!";
                $error = true;
                $messageStack->add('contact', $captcha_error);
        }
        else
        { // End Captcha Check

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Support for 32 bit development libraries on 64 bit CentOS

Submitted by sandip on Fri, 07/18/2008 - 09:45. | Tags:
1
point

To support C/C++ 32 bit development libraries on CentOS-5.2 x86_64 arch the below devel packages are required:

yum install glibc-devel.i386 libstdc++-devel.i386

Below is example output of multilib support for gcc:

$ gcc -print-multi-lib; gcc -print-multi-os-directory; gcc -print-multi-os-directory -m32
.;
32;@m32
../lib64
../lib

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Create users in OpenVZ Containers

Submitted by sandip on Fri, 07/11/2008 - 00:35. | Tags:
1
point

Helper script to create users on all OpenVZ VEs simultaneously:

#!/bin/bash
# create_ve_users.sh
# Usage: ./create_ve_users.sh <username> <password> <uid> <group1,group2>

USERNAME=$1
PASSWORD=$2
USERID=$3
GROUP=$4
EXPECTED_ARGS=4

OUT_FILE=.create_users_$$

if [ $# -ne $EXPECTED_ARGS ]
then
  echo "Usage: `basename $0` <username> <password> <uid> <group1,group2>"
  exit 65
fi

VE_LIST=$(/usr/sbin/vzlist -H -o veid)

for VE in ${VE_LIST}
do
        vzctl exec $VE \
                "echo useradd -u $USERID -G $GROUP -p \''`openssl passwd -1 $PASSWORD`'\' $USERNAME > /tmp/${OUT_FILE} ; \
                sh /tmp/${OUT_FILE} ; \
                rm -f /tmp/${OUT_FILE}"
done

exit 0

»

Update OpenVZ containers

Submitted by sandip on Wed, 07/09/2008 - 16:51. | Tags:
1
point

If you manage several OpenVZ containers, here is a simple bash script to keep the OpenVZ containers upto date.

#!/bin/bash
# vzyum_updates.sh
# updates VEs

VE_LIST=$(/usr/sbin/vzlist -H -o veid | grep -v Warning)

for VE in ${VE_LIST}
do
  /usr/bin/vzyum $VE update
done

exit 0

»

OpenVZ CentOS template cache creation with vzpkgcache

Submitted by sandip on Mon, 07/07/2008 - 23:44. | Tags:
1
point

Following the instruction over at OpenVZ Wiki, I've had no problems with the installation and creation of templates prior to CentOS-5.2 on x86_64 systems. However, with the latest set of updates to CentOS-5.2, the vzpkgcache seems to have been broken as sysklogd is no longer being installed by default. Below is how I got it to work:

Note: edit /vz/template/centos/5/x86_64/config/minimal.list and append .x86_64 to all except for the addons packages. Then run:

# vzpkgcache -f centos-5-x86_64-minimal

which gives the below error at the end:

sed: can't read /etc/init.d/syslog: No such file or directory
ERROR: Script install-post failed

The solution was to edit "/vz/template/centos/5/x86_64/config/install-post" and set syslog and syslog.conf sed replacements with exit status of "0".

# Disable klogd
$VZCTL exec2 $VEID \
        "sed -i -e 's/daemon\\ klogd/passed\\ klogd\\ skipped/' \
                -e 's/killproc\\ klogd/passed\\ klogd\\ skipped/' \
                        /etc/init.d/syslog; exit 0"
...
# Disable fsync() in syslog
$VZCTL exec2 $VEID \
        "sed -i -e 's@\\\([[:space:]]\\\)\\\(/var/log/\\\)@\\\1-\\\2@' \
                /etc/syslog.conf; exit 0"

»

Reducing logical volume

Submitted by sandip on Thu, 07/03/2008 - 09:56. | Tags:
1
point

I've had to reduce the logical volume that was alloted for mysql data from 8GB to 4GB, which was a breeze with e2fsadm available for lvm1 on RHEL-3 .

Stop the running serivces using the volume:

# service httpd stop
# service mysqld stop

e2fsadm will reduce the filesystem and then the logical volume.

# umount /mnt/lv-mysql
# e2fsadm -L -4G /dev/hdb2-vg00/lv-mysql
# mount /mnt/lv-mysql

Check with df, which should now show the new volume size:

$ df -h /mnt/lv-mysql
Filesystem              Size  Used Avail Use% Mounted on
/dev/hdb2-vg00/lv-mysql 4.0G  531M  3.3G  14% /mnt/lv-mysql

Start the running serivces using the volume:

# service httpd start
# service mysqld start

Note: e2fsadm is not available in lvm2 and will need to reduce in two steps:

1. Reduce the filesystem residing on the logical volume.
2. Reduce the logical volume.

# resize2fs /dev/vg0/lv0 4G
# lvreduce -L -4G /dev/vg0/lv0

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