CT's Tech Notes

This article provides steps to install complete mail server environment. Install CentOS6 with minimal installation Disable selinux sed -i -e 's/enforcing/disabled/' /etc/sysconfig/selinux Import GPG keys rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY* Enable RPMforge rpm --import http://dag.wieers.com/rpm/packages/RPM-GPG-KEY.dag.txt wget http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm rpm -ivh rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm Enable EPEL rpm --import https://fedoraproject.org/static/0608B895.txt wget http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm rpm -ivh epel-release-6-8.noarch.rpm Install yum-porities (Important to overcome package conflict) yum install yum-priorities Set EPEL to priority 10 [epel] name=Extra Packages for Enterprise Linux 6 - $basearch #baseurl=http://download.fedoraproject.org/pub/epel/6/$basearch mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=e...

This note includes useful commands to adjust guest OS resources allocation at OpenVZ environment. Monitor kmemsize usages cat /proc/user_beancounters Version: 2.5 uid resource held maxheld barrier limit failcnt vm01: kmemsize 836919 1005343 2752512 2936012 0 May increase the barrier and limit vzctl set vm01 --kmemsize [barrier in number]:[limit in number] --save Validate config vzcfgvalidate /etc/vz/conf/vm01.conf Monitor Disk usage vzquota stat vm01 resource usage softlimit hardlimit grace 1k-blocks 327664 1048576 1153434 inodes 18857 200000 220000 Increase diskspace vzctl set vm01 --diskspace 20G:25G --save Increase double of inodes vzctl set vm01 --diskinodes $(( 200000*2 )):$(( 220000*2 )) --save Set CPU allocation vzctl set vm01 --cpuunits 1000 --save vzctl set vm02 --cpuunits 1000 --save vzctl set vm03 --cpuunits 200...

To encrypt a file using AES with a 256 bit key-length: openssl enc -e -aes-256-cbc -salt -in filename.odp -out filename.odp.enc To decrypt the file: openssl enc -d -aes-256-cbc -in filename.odp.enc -out filename.odp

This note provides typical setup steps for Jboss application server. Initial setup Install Java Install apache-ant (Just need to extract the zip) Configure environment variable For example /root/.bash_profile ANT_HOME=/opt/ant PATH=/opt/java/bin:$ANT_HOME/bin:$PATH:$HOME/bin:./ JAVA_HOME=/opt/java export JAVA_HOME export PATH export CLASSPATH=/usr/java/jdk/lib/tools.jar:/usr/java/jdk/jre/lib/rt.jar:./ Install jboss GA version http://sourceforge.net/projects/jboss   Unzip it at /opt directory Configure environment variable /root/.bash_profile JBOSS_HOME=/opt/jboss export JBOSS_HOME Write init script to start Startup nohup /opt/jboss/bin/run.sh -b 0.0.0.0 & Shutdown opt/jboss/bin/shutdown -S Install mod_jk for apache proxying http://www.apache.org/dist/tomcat/tomcat-connectors/jk/binaries/linux Copy mod_jk.so to /etc/httpd/modules Edit httpd.config for mod_jk vi /etc/httpd/conf/httpd.conf Include conf/mod_jk.conf Create /etc/httpd/conf/mod_jk.c...

This note provides steps for up and running haproxy loadbalancer for http service. Install haproxy rpm yum install haproxy Edit haproxy.cfg vi /etc/haproxy/haproxy.cfg global maxconn 100000 user haproxy group haproxy defaults #log global mode http # option httplog # option dontlognull retries 3 option redispatch maxconn 100000 contimeout 5000 clitimeout 50000 srvtimeout 50000 VIP address. Do not add config at /etc/sysctl.conf listen webfarm 192.168.1.3:80 It can be tcp or http mode http # stats enable # stats auth someuser:somepassword balance roundrobin # allow to track source ip option forwardfor option httpchk HEAD /linkcheck.html HTTP/1.0 server webA 192.168.1.1:80 cookie A check server webB 192.168.1.2:80 cookie B check Edit system parameter vi /etc/sysctl.conf net.ipv4.ip_nonlocal_bind = 1

Openldap is popular opensource directory service. This tutorial will setup replication feature of Openldap with two servers. At LDAP1 Edit /etc/openldap/slapd.conf suffix "o=cloudtalents.info,o=asp" rootdn "o=cloudtalents.info,o=asp" rootpw secret loglevel 4095 Replica host=sandbox2:389 suffix="o=cloudtalents.info,o=asp" binddn="o=cloudtalents.info,o=asp" bindmethod=simple credentials=secret replogfile /var/log/replogfile At LDAP2 Edit /etc/openldap/slapd.conf suffix "o=cloudtalents.info,o=asp" rootdn "o=cloudtalents.info,o=asp" rootpw secret updatedn o=cloudtalents.info,o=asp updateref ldap://sandbox1 Start ldap service and check the directory tree. ldapsearch -x -b "o=cloudtalents.info,o=asp" "(objectclass=*)" You may import the backup ldiff file ldapadd -D "o=cloudtalents.info,o=asp" -W -x -f backup...

This steps will be general procedures to edit initial ram disk Create temporary directory. For this case, i will create /boot/img mkdir /boot/img Change initrd file name mv /boot/initrd.xx.img /boot/img/initrd.xx.img.gz Unzip and extract image cd /boot/img gunzip initrd.xx.img.gz cpio -idumv < initrd.xx.img.gz You will have extracted directory. Now you can edit or add necessary drivers. This will be how to repackage Go to your extracted temporary directory. For my case, /boot/img find . | cpio -o -H newc | gzip -11 > ../initrd.xx.img