What I See

Setting up NGINX for HTTP load balancing. Nginx server is running as below. nginx-server : nginx.server.com  //nginx Below are the 3 server which run a web application which needs to be load balanced. Server1 : node1.application.com  //web_server Server2 : node2.application.com  //web_server Server3 : node3.application.com  //web_server Install NGINX on RHEL/Centos6 Step 1 : Create a Repo. in [ vim /etc/yum.repos.d/nginx.repo ] CENTOS6 [nginx] name=nginx repo baseurl= http://nginx.org/packages/centos/$releasever/$basearch/ gpgcheck=0 enabled=1 RHEL: [nginx] name=nginx repo baseurl= http://nginx.org/packages/rhel/$releasever/$basearch/ gpgcheck=0 enabled=1 Step 2 : Installation  [ahmed@ngnix ~]$ sudo yum install nginx Step 3 : Configuration:  sudo vim /etc/nginx/nginx.conf #------BEGIN CONFIG------------ user  nginx; worker_processes  1; error_log  /var/log/nginx/error.l...

Add this below tag to hbase-site.xml in all the Master and Region Server. <!-- Addding Authorization -->   <property>     <name>hbase.security.authorization</name>     <value>true</value>   </property>   <property>     <name>hbase.coprocessor.master.classes</name>     <value>org.apache.hadoop.hbase.security.access.AccessController</value>   </property>   <property>     <name>hbase.coprocessor.region.classes</name>     <value>org.apache.hadoop.hbase.security.token.TokenProvider,org.apache.hadoop.hbase.security.access.AccessController</value>   </property>   <property>     <name>hbase.rpc.engine</name>     <value>org.apache.hadoop.hbase.ipc.SecureRpcEngine</value>   </property> <!--End Authorization --> [ahmed@master home]# sudo -u hbase hbase shell hbase(main):002:0> grant ERROR: wrong number of arguments (0 for 2) Here is some h...

Check where we have DVD/CD mount points. [ahmed@zabbixmin ~]$ ll /dev | grep sr0 lrwxrwxrwx 1 root  root           3 Dec 26 16:46 cdrom -> sr0 lrwxrwxrwx 1 root  root           3 Dec 26 16:46 cdrw -> sr0 lrwxrwxrwx 1 root  root           3 Dec 26 16:46 dvd -> sr0 lrwxrwxrwx 1 root  root           3 Dec 26 16:46 dvdrw -> sr0 lrwxrwxrwx 1 root  root           3 Dec 26 16:46 scd0 -> sr0 brw-rw---- 1 root  cdrom    11,   0 Dec 26 16:46 sr0 Mount using auto select mode, from /dev/sr0 to /media/ -r : Mount the file system read-only. A synonym is -o ro. -t : Type [ahmed@zabbixmin ~]$ sudo mount -r -t auto /dev/sr0 /media/ [ahmed@zabbixmin ~]$ cd /media/ [ahmed@zabbixmin media]$ ls manifest.txt     VMwareTools-9.6.1-1378637.tar.gz  vmware-tools-upgrader-64 run_upgrader.sh  vmware-tools-upgrader-32 [ahmed@zabbixmin media]$ More Details : http://linux.about.com/od/commands/l/blcmdl8_mount.htm

Install the package including " downloadonly " plugin: (RHEL5/CentOS5) # yum install yum-downloadonly (RHEL6/CentOS6) # yum install yum-plugin-downloadonly Run yum command with " --downloadonly " option as follows: # yum install --downloadonly --downloaddir=<directory> <package> Confirm the RPM files are available in the specified download directory. Before using the plugin, check /etc/yum/pluginconf.d/downloadonly.conf to confirm that this plugin is " enabled=1 "

Adding Repos and Install Server Configuration . [ahmed@server ~]# rpm -ivh http://repo.zabbix.com/zabbix/2.4/rhel/6/x86_64/zabbix-release-2.4-1.el6.noarch.rpm [ahmed@server ~]# yum install mysql-server mysql [ahmed@server ~]# yum install zabbix-server-mysql zabbix-web-mysql [ahmed@server ~]# yum install zabbix-agent Create Database. [ahmed@server ~]# mysql -uroot mysql> create database zabbix character set utf8 collate utf8_bin; mysql> grant all privileges on zabbix.* to zabbix@localhost identified by 'zabbix'; mysql> exit Creating Schema. [ahmed@server ~]# cd /usr/share/doc/zabbix-server-mysql-2.4.0/create [ahmed@server ~]# mysql -uroot zabbix < schema.sql [ahmed@server ~]# mysql -uroot zabbix < images.sql [ahmed@server ~]# mysql -uroot zabbix < data.sql Setting Configuration. [ahmed@server ~]# vi /etc/zabbix/zabbix_server.conf DBHost=localhost DBName=zabbix DBUser=zabbix DBPassword=zabbix Start Server. [ahmed@server ~]# service zabbix-server start Apache Con...

1. List All Services, Using ' –list ' parameter will displayed all services and their current status in each run-level configuration. [ahmed@server ~]# chkconfig --list myservermgesrv  0:off   1:off   2:on    3:on    4:on    5:on    6:off abc-servc       0:off   1:off   2:off   3:on    4:off   5:on    6:off xyz:ahmed       0:off   1:off   2:off   3:on    4:off   5:on    6:off ... 2. Adding mysqld, zabbix-server, zabbix-agent, httpd to chkconfig [ahmed@server ~]# chkconfig --level 235 mysqld on [ahmed@server ~]# chkconfig --level 235 zabbix-server on [ahmed@server ~]# chkconfig --level 235 zabbix-agent on [ahmed@server ~]# chkconfig --level 235 httpd on 3. To Disable any run-level use the off parameter. [ahmed@server ~]# chkconfig --level 2 mysqld off

SELinux is a security extension of CentOS that should provide extended security.  Edit /etc/selinux/config and set SELINUX=disabled vim /etc/selinux/config # This file controls the state of SELinux on the system. # SELINUX= can take one of these three values: #     enforcing - SELinux security policy is enforced. #     permissive - SELinux prints warnings instead of enforcing. #     disabled - No SELinux policy is loaded. SELINUX= disabled # SELINUXTYPE= can take one of these two values: #     targeted - Targeted processes are protected, #     mls - Multi Level Security protection. SELINUXTYPE=targeted Afterwards we must reboot the system: [ahmed@server ~]# reboot

Creating Local Repository on server. mkdir -p /server/rpms Copy 'rpms' which are downloaded and move to /server/rpms  cp -rf from_rpms /server/rpms createrepo /server/rpms This will create all the necessary xml files in the directory. Next create a file called ' local_repos.repo '  sudo vim /etc/yum/yum.repos.d/local_repos.repo Add the below lines. [LOCAL_REPO] name=LOCAL_REPO baseurl=file:///server/rpms gpgcheck=0  enabled=1  Save the file in /etc/yum/yum.repos.d/ 

Adding access permission to port 80 $ sudo iptables -A INPUT -p tcp -m tcp --dport 80 -j ACCEPT  $ sudo iptables -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT  To save this to iptables. $ sudo /etc/init.d/iptables save

I finished installing CentOS 6.5, but when I tried running yum update I got: [zabbixmin@zabbix ~]# yum update Loaded plugins: fastestmirror, refresh-packagekit Determining fastest mirrors Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=6&arch=i386&repo=os error was 14: PYCURL ERROR 6 - "" Error: Cannot find a valid baseurl for repo: base How can I fix it? Solution : Just execute  dhclient  in the terminal, this will initialize your network interface and you should be up and running. ​

Saving Packages when doing a yum installation. These packages can be used again on a different server without having to download them again. sudo vim /etc/yum.conf  [main] cachedir=/var/cache/yum/$basearch/$releasever  keepcache=0  debuglevel=2  logfile=/var/log/yum.log  … #some more details here …  # PUT YOUR REPOS HERE OR IN separate files named file.repo  # in /etc/yum.repos.d  Change the line ` keepcache=0 ` to ` keepcache=1 ` This cache all the data in ' cachedir ' location. Some test here. [zabbix@localhost yum]$ sudo yum install yum-plugin-downloadonly ... [zabbix@localhost yum]$ pwd /var/cache/yum [zabbix@localhost yum]$ find . -name '*.rpm' -print | grep yum ./x86_64/6/base/packages/yum-utils-1.1.30-30.el6.noarch.rpm ./x86_64/6/base/packages/yum-plugin-downloadonly-1.1.30-30.el6.noarch.rpm ./x86_64/6/base/packages/yum-3.2.29-60.el6.centos.noarch.rpm [zabbix@localhost yum]$

Below is the command to find and replace a string in current directory. grep -rl '<string_to_find>' ./ | xargs sed -i 's/<string_to_find>/<new_string>/g' Here is a command which will replace all occurance of 'ahmed' with 'aariz' grep -rl 'ahmed' ./ | xargs sed -i 's/ahmed/aariz/g' More Information here : http://vasir.net/blog/ubuntu/replace_string_in_multiple_files ​

Had to import a Large File into Mysql today. Here is how you do it. :) Step 1 : Login mysql -u root -p database_name Step 2 : Set network buffer length to a large byte number set global net_buffer_length=1000000; Step 3 : Set maximum allowed packet size to a large byte number set global max_allowed_packet=1000000000; Step 4: Disable foreign key checking to avoid delays,errors and unwanted behaviour set foreign_key_checks = 0; Step 5 : Import Dump source My_Large_Dump_File.sql Step 6: Remember to enable foreign key checks when procedure is complete SET foreign_key_checks = 1; More Details on Importing Large Dump is here. https://cmanios.wordpress.com/2013/03/19/import-a-large-sql-dump-file-to-a-mysql-database-from-command-line/ ​