{"id":1604,"date":"2013-10-23T23:52:55","date_gmt":"2013-10-23T21:52:55","guid":{"rendered":"http:\/\/www.extradrm.com\/?p=1604"},"modified":"2013-10-28T00:46:44","modified_gmt":"2013-10-27T22:46:44","slug":"centos-useful-commands","status":"publish","type":"post","link":"https:\/\/www.extradrm.com\/?p=1604","title":{"rendered":"Centos useful commands"},"content":{"rendered":"

Now a days While working on latest version of CentOS , i get to know some important but initial commands,which are most frequently used or commonly used CentOS .<\/p>\n

Common used phrase \u201cyum<\/strong>\u201d means: Yellowdog Updater Modified.
\nSearch for any Installed Packages [ Syntax]:<\/strong><\/p>\n

#yum list<\/pre>\n
List of updated software (security fix) [ Syntax]:<\/strong><\/p>\n
#yum list updates<\/pre>\n
Example: for check installed mysql version:<\/strong><\/p>\n
#mysql -v<\/pre>\n
Switch User [ Syntax]:<\/strong><\/p>\n
#su \u2013<\/pre>\n
is to connect as root<\/p>\n
#su oracle<\/pre>\n
Anyway, If no username is specified, then the root user is assumed.<\/p>\n
Get Full package info of Installed Package [Syntax]:<\/strong><\/p>\n
#yum info<\/pre>\n
Example:<\/p>\n
#yum info php<\/pre>\n
Example: yum info php \u2013 Will show Full version info for php package.<\/p>\n
Grep command [Syntax]:<\/strong><\/p>\n
#grep<\/pre>\n
Grep With custom Switch:<\/p>\n
# rpm -qa | grep php<\/pre>\n
Pipe | used for transfer output of rpm command to grep command.
\nRPM (Redhat Package Manager): RPM installs already configured and compiled software in your system.<\/p>\n
Search Any Package on Mirrors \/ Repository [ Syntax]:<\/strong><\/p>\n
#yum search<\/pre>\n
Example – Search All bcmath Package available on Mirrors \/ Repository :<\/p>\n
#yum search bcmath<\/pre>\n
Install Any Package [ Syntax]:<\/strong><\/p>\n
#yum install<\/pre>\n
Example \u2013 Will install php-bcmath package\/module :<\/p>\n
#yum install php-bcmath<\/pre>\n
Remove package [Syntax]:<\/strong><\/p>\n
# yum remove<\/pre>\n
Example \u2013 Will remove mysql package :<\/p>\n
#yum remove mysql<\/pre>\n
\n
Checking disk usage (lsblk or df or fdisk)<\/h2>\n
Command: lsblk<\/h3>\n
The \u201clsblk<\/strong>\u201d stands for (List Block Devices<\/strong>), print block devices by their assigned name on the standard output in a tree-like fashion.<\/p>\n
root@centos:~# lsblk\r\n\r\nNAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT\r\nsda      8:0    0 232.9G  0 disk \r\n\u251c\u2500sda1   8:1    0  46.6G  0 part \/\r\n\u251c\u2500sda2   8:2    0     1K  0 part \r\n\u251c\u2500sda5   8:5    0   190M  0 part \/boot\r\n\u251c\u2500sda6   8:6    0   3.7G  0 part [SWAP]\r\n\u251c\u2500sda7   8:7    0  93.1G  0 part \/data\r\n\u2514\u2500sda8   8:8    0  89.2G  0 part \/personal\r\nsr0     11:0    1  1024M  0 rom<\/pre>\n
The \u201clsblk -l<\/strong>\u201d command list block devices in \u2018list<\/strong>\u2018 structure (not tree like fashion).<\/p>\n
root@centos:~# lsblk -l\r\n\r\nNAME MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT\r\nsda    8:0    0 232.9G  0 disk \r\nsda1   8:1    0  46.6G  0 part \/\r\nsda2   8:2    0     1K  0 part \r\nsda5   8:5    0   190M  0 part \/boot\r\nsda6   8:6    0   3.7G  0 part [SWAP]\r\nsda7   8:7    0  93.1G  0 part \/data\r\nsda8   8:8    0  89.2G  0 part \/personal\r\nsr0   11:0    1  1024M  0 rom<\/pre>\n
However, even if lsblk<\/em> is more visual, I still prefer to use df -h<\/em><\/strong>. The latter gives you more information about the remaining space, the size of the partitions, and the percentage of memory in use.<\/p>\n
\"centos-04\"<\/a><\/p>\n
\n
Services Enabling Levels<\/h2>\n
To display the current settings for a selected service only, use chkconfig --list<\/code> followed by the name of the service:<\/p>\n
chkconfig --list service_name<\/pre>\n
For example, to display the current settings for the sshd<\/code> service, type:<\/div>\n
~]#chkconfig --list sshd\r\nsshd            0:off   1:off   2:on    3:on    4:on    5:on    6:off<\/pre>\n
You can also use this command to display the status of a service that is managed by xinetd<\/strong>. In that case, the output will only contain the information whether the service is enabled or disabled:<\/p>\n
~]#chkconfig --list rsync\r\nrsync           off<\/pre>\n
Enabling a Service<\/h4>\n
To enable a service in runlevels 2, 3, 4, and 5, type the following at a shell prompt as root :<\/p>\n
chkconfig service_name on<\/pre>\n
For example, to enable the httpd\/Apache service in these four runlevels, type:<\/p>\n
~]#chkconfig httpd on<\/pre>\n
\n
Listing running modules<\/h2>\n
But first you need to know which modules are currently running. The command for that is<\/p>\n
lsmod<\/pre>\n
\"centos-05\"<\/a><\/p>\n
whereis<\/em> <\/strong>can locate binaries, manual entries, and various configuration files. Its syntax is also very simple:<\/p>\n
whereis [name]<\/pre>\n
\"centos-06\"<\/a><\/p>\n
In the example above, I asked where Firefox was, and the command returned the location for its binary and various directories, as well as the manual page.<\/p>\n
But one of the greatest strengths of whereis<\/em> is its ability to locate standalone configuration files. Here is another example, where I was searching for rc<\/em> configuration files:<\/p>\n
\"centos-07\"<\/a><\/p>\n
Create a User and directories for Oracle<\/h3>\n
Create two groups, oinstall and dba<\/p>\n
groupadd oinstall\r\ngroupadd dba<\/pre>\n
Create user oracle, and assign him to the groups and give him a password.<\/p>\n
useradd -g oinstall -G dba -p password -d \/home\/oracle -s \/bin\/bash oracle\r\npasswd oracle<\/pre>\n
Directories<\/h3>\n
Create the following directories and assign them to user and dba group for oracle install<\/p>\n
mkdir -p \/u01\/app\/oracle\r\nmkdir -p \/u02\/app\/oracle\r\nmkdir -p \/u03\/app\/oracle\r\nchown -R oracle:dba \/u01\r\nchown -R oracle:dba \/u02\r\nchown -R oracle:dba \/u03<\/pre>\n
\n
Install lamp server on centos<\/h3>\n
LAMP is an acronym for a solution stack of free, open source software, originally coined from the first letters of L<\/b>inux (operating system), A<\/b>pache HTTP Server, M<\/b>ySQL (database software), and P<\/b>HP, principal components to build a viable general purpose web server.<\/p>\n
Install Apache. (httpd or apache2)<\/b><\/p>\n
#\u00a0yum -y install httpd<\/i><\/pre>\n
Adding Apache to startup, so it can automatic loaded if system restarted.<\/p>\n
#\u00a0chkconfig --levels 235 httpd on<\/i><\/pre>\n
# service httpd start<\/i><\/pre>\n
To check Apache has installed on server go to http:\/\/YourIPAddress\/<\/b><\/i> and if you see as in the screenshoot that means Apache has been installed on your server.<\/p>\n
To stop Firewall services you can follow the commands below :\"centos-10\"<\/a><\/p>\n
if you want to keep firewall on and If you get message “No Route To Host<\/i>” that means you must open port 80 that still closed by firewall.
\nTo open port 80 simply do this step:<\/p>\n
# vi \/etc\/sysconfig\/iptables<\/i><\/pre>\n
Add this command and save (to save press key “Esc” and then type “:wq”)<\/p>\n
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 80 -j ACCEPT<\/pre>\n
-A INPUT -m state --state NEW -m tcp -p tcp --dport 443 -j ACCEPT<\/pre>\n
And then restart IPTABLES<\/p>\n
# service iptables restart<\/i><\/pre>\n
Install MySQL<\/b><\/p>\n
# yum install mysql mysql-server<\/i><\/pre>\n
Adding MySQL to startup<\/p>\n
# chkconfig --levels 235 mysqld on<\/i>\r\n# \/etc\/init.d\/mysqld start<\/i><\/pre>\n
Create MySQLadmin User and Password or use mysql_secure admin<\/span> utility as below in screenshot<\/strong><\/p>\n
# mysqladmin -u root password YourPassSQL<\/i><\/pre>\n
# mysqladmin -h HostNameServer -u root password Y<\/i>ourPassSQL<\/i><\/pre>\n
\"centos-11\"<\/a><\/p>\n
Install PHP <\/b><\/p>\n
# yum install php php-mysql php-mbstring php-gd php-imap php-ldap php-odbc php-pear php-xml php-xmlrpc<\/i><\/pre>\n
Restart Apache<\/p>\n
# service httpd restart<\/i><\/pre>\n
To check php has been installed on server simply do following step:<\/p>\n
# vi \/var\/www\/http\/php\/index.php<\/i><\/pre>\n
and type following php code:<\/p>\n
<?php\r\nphpinfo();\r\n?><\/i><\/pre>\n
Save and go to http:\/\/YourIPAddress\/php\u00a0 <\/b><\/i>
\nif php has been installed on your server, you will see php version and modules installed.<\/p>\n
Install phpmyadmin on centos 5.5
\n<\/strong><\/p>\n
You will need to install and Enable EPEL Repository<\/a> :<\/p>\n
## RHEL\/CentOS 5 32 Bit OS ##<\/strong>\r\n# wget http:\/\/packages.sw.be\/rpmforge-release\/rpmforge-release-0.5.2-2.el5.rf.i386.rpm\r\n# rpm -Uvh rpmforge-release-0.5.2-2.el5.rf.i386.rpm<\/pre>\n
Next, you\u2019ll need to download and install DAG\u2019s GPG<\/strong> key for your system.<\/p>\n
# wget http:\/\/dag.wieers.com\/rpm\/packages\/RPM-GPG-KEY.dag.txt\r\n# rpm --import RPM-GPG-KEY.dag.txt<\/pre>\n
yum --enablerepo=rpmforge install phpmyadmin<\/pre>\n
When installation is done, you can edit \/etc\/httpd\/conf.d\/phpmyadmin.conf and allow it to be opened from anywhere and not just the same computer. You are going to need this if you have installed it in a remote virtual server.
\nTo do so, open up \/etc\/httpd\/conf.d\/phpmyadmin.conf using:<\/p>\n
nano \/etc\/httpd\/conf.d\/phpmyadmin.conf<\/pre>\n
You will see:<\/p>\n
<Directory \u201c\/usr\/share\/phpmyadmin\u201d><\/strong>
\n Order Deny,Allow<\/strong>
\n Allow from all<\/strong>
\n Allow from 127.0.0.1<\/strong>
\n <\/Directory><\/strong><\/p>\n
Now, you can access phpMyAdmin by visiting http:\/\/vps_server_IP_or_domain\/phpmyadmin. But you will get the following error:<\/p>\n
Error
\nThe configuration file now needs a secret passphrase (blowfish_secret).<\/p>\n
nano \/usr\/share\/phpmyadmin\/config.inc.php<\/pre>\n
Find a line saying:<\/p>\n
$cfg['blowfish_secret'] = ''; \/* YOU MUST FILL IN THIS\r\nFOR\r\nCOOKIE AUTH! *\/<\/pre>\n
Fill in any secret keyword there, eg mysecretpassphrase, so that it looks like:<\/p>\n
$cfg['blowfish_secret'] = 'mysecretpassphrase'; \/* YOU MUST FILL IN THIS\r\nFOR\r\nCOOKIE AUTH! *\/<\/pre>\n
and then save it.<\/p>\n
Now, you must restart apache. To do so, run<\/p>\n
service httpd restart<\/pre>\n
Now, you can access phpMyAdmin by visiting http:\/\/vps_server_IP_or_domain\/phpmyadmin<\/p>\n
Will be continued ….<\/p>\n
 <\/p>\n","protected":false},"excerpt":{"rendered":"
Now a days While working on latest version of CentOS , i get to know some important but initial commands,which are most frequently used or commonly used CentOS . Common used phrase \u201cyum\u201d means:...<\/p>\n","protected":false},"author":1,"featured_media":2843,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[241,14],"tags":[],"youtube_video":null,"_links":{"self":[{"href":"https:\/\/www.extradrm.com\/index.php?rest_route=\/wp\/v2\/posts\/1604"}],"collection":[{"href":"https:\/\/www.extradrm.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.extradrm.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.extradrm.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.extradrm.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1604"}],"version-history":[{"count":0,"href":"https:\/\/www.extradrm.com\/index.php?rest_route=\/wp\/v2\/posts\/1604\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.extradrm.com\/index.php?rest_route=\/wp\/v2\/media\/2843"}],"wp:attachment":[{"href":"https:\/\/www.extradrm.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1604"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.extradrm.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1604"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.extradrm.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1604"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}