UUID (Universally Unique IDentifier) should be unique and it is used to identify storage devices on a linux system.
If you cloned a virtual machine from vCenter, the metadata containing information of UUID for the filesystem will be identical for the original and cloned copy, therefore the UUID is no longer unique in /etc/fstab.
If you plan to run high traffic wordpress blog(wordpress nginx), i would suggest to run it in virtual private server (VPS) or dedicated server together with NGINX FastCGI Caching.
Besides the low memory consumption when using Nginx as a web server, it has a fast performance. When you combine Nginx and FastCGI Caching module, you will further enhance the performance of your web application, including a WordPress site.
7. At the initial start up of the MySQL database server, the following happens, given that the data directory of the server is empty:
a) The server is initialized. b) An SSL certificate and key files are generated in the data directory. c) The validate_password plugin is installed and enabled. d) A superuser account ‘root’@’localhost is created. The initial root password created can be found in the error log file. You can get the password by issue the following command :
# sudo grep 'temporary password' /var/log/mysqld.log
2016-06-19T23:08:09.439963Z 1 [Note] A temporary password is generated for root@localhost: sj-mMM;o%6Ll
8. Harden MySQL Server
Run the mysql_secure_installation script to address several security concerns in a default MySQL installation.
You will be given the choice to change the MySQL root password, remove anonymous user accounts, disable root logins outside of localhost, and remove test databases. It is recommended that you answer yes to these options.
# sudo mysql_secure_installation
Securing the MySQL server deployment.
Enter password for user root:
The 'validate_password' plugin is installed on the server.
The subsequent steps will run with the existing configuration
of the plugin.
Using existing password for root.
Estimated strength of the password: 50
Change the password for root ? ((Press y|Y for Yes, any other key for No) : yes
Re-enter new password:
Estimated strength of the password: 50
Do you wish to continue with the password provided?(Press y|Y for Yes, any other key for No) : y
By default, a MySQL installation has an anonymous user,
allowing anyone to log into MySQL without having to have
a user account created for them. This is intended only for
testing, and to make the installation go a bit smoother.
You should remove them before moving into a production
Remove anonymous users? (Press y|Y for Yes, any other key for No) : y
Normally, root should only be allowed to connect from
'localhost'. This ensures that someone cannot guess at
the root password from the network.
Disallow root login remotely? (Press y|Y for Yes, any other key for No) : no
By default, MySQL comes with a database named 'test' that
anyone can access. This is also intended only for testing,
and should be removed before moving into a production
Remove test database and access to it? (Press y|Y for Yes, any other key for No) : y
- Dropping test database...
- Removing privileges on test database...
Reloading the privilege tables will ensure that all changes
made so far will take effect immediately.
Reload privilege tables now? (Press y|Y for Yes, any other key for No) : y
389 Directory Server (previously Fedora Directory Server) is an open source enterprise class LDAP server for Linux. It is developed by Red Hat community-supported Fedora Project. The name 389 is derived from the port number for LDAP.
In this article we will guide you through the steps on how to install and setup 389 directory server on CentOS 7.
Steps to Install and Setup 389 Directory Server on CentOS 7
1. Turn off selinux :
Change SELINUX to disabled then reboot the server :
# 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.
# SELINUXTYPE= can take one of three two values:
# targeted - Targeted processes are protected,
# minimum - Modification of targeted policy. Only selected processes are protected.
# mls - Multi Level Security protection.
2. Perform basic performance and Security tuning for LDAP server :
This program will set up the 389 Directory and Administration Servers.
It is recommended that you have "root" privilege to set up the software.
Tips for using this program:
- Press "Enter" to choose the default and go to the next screen
- Type "Control-B" then "Enter" to go back to the previous screen
- Type "Control-C" to cancel the setup program
Would you like to continue with set up? [yes]:
Your system has been scanned for potential problems, missing patches,
etc. The following output is a report of the items found that need to
be addressed before running this software in a production
389 Directory Server system tuning analysis version 23-FEBRUARY-2012.
NOTICE : System is x86_64-unknown-linux3.10.0-327.4.5.el7.x86_64 (2 processors).
Would you like to continue? [yes]:
Choose a setup type:
Allows you to quickly set up the servers using the most
common options and pre-defined defaults. Useful for quick
evaluation of the products.
Allows you to specify common defaults and options.
Allows you to specify more advanced options. This is
recommended for experienced server administrators only.
To accept the default shown in brackets, press the Enter key.
Choose a setup type :
Enter the fully qualified domain name of the computer
on which you're setting up server software. Using the form
To accept the default shown in brackets, press the Enter key.
Warning: This step may take a few minutes if your DNS servers
can not be reached or if DNS is not configured correctly. If
you would rather not wait, hit Ctrl-C and run this program again
with the following command line option to specify the hostname:
Computer name [centos72.ehowstuff.local]:
The servers must run as a specific user in a specific group.
It is strongly recommended that this user should have no privileges
on the computer (i.e. a non-root user). The setup procedure
will give this user/group some permissions in specific paths/files
to perform server-specific operations.
If you have not yet created a user and group for the servers,
create this user and group using your native operating
System User [nobody]: ldap
System Group [nobody]: ldap
Server information is stored in the configuration directory server.
This information is used by the console and administration server to
configure and manage your servers. If you have already set up a
configuration directory server, you should register any servers you
set up or create with the configuration server. To do so, the
following information about the configuration server is required: the
fully qualified host name of the form
.(e.g. hostname.example.com), the port number
(default 389), the suffix, the DN and password of a user having
permission to write the configuration information, usually the
configuration directory administrator, and if you are using security
(TLS/SSL). If you are using TLS/SSL, specify the TLS/SSL (LDAPS) port
number (default 636) instead of the regular LDAP port number, and
provide the CA certificate (in PEM/ASCII format).
If you do not yet have a configuration directory server, enter 'No' to
be prompted to set up one.
Do you want to register this software with an existing
configuration directory server? [no]:
Please enter the administrator ID for the configuration directory
server. This is the ID typically used to log in to the console. You
will also be prompted for the password.
Configuration directory server
administrator ID [admin]:
The information stored in the configuration directory server can be
separated into different Administration Domains. If you are managing
multiple software releases at the same time, or managing information
about multiple domains, you may use the Administration Domain to keep
If you are not using administrative domains, press Enter to select the
default. Otherwise, enter some descriptive, unique name for the
administration domain, such as the name of the organization
responsible for managing the domain.
Administration Domain [ehowstuff.local]:
The standard directory server network port number is 389. However, if
you are not logged as the superuser, or port 389 is in use, the
default value will be a random unused port number greater than 1024.
If you want to use port 389, make sure that you are logged in as the
superuser, that port 389 is not in use.
Directory server network port :
Each instance of a directory server requires a unique identifier.
This identifier is used to name the various
instance specific files and directories in the file system,
as well as for other uses as a server instance identifier.
Directory server identifier [centos72]:
The suffix is the root of your directory tree. The suffix must be a valid DN.
It is recommended that you use the dc=domaincomponent suffix convention.
For example, if your domain is example.com,
you should use dc=example,dc=com for your suffix.
Setup will create this initial suffix for you,
but you may have more than one suffix.
Use the directory server utilities to create additional suffixes.
Suffix [dc=ehowstuff, dc=local]:
Certain directory server operations require an administrative user.
This user is referred to as the Directory Manager and typically has a
bind Distinguished Name (DN) of cn=Directory Manager.
You will also be prompted for the password for this user. The password must
be at least 8 characters long, and contain no spaces.
Press Control-B or type the word "back", then Enter to back up and start over.
Directory Manager DN [cn=Directory Manager]:
The Administration Server is separate from any of your web or application
servers since it listens to a different port and access to it is
Pick a port number between 1024 and 65535 to run your Administration
Server on. You should NOT use a port number which you plan to
run a web or application server on, rather, select a number which you
will remember and which will not be used for anything else.
Administration port :
The interactive phase is complete. The script will now set up your
servers. Enter No or go Back if you want to change something.
Are you ready to set up your servers? [yes]:
Creating directory server . . .
Your new DS instance 'centos72' was successfully created.
Creating the configuration directory server . . .
Beginning Admin Server creation . . .
Creating Admin Server files and directories . . .
7. Start the dirsrv admin service and dirsrv instance :
Munin is open source and free software for monitoring computer system, network monitoring and application infrastructure monitoring software. Munin offers monitoring and alerting for servers, switches, applications, and services.
Munin can help system administrators to analyze the trend of the computer system whether it is experiencing problems or not. It can be an easier alternative to the popular open-source software zabbix monitoring.
In this article, I will explain how you can monitor your linux CentOS with Munin and the simple steps to install and setup Munin on CentOS 7.
5. You also have optional to change the munin node hostname :
# vim /etc/munin/munin-node.conf
Change to :
6. Next go to the Apache virtual host configuration file to add the permission to access your network.
# vim /etc/httpd/conf.d/munin.conf
Add network segment that you allow to access to the CentOS server.
Deny from all
Allow from 127.0.0.1 192.168.0.0/24
7. Munin statistics page shall be protected by a username and password. We can add the new user (admin) and password to /etc/munin/munin-htpasswd with htpasswd command line. So we have to setup basic Apache authentication before we can start access the munin statistic page.
# htpasswd /etc/munin/munin-htpasswd admin
Re-type new password:
Adding password for user admin
Many have asked me, did Zimbra Collaboration (ZCS) 8.6.0 Patch4 will include Patch1 to Patch3? Actually, if you read the release notes document, the answer is there. ZCS patches are cumulative, meaning ZCS 8.6.0 Patch4 includes ZCS 8.6.0 Patch3, ZCS 8.6.0 Patch2 and ZCS 8.6.0 Patch1. These patch release notes provide information about the Zimbra Collaboration (ZCS) 8.6.0 Patch4, including the enhancements, bug fixes, security fixes, considerations, Known issues, preparation before installing the Patch, step to install the patch, example of the Patch script and revision history information. This step to install zimbra patch has been tested on RHEL6, CentOS6, Oracle Linux 6, RHEL7, CentOS7 and Oracle Linux 7.
In release notes document (preparation before patch), one of the steps we need to take into consideration is to perform a full backup before applied any patch. This is because there is no automatic roll-back if anything goes wrong. If your environment is currently using VMware Vsphere, you can do a virtual machine snapshot before start installing any patch.
How to Install Zimbra Patch4 CentOS / RHEL
1. Before begin, you should get ready the following:
a) Zimbra Collaboration 8.6.0 GA installed (Tested in RHEL6/CentOS6/OL6/RHEL7/CentOS7/OL7)
Most system administrators have applied linux login banner on their servers. The purpose of this linux login banner is to show some messages or warnings when ssh session connected and before entry. The message displayed in the linux login banner is dedicated either to the system administrator who wants to perform routine system maintenance or intruders who want to launch brute force attacks on the server.
Linux Login Banner on CentOS 6 / CentOS 7 / RHEl 7 / Oracle Linux 7
To enable this in ssh you have to follow this simple steps:
1. Create a /etc/mybanner file and fill it with your desired message as below
# vi /etc/mybanner
Unauthorized access to this machine is prohibited
Only authorized System Administrator can access to this system
Press if you are not an authorized user
Save and Quit the mybanner file.
Optionally you can give warning as below if it is involved a server with highly confidential information:
This service is restricted to authorized System Administrator only. All activities on this system are logged. Unauthorized access will be fully investigated and reported to the appropriate law enforcement agencies.
2. Edit /etc/ssh/sshd_config, to look like this Banner /etc/mybanner
-c, –comment COMMENT Add a value, such as a full name, to the GECOS field.
-g, –gid GROUP Specify the primary group for the user account.
-G, –groups GROUPS Specify a list if supplementary groups for the user account.
-a, –append Used with the -G option to append the user to the supplemental groups mentioned without removing the user from other groups.
-d, –home HOME_DIR Specify a new home directory to a new location. Must be used with the -d option.
-m, –move-home Move a user home directory to a new location. Must be used with the -d option.
-s, –shell SHELL Specify a new login shell for the user account.
-L, –lock Lock a user account.
-U, –unlock Unlock a user account.
2. Deleting a User from an Linux System.
a) Get userdel manual :
# man userdel
userdel - delete a user account and related files
b) userdel username removes the user from /etc/passwd, but leaves the home directory intact by default. Proper command to remove the user’s account, user’s home directory and mail spool as part of the deletion process :
# userdel --remove ehowstuff
# userdel -r ehowstuff
Warning : When a user is removed with userdel without the -r option specified, the system will have files that are owned by an unassigned user ID number. This can also happen when files created by a deleted user exist outside their home directory. This situation can lead to information leakage and other security issues.
This post assume that you have just finished the Gnome GUI installation on CentOS 7 by using “yum groupinstall “GNOME Desktop” “Graphical Administration Tools” -y” command. Previously you are running a minimum CentOS 7, only with command line via terminal. But after you reboot the server you get the following screen.
Initial setup of CentOS Linux 7 (core)
1) [x] Creat user 2) [!] License information
(no user will be created) (license not accepted)
Please make your choice from above ['q' to quit | 'c' to continue | 'r' to refresh]:
To fix the issue, you have to perform the following :
a) Press 1 b) Press 2 in order to change [ ] to [x] in front of 2) I accept the license agreement c) Press q d) Accept license menu does not prompt anymore at boot.