CentOS 7

How To Change Time/Date In Linux From Command Prompt

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These commands work with CentOS 6.5. The commands for CentOS 7 are similar and you should be able to figure them out if you start with these commands.

Only change time not date:

To only set the time use like this:

# date -s hh:mm:ss

Update Hardware clock:

To sync the hardware clock to the current system clock:

# hwclock –systohc
# hwclock –systohc –utc
***** use the second option if you use UTC.

Set Hardware clock manually:

To know the current time of the hardware clock:

# hwclock –show
Tue Nov  4 22:13:40 2003  -0.684660 seconds

To set the hw clock manually:

# hwclock –set –date=”09/21/2005 14:23:23″


We run into power issues from time to time and our servers have been known to lose their time. The hardware time may not have been changed and the system often synchronizes off of the hardware clock, especially following a power cycle.

Below are the steps I performed to 1. change the system clock to the correct time and then 2. synchronize the hardware clock up to the system clock.

[root@ ~]# date -s 16:30:00
Mon Jan 26 16:30:00 CST 2015
[root@ ~]# date
Mon Jan 26 16:30:05 CST 2015
[root@ ~]# hwclock –show
Mon 26 Jan 2015 03:09:58 PM CST -0.188457 seconds
[root@ ~]# hwclock –systohc –utc
[root@ ~]# hwclock –show
Mon 26 Jan 2015 04:35:40 PM CST -0.616988 seconds

CentOS 7

Another MySQL daemon already running with the same unix socket

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When you run into this problem, you can delete or move the mysql.sock file.

In this instance, we just removed the file:

 rm -rf /var/lib/mysql/mysql.sock

In this instance, we just moved it to a .bak file.

mv var/lib/mysql/mysql.sock /var/lib/mysql/mysql.bak
service mysqld restart

Restarting the service creates a new entry called mqsql.sock

How To Install Zimbra 8.6 on Linux CentOS 7.0

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This post will walk you through the steps of installing Zimbra 8.6 on CentOS 7.0 and the instructions should work the same for RHEL 7.

There were some CentOS services that were deprecated in 7.0. Two particular that I was comfortable with. Iptables and Ifconfig.

Instructions for installing the iptables feature on CentOS 7.0 can be found here.
Instructions for installing the ifconfig feature on CentOS 7.0 can be found here.


Configure DNS Entries on your local DNS server
Setup DNS A Record
Ensure you have a Reverse lookup zone
Setup MX Record

Configure Host Settings
Login as root user
su root

Install pre-requisites
yum install wget make nc sudo sysstat libtool-ltdl glibc perl-core ntp unzip libaio

Set hostname
hostname mail.yourdomain.com

Edit hostname file
nano /etc/hostname

Add Hosts Entries
nano /etc/hosts

By default, this is what’s present:   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

Comment out (required for disabling ipv6)
#::1               localhost localhost.localdomain localhost6 localhost6.localdomain6

Add the following:
<server IP>   mail.yourdomain.com MAIL
<local DNS IP> mail.yourdomain.com

Press “Ctl+X” to exit
Select “Y” to save changes
Press “Enter” to get back to CL


Disable other services and firewall
service postfix stop
chkconfig postfix off
service ip6tables stop
chkconfig ip6tables off


Enter this at command line:
setenforce 0

Update selinux config file
nano /etc/selinux/config

Press “Ctl+X” to exit
Select “Y” to save changes
Press “Enter” to get back to CL


Completely disable the ipv6 module
To completely disable IPv6 in your system, all you have to do is save the following line in a file inside/etc/modprobe.d/.
cd /etc/modprobe.d/
nano disable-ipv6

Add this to the new file:
ipv6 /bin/true

Press “Ctl+X” to exit
Select “Y” to save changes
Press “Enter” to get back to CL


Configure iptables to allow email server traffic
nano /etc/sysconfig/iptables

Add the following

-A INPUT -m state –state NEW -m tcp -p tcp –dport 25 -j ACCEPT
-A INPUT -m state –state NEW -m tcp -p tcp –dport 80 -j ACCEPT
-A INPUT -m state –state NEW -m tcp -p tcp –dport 110 -j ACCEPT
-A INPUT -m state –state NEW -m tcp -p tcp –dport 143 -j ACCEPT
-A INPUT -m state –state NEW -m tcp -p tcp –dport 443 -j ACCEPT
-A INPUT -m state –state NEW -m tcp -p tcp –dport 389 -j ACCEPT
-A INPUT -m state –state NEW -m tcp -p tcp –dport 465 -j ACCEPT
-A INPUT -m state –state NEW -m tcp -p tcp –dport 993 -j ACCEPT
-A INPUT -m state –state NEW -m tcp -p tcp –dport 995 -j ACCEPT
-A INPUT -m state –state NEW -m tcp -p tcp –dport 7071 -j ACCEPT
-A INPUT -m state –state NEW -m tcp -p tcp –dport 7025 -j ACCEPT

Press “Ctl+X” to exit
Select “Y” to save changes
Press “Enter” to get back to CL


Download Zimbra Installation
Latest Version 8.6.0 GA Release


Move Zimbra Download File To New VM
I downloaded the package to my local Windows workstation. From a Windows machine, an additional tool is required.  There are a few options but I downloaded and used WinSCP v 5.5.2. It works.

Copy downloaded Zimbra .tgz file (in this case zcs-8.6.0_GA_1153.RHEL7_64.20141215151110.tgz) from local workstation to /tmp/ directory on new VM. Simple click, drag and drop copies the file.


Decompress and Install Zimbra
From the CL, decompress the file by running the following command:
tar xzf zcs-8.6.0_GA_1153.RHEL7_64.20141215151110.tgz


Navigate to the newly created/renamed directory:
cd zcs-8.6.0_GA_1153.RHEL7_64.20141215151110

su root

To uninstall (which you will need to do if you run into issues with the installation)
./install.sh -u


Change admin password to a more complex password  (this is the admin console login)
“r” to return to previous screen
“a” to apply the changes
Yes to save config to file
Enter to save to default config file
Yes to modify system

Save config in file: [/opt/zimbra/config.23168]
Moving /tmp/zmsetup01072015-114839.log to /opt/zimbra/log

When complete, change user to zimbra
su – zimbra

Check status of Zimbra
zmcontrol status


Verify Mail Server is Operational
Open a browser and navigate to https://mail.yourdomain.com (webmail console)

Login using admin and password


Open a browser and navigate to https://mail.yourdomain.com:7071 (admin console)
Login using admin and password


Once logged into your admin panel, continue configuration
Configure->Global Settings->MTA

Add hostname of your server (in this case, mail)

Added New Domain yourdomain.com

Setup admin@yourdomain.com with Global Admin rights

Deleted domain created at setup mail.yourdomain.com

Create user accounts

Create distribution lists

Create aliases



To put this server into production, you will need to:
1. Contact your ISP and request a PTR record or reverse DNS.
2. Acquire a certificate from a trusted source.
3. Setup an MX record with your domain registrar


Rebranding is limited with the OSS license. Ensure your read and understand the licensing agreement.

Favicon Locations


Changing the Page Title

As zimbra user (su – zimbra):
vi /opt/zimbra/jetty/webapps/zimbra/WEB-INF/classes/messages/ZmMsg.properties
[change value for zimbraTitle = <new value>]
vi /opt/zimbra/jetty/webapps/zimbra/WEB-INF/classes/messages/ZhMsg.properties
[change value for zimbraTitle = <new value>]

The first is for the advanced client and the second is for the basic client.
You will need to restart jetty and clear your browser cache/restart browser to see change take effect

As zimbra user,
zmmailboxdctl restart


You will most likely run into some issues depending on your environment so good luck!