Postfix TLS Setup

Configure Postfix to allow secure connections (Short Version)

openssl genrsa -des3 -out mail.domain.tld.key 2048
chmod 600 mail.domain.tld.key
openssl req -new -key mail.domain.tld.key -out mail.domain.tld.csr
openssl x509 -req -days 365 -in mail.domain.tld.csr -signkey mail.domain.tld.key -out mail.domain.tld.crt
openssl rsa -in mail.domain.tld.key -out mail.domain.tld.key.nopass
mv mail.domain.tld.key.nopass mail.domain.tld.key
openssl req -new -x509 -extensions v3_ca -keyout cakey.pem -out cacert.pem -days 3650
chmod 600 mail.domain.tld.key
chmod 600 cakey.pem
mv mail.domain.tld.key /etc/ssl/private/
mv mail.domain.tld.crt /etc/ssl/certs/
mv cakey.pem /etc/ssl/private/
mv cacert.pem /etc/ssl/certs/
postconf -e ‘smtpd_tls_auth_only = no’
postconf -e ‘smtp_use_tls = yes’
postconf -e ‘smtpd_use_tls = yes’
postconf -e ‘smtp_tls_note_starttls_offer = yes’
postconf -e ‘smtpd_tls_key_file = /etc/ssl/private/mail.domain.tld.key’
postconf -e ‘smtpd_tls_cert_file = /etc/ssl/certs/mail.domain.tld.crt’
postconf -e ‘smtpd_tls_CAfile = /etc/ssl/certs/cacert.pem’
postconf -e ‘smtpd_tls_loglevel = 1’
postconf -e ‘smtpd_tls_received_header = yes’
postconf -e ‘smtpd_tls_session_cache_timeout = 3600s’
postconf -e ‘tls_random_source = dev:/dev/urandom’
postconf -e ‘myhostname =’


Mysql Commands


Create a Mysql Database
$ mysql -u adminusername -p
mysql> CREATE DATABASE db_name;
mysql> mysql> GRANT ALL PRIVILEGES ON db_name.* TO “db_user”@”localhost” IDENTIFIED BY “passsword”;
mysql> EXIT

Backup a Mysql Database
mysqldump -u db_user -p db_name > dumped_db.sql

Restore a Mysql Database
mysql -p -u db_user db_name < dumped_db.sql

NTP on CentOS

You can easily install NTP (Network Time Protocol, a means of transmitting time signals over a computer network) using the yum command under Red Hat or CentOS/Fedora Linux server or workstation based systems. You need to install the following packages:


  1. ntp : ntpd server which continuously adjusts system time and utilities used to query and configure the ntpd daemon.
  2. ntpdate : Utility to set the date and time via NTP.
  3. ntp-doc : NTP documentation

Procedure: Setup NTPD on CentOS Linux

Open the terminal or login over the ssh session. You must login as as the root user. Type the following yum command to install ntp
# yum install ntp ntpdate ntp-doc

Turn on service, enter:
# chkconfig ntpd on

Synchronize the system clock with server (use this command only once or as required):
# ntpdate

Start the NTP server. The following will continuously adjusts system time from upstream NTP server. No need to run ntpdate:
# /etc/init.d/ntpd start

Configure ntpd (optional)

Edit /etc/ntp.conf, enter:
# vi /etc/ntp.conf
Set public servers from the project: