Postfix is the default Mailer used in CentOS and Ubuntu. If you are using a residential Internet connection you will possibly need to use the Smarthost option in Postfix to deliver mail. If this is the case, here’s how to do it.

Edit /etc/postfix/main.cf and either edit or add the line:

relayhost = <smarthost>

Replacing with the server you will be using to deliver mail.

After this change, you’ll need to restart Postfix.

$sudo /etc/init.d/postfix restart

With nginx it’s quite easy to add www to your domain name when access your website.

1
2
3
4
5
6

# Add a www to the domain
server {
  listen 80;
  server_name example.com;
  rewrite ^(.*)$ $scheme://www.example.com$1;
}

With this, any request to example.com will be changed to www.example.com.

I have had my Mikrotik RB751G-2HnD in service for a few months now, and it’s been rocking along great.  The cheap price had me a bit skeptical at first, but after seeing some of the reviews and the community around their devices, I was pretty sold.  I purchased the first one to replace a Linksys E4500 wireless router after the Cisco cloud connect upgrade.

I am using the device as a simple home gateway router for my network, with many of the more advanced features disabled.  I do have IPv6 enabled, using a tunnel provided by Hurricane Electric using their tunnel broker service, which has been very stable.  The wireless works great with coverage area expanding beyond what the Linksys provided.

The device supports various VPN connections, but I have yet to test any of this.  Other notable features include a wireless hotspot manager, VLANs and several routing protocols including BGP.

This post is being made for me personal notes. Maybe it will assist others at some point. I am always forgetting the various configuration files involved with setting up networking on a CentOS host. I have decided to document the process I go through each time to help me remember next time. Most of this information comes from various forums, CentOS documentation and the man pages.

Device specific information

A configuration file exists for each interface under /etc/sysconfig/network-scripts/. To change the configuration for eth0 we will need to edit /etc/sysconfig/network-scripts/ifcfg-eth0.

DHCP

Edit the file to match to the following, leave any lines that are not listed below in place

1
2
3

DEVICE=eth0
BOOTPROTO=dhcp
ONBOOT=yes

Static address

To use a static IP address, edit the configuration file as noted below. Again, leave any lines already in the file not listed below in place. The NETWORK, NETMASK, and IPADDR should match your network settings.

1
2
3
4
5
6

DEVICE=eth0
BOOTPROTO=none
ONBOOT=yes
NETWORK=172.24.1.0
NETMASK=255.255.255.0
IPADDR=172.24.1.10

System wide networking information:

Several system wide configuration settings can be found in /etc/sysconfig/network. These include the hostname and gateway as well as the option to disable networking.

Edit /etc/sysconfig/network as necessary to match your local network settings.

1
2
3

NETWORKING=yes
HOSTNAME=server.example.com
GATEWAY=172.24.1.1

DNS server information

Finally, we configure which nameservers to use for DNS resolution. This is set in /etc/resolv.conf and again should match your network settings. The example below will use Google’s Public DNS servers.

1
2

nameserver 8.8.8.8
nameserver 8.8.4.4

After all is set, $service network restart or a reboot for all settings to be applied. If you have custom iptables rules, you will need to adjust them as necessary.

Use a simple psql query to find the location of the data directory

1
2
3
4
5

postgres=# SHOW data_directory;
data_directory
------------------------------
/var/lib/postgresql/8.4/main
(1 row)

1
2
3
4
5

postgres=# select setting from pg_settings where name = 'data_directory';
           setting
------------------------------
 /var/lib/postgresql/8.4/main
(1 row)

If /home is just a folder under / and you have a reason to put this on it’s own partition the process isn’t that difficult. Here is the steps I followed to do this.

First, create the new partition on the drive. I was using LVM, so I created a new logical volume, do whatever makes sense for your system here.

Make a place for the new home partition to be mounted while we transfer files.

mkdir /mnt/newhome
mount -t   /mnt/newhome

Move files from current /home to this new location.

cd /home
cp -ax * /mnt/newhome

Once all the files have copied, remove the old home directory, and mount the new partition in its place.

rm -r /home
mount  -t   /home

Edit /etc/fstab for the new partition, and you’re done.

passwd -l username

passwd -u username

telnet mailserver 110

[root@ms1 ~] # telnet localhost 110
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
+OK POP3 localhost v2001.78rh server ready
USER username
+OK User name accepted, password please
PASS password
+OK Mailbox open, 1 messages
QUIT
+OK Sayonara
Connection closed by foreign host.

ping6 -c 2 -I eth0 ff02::1

ip -f inet6 neigh