Centos on Mini Fish

How to Configure CentOS 6 NFS Service

Thu, 05 Jun 2014 22:21:06 +0800

Server Side

Disable SeLinux
Edit the configuration file:

vi /etc/selinux/config

Modify as follows:

#SELINUX=enforcing    # Comment out
#SELINUXTYPE=targeted # Comment out
SELINUX=disabled      # Add this line

Then reboot the system:

reboot  # Restart the system

Create a Directory
Using the root user, create a directory named /nfs. Note: It’s best to check which partition has the most space by running df, as the root (/) partition may not have the most space. In some automatic partitioning setups, the /home partition may have the most space.
Install NFS Utilities and RPC Bind
```
yum -y install nfs-utils rpcbind
```

Enable Services at Boot

chkconfig nfs on
chkconfig rpcbind on
chkconfig nfslock on

Configure Exports
Edit the NFS exports file:

vi /etc/exports

Add the following line:

/home/nfs 192.168.1.0/24(rw,sync,no_all_squash)

Start NFS Services

service rpcbind start
service nfs start
service nfslock start
exportfs -a

Configure NFS Ports
Edit the NFS configuration file:

vi /etc/sysconfig/nfs

Uncomment the following lines:

LOCKD_TCPPORT=32803
LOCKD_UDPPORT=32769
MOUNTD_PORT=892

Restart NFS Services

service rpcbind restart
service nfs restart
service nfslock restart

Verify RPC Services
```
rpcinfo -p localhost
```
Note down the ports and their types.

Configure Firewall Rules
Adjust the IP range according to your network:

iptables -I INPUT -m state --state NEW -p tcp -m multiport --dport 111,892,2049,32803 -s 192.168.0.0/24 -j ACCEPT
iptables -I INPUT -m state --state NEW -p udp -m multiport --dport 111,892,2049,32769 -s 192.168.0.0/24 -j ACCEPT

Save Firewall Rules
Test from the client side. If successful, save the iptables configuration:
```
service iptables save
```

Client Side

Create Mount Point
```
mkdir /nfs
```
Check RPC Services on Server
```
rpcinfo -p [server_ip]
```
Show NFS Exports
```
showmount -e [server_ip]
```

Mount NFS Share

mount -t nfs -o soft,intr,bg,rw [server_ip]:/home/nfs /nfs

Unmount NFS Share
```
umount /nfs
```
Configure Automatic Mounting
Edit the fstab file:
```
vi /etc/fstab
```
Add the following line:
```
[server_ip]:/home/nfs /nfs nfs soft,intr,bg,rw 0 0
```

How to Configure CentOS KVM Network Bridging Mode

Thu, 05 Jun 2014 22:21:06 +0800

What Is Bridging

Bridging highly simulates a network card, making the router believe that the virtual machine’s network card truly exists. Personally, I feel it’s similar to resistors connected in parallel, whereas NAT (another common virtual machine network connection method) is more like parasitizing on the host’s network card.

Why Use Bridging

It allows you to treat the virtual machine as a completely independent machine, enabling mutual access with the external network (which is not possible with NAT).

How to Configure Bridging

In CentOS 6, refer to the command-line method in this article.

We don’t use the GUI method because:

We’re unsure which options to fill in on the last screen.
We don’t know how to reset if we make a wrong selection.

Command-line steps:

Check if bridge-utils is installed:
```
rpm -q bridge-utils
```
Usually, it’s already installed. If not, install it:
```
su -
yum install bridge-utils
```

Verify your network interfaces:

Run ifconfig to ensure you have at least three network interfaces:

eth0      Link encap:Ethernet  HWaddr 00:18:E7:16:DA:65
          inet addr:192.168.0.117  Bcast:192.168.0.255  Mask:255.255.255.0
          inet6 addr: fe80::218:e7ff:fe16:da65/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:556 errors:0 dropped:0 overruns:0 frame:0
          TX packets:414 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:222834 (217.6 KiB)  TX bytes:48430 (47.2 KiB)
          Interrupt:16 Base address:0x4f00

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:8 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:480 (480.0 b)  TX bytes:480 (480.0 b)

virbr0    Link encap:Ethernet  HWaddr 52:54:00:2A:C1:7E
          inet addr:192.168.122.1  Bcast:192.168.122.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:13 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 b)  TX bytes:2793 (2.7 KiB)

Navigate to the network scripts directory:

su –
cd /etc/sysconfig/network-scripts

Bring down the eth0 interface:
```
ifdown eth0
```
This step is crucial and must be performed locally. When I first configured this, I didn’t shut down the network (since I was working remotely). I didn’t realize that updating the ifcfg-eth0 configuration without restarting the network would immediately apply changes, resulting in loss of network connectivity.
Edit ifcfg-eth0:

In the ifcfg-eth0 file, include:
```
DEVICE=eth0
ONBOOT=yes
BRIDGE=br0
```
Keep only these three lines in the file. There’s no need to configure an IP address here. Bridging seems to replace the original network card with the bridge, so you can delegate the configuration to the bridge.

Create a new file ifcfg-br0:

DEVICE=br0
ONBOOT=yes
TYPE=Bridge
BOOTPROTO=static
IPADDR=xxx.xxx.xxx.xxx   # Use the IP you originally had in ifcfg-eth0
GATEWAY=xxx.xxx.xxx.xxx  # Your gateway address
NETMASK=255.255.255.0    # Your netmask
DNS1=xxx.xxx.xxx.xxx     # Your primary DNS server
DNS2=xxx.xxx.xxx.xxx     # Your secondary DNS server (if any)
STP=on
DELAY=0

Note: Replace xxx.xxx.xxx.xxx with your actual network settings.

Bring up the interfaces:
```
ifup br0
ifup eth0
```
Verify the bridge interface:

Check ifconfig to ensure that br0 is now present.
Update firewall rules:

Edit /etc/sysconfig/iptables and add:
```
-A INPUT -i br0 -j ACCEPT
```
(This is a general example; you may need to adjust it based on your specific firewall configuration.)
Restart the firewall:
```
service iptables restart
```
Configure bridging in virt-manager:

When creating a new virtual machine using virt-manager, you can now select br0 for the network interface. Without this bridge, the bridging option would not be available.

Note: When configuring the IP inside the virtual machine, be sure to specify the GATEWAY. Otherwise, the virtual machine will only be able to access the internal network and not the external network. At this point, the virtual machine won’t automatically discover the gateway.

How to Install CentOS as a Virtualization Host

Thu, 05 Jun 2014 22:21:06 +0800

Installation Process

Installed Version: CentOS 6.3

Using Win32DiskImager to create a USB flash drive image was unsuccessful; installing from an external USB optical drive was successful.
During the installation process, make sure to select the “Virtual Host” installation mode.
The rest can be set to default or slightly modified, such as choosing the time zone.
After installation, it will include the KVM suite and SSH.

Installation Notes

No internet connection is needed throughout the process, which is much better than Debian and Ubuntu.
You’re not forced to set up a non-root user.
Before installation, be sure to check whether your CPU supports virtualization and enable the motherboard’s virtualization setting. If the motherboard supports virtualization but doesn’t have a virtualization option, you can still use virtualization as it’s definitely enabled by default. There’s a saying that Intel CPUs with a ‘K’ cannot perform virtualization. ‘K’ means Intel CPUs that can be overclocked. It seems that faster and newer CPUs are not necessarily better.