DNS, also known as name server, is a service on the Internet that provides mapping between IP addresses and domain names and vice versa. DNS maintains a database of names and related IP addresses. When an application queries with a domain name, DNS responds with a mapped IP address. Applications can also ask for a domain name by providing an IP address.
DHCP is a service used to automatically assign network configuration to client systems. DHCP can be used as a handy tool when you have a large pool of systems that needs to be configured for network settings. Plus, when you need to change the network configuration, say to update a DNS server, all you need to do is update the DHCP server and all the connected hosts will be reconfigured with new settings. Also, you get reliable IP address configuration that minimizes configuration errors and address conflicts.
When you install Ubuntu server, its network setting defaults to dynamic IP addressing, that is, the network management daemon in Ubuntu searches for a DHCP server on the connected network and configures the network with the IP address assigned by DHCP. Even when you start an instance in the cloud, the network is configured with dynamic addressing using the DHCP server setup by the cloud service provider. In this article, you will learn how to configure the network interface with static IP assignment.
Getting ready
When we are talking about server systems, networking is the first and most important factor. If you are using an Ubuntu server in a cloud or virtual machine, you generally don't notice the network settings, as they are already configured with various network protocols. However, as your infrastructure grows, managing and securing the network becomes the priority.
In this article, we will cover the following recipes:
In this recipe, we will look at ways to make user profiles more secure.
How to do it...
Follow these steps to secure the user account:
Set a strong password policy with the following steps:
Open the /etc/pam.d/common-password file with GNU nano:
$ sudo nano /etc/pam.d/common-password
Find the line similar to this:
password [success=1 default=ignore] pam_unix.so obscure sha512
Add minlen to the end of this line:
In this recipe, you will see how to set up secure public key authentication.
Getting ready
You might need root privileges for certain tasks.
How to do it...
Follow these steps to set up public key authentication:
Add a new user. You can skip this step if you have already created a user:
$sudo adduser john
Log in as john and change to the home directory with cd ~/:
Create a .ssh directory if it doesn't already exist:
$ mkdir .ssh
Ubuntu is a multiuser and multi-process operating system. If a single user or process is consuming too many resources, other processes might not be able to use the system. In this recipe, you will see how to set resource limits to avoid such problems.
Getting ready
User account with root privileges is required.
How to do it...
Following are the steps to set the resource limits:
Check the CPU use limit with $ulimit –t.
To set new limit, open limits.conf with the following command:
When you create a new Ubuntu server in the cloud, by default you get the root account. This account has full system access with no restrictions at all and should only be used for administrative tasks. You can always create a new user account with fewer privileges. But there are times when you need extra root privileges to add a new user or change some system setting. You can use the sudo command to temporarily get extra privileges for a single command. In this recipe, you will see how to grant sudo privileges to a newly created user.
Getting ready
We have created users and groups. In this recipe, you will work with default file permissions for users and groups, as well as see how to modify those permissions.
Getting ready
Create two users, user1 and user2. Create new group editor and add user1 and user2 as members.
How to do it…
Follow these steps to manage file permissions, follow these steps:
To change groups for files and directories:
Log in with user1.
Create a new directory documents under home:
