Sunday, February 21, 2010

Debian 2

debian-installer is the installer used for installing Debian. The language selected during debian-installer is not the system language. It is simply for the installation process. However, the country list given on the next page would be based on the language selected.
The netinst image provides minimal packages. It is the base install. The extra packages will be downloaded from internet mirrors during the later parts of installation.

During installation, you would be given the choice to partition the disk. LVM stands for Logical Volume Management. LVM is required to configure RAID. It is not a good idea for all files to be on the same partition for a server. It is the most ideal to give a partition for each folder (home, usr, var, tmp) as suggested by the installer.

Ext3 is the newest available file system available on Linux. Ext3 is a journaling file system. Partition is the basic allocation unit for hard drives. File systems sit on top of partitions to provide features for users.

A journaling file system is a file system that keeps track of the changes it is about to make in a journal. Should a system crash occur during writing, it is easier to read from the journal and undo the damage. A journaling file system is less likely to become corrupted. The NTFS used in Windows is also a journaling file system, unlike its predecessor, the FAT file system.

For my purpose I am going to leave the system to use only the standard system. This will allow practice on installation and activation of basic services. After the packages are properly configured, GRUB boot loader will be installed on the hard disk. GRUB will be installed in the master boot record.

During boot, you will see two or more choices depending on whether your system is clean. Single-user mode is for emergency purposes where the administrator backs up or recovers a system.

Once the system is properly booted, you will be brought to the tty1 login. You can log in as either root or the non-privileged user from here. We can start by checking the version of Debian with the following command:
cat /etc/debian_version

We can now check the various file systems in place from the root folder (\) using:
df -h

You can check for any listeners using the following commands:
netstat -ntl
netstat -nulp

-ntl will show TCP listeners, while -nulp will show UDP listeners. From a base installation you will only see the system listening to UDP port 68 which is for DHCP.

To check the system's network status, use the following command:

You can check the nameservers configured using:
cat /etc/resolv.conf

We can reveal the IP addresses returned by the DNS using:
dig www.google.com

To find out what programs are installed, use:
dpkg -l | more

To do a filter of the output, use the grep pipe. For example, to show lines with "ssh" in it.:
dpkg -l | grep ssh

Multiple ttys are configured, so you can do a CTRL+ALT+F# where # is the tty number you wish to go. tty7 is for GUI, which isn't installed.

We can check the tty consoles configured using:
cat /etc/inittab

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