Work No. 1 Samba. What is Samba?

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1 Work No. 1 Samba What is Samba? Samba is an implementation of a Server Message Block (SMB) protocol server that can be run on almost every variant of UNIX in existence. Samba is an open source project, just like Linux. The entire code is written in C so it is easily portable to all flavors of UNIX. Samba is a tool for the peaceful coexistence of UNIX and Windows on the same network on the level of File and Print sharing over the NetBIOS protocol. It allows UNIX systems to move into a Windows Network Neighborhood without causing a mess. With Samba, UNIX servers are acting as any other Windows server, offering its resources to the SMB clients. Recently SMB was renamed by Microsoft to Common Internet File System (CIFS). Installing Samba: $ sudo apt-get install samba smbfs Configuring Samba Enabling the user list to add a user: $ sudo gedit /etc/samba/smb.conf Configure Samba - enable users list: ####### Authentication ####### # security = user is always a good idea. This will require a Unix account # in this server for every user accessing the server. See # /usr/share/doc/samba doc/htmldocs/samba HOWTO Collection/ServerType.html # in the samba doc package for details. security = user username map = /etc/samba/smbusers Create Samba user and add to user list file: $ sudo smbpasswd -a <username> $ sudo gedit /etc/samba/smbusers <ubuntu user name> = "<samba user name>" Sharing User's Home directory - edit /etc/samba/smb.conf as below $ sudo gedit /etc/samba/smb.conf #======================= Share Definitions ======================= # Un comment the following (and tweak the other settings below to suit) # to enable the default home directory shares. This will share each # user s home directory as \\server\username [homes] comment = Home Directories

2 browseable = yes # By default, \\server\username shares can be connected to by anyone # with access to the samba server. Un comment the following parameter # to make sure that only username can connect to \\server\username valid users = %S # By default, the home directories are exported read only. Change next # parameter to yes if you want to be able to write to them. writable = yes Access the user's shared home directory - \\ubuntumachine\username Adding shares - Create public directory and set permissions sudo mkdir -p /home/shares/public sudo chown -R root:users /home/shares/public sudo chmod -R ug+rwx,o+rx-w /home/shares/public Configure Samba for each share as below $ sudo gedit /etc/samba/smb.conf [public] comment = Public Share path = /home/shares/public valid users force group = users create mask = 0660 directory mask = 0771 writable = yes

3 Work No. 2 - MAC spoofing MAC spoofing is a technique for changing a factory assigned Media Access Control (MAC) address of a network interface on a networked device. Steps of MAC spoofing: 1. Using ifconfig command in the terminal, the MAC address for eth1 was found to be c4:46:19:80:9d:d9 2. To change MAC address, use the following command. Syntax: sudo ifconfig <device> hw ether <desired new address> sudo ifconfig eth1 hw ether c4:46:19:80:9d:d5 After this the address of the Ethernet will be changed. 3. Use ifconfig again to see the new MAC address.

4 1. nslookup COMMAND: WORK NO. 3 - DNS COMMANDS nslookup is a network administration tool for querying the Domain Name System (DNS) to obtain domain name or IP address mapping or any other specific DNS record. It is also used to troubleshoot DNS related problems. nslookup can operate on both Interactive mode and Non-Interactive mode. Interactive mode allows the user to query the DNS-Server about various host, and domains. Non-Interactive mode allows the user to query the information for a host or domain. Some simple examples of nslookup command and their uses: $ nslookup In the following output, server refers to the IP address of the DNS server. Then the below section provides the IP Address of the domain

5 $ nslookup -query=mx iiitd.ac.in MX (Mail Exchange ) record maps a domain name to a list of mail exchange servers for that domain. The MX record tells that all the mails sent should be routed to the Mail server in that domain.

6 In the above example, we have 5 MX records. The number (10,1,5, 5, 10 ), associated with the MX records tells the preference of mail server. Lower the number, higher the preference. So when a mail is sent first preference will be aspmx.l.google.com. Authoritative Answer vs Non-Authoritative Answer Just notice the keyword Authoritative Answer and Non-Authoritative Answer in the above output. Any answer that originates from the DNS Server which has the complete zone file information available for the domain is said to be authoritative answer. In many cases, DNS servers will not have the complete zone file information available for a given domain. Instead, it maintains a cache file which has the results of all queries performed in the past for which it has gotten authoritative response. When a DNS query is given, it searches the cache file, and return the information available as Non-Authoritative Answer. $ nslookup -type=ns iiitd.ac.in NS (Name Server ) record maps a domain name to a list of DNS servers authoritative for that domain. It will output the name serves which are associated with the given domain.

7 $ nslookup -type=soa iiitd.ac.in SOA record (start of authority), provides the authoritative information about the domain, the e- mail address of the domain admin, the domain serial number etc. Description of different fields: mail addr specifies the mail address of the domain admin. serial sort of revision numbering system. The standard convention is to use YYYYMMYYNN format. refresh specifies ( in seconds ), when the secondary DNS will poll the primary to see if the serial number has been increased. If increased, secondary will make a new request to copy the new zone file. retry specifies the interval to re-connect with the Primary DNS expire specifies the time that the secondary DNS will keep the cached zone file as valid minimum specifies the time that the secondary DNS should cache the zone file.

8 $ nslookup You can also do the reverse DNS look-up by providing the IP Address as argument to nslookup. 2. dig COMMAND: Dig stands for domain information groper. Using dig command you can query DNS name servers for your DNS lookup related tasks. Some simple examples on how to use dig command:- $ dig iiitd.ac.in When you pass a domain name to the dig command, by default it displays the A record (the ipaddress of the site that is queried) as shown below. In this example, it displays the A record of iiitd.ac.in in the ANSWER SECTION of the dig command output.

9 The dig command output has the following sections: Header: This displays the dig command version number, the global options used by the dig command, and few additional header information. QUESTION SECTION: This displays the question it asked the DNS. i.e This is your input. Since we said dig redhat.com, and the default type dig command uses is A record, it indicates in this section that we asked for the A record of the redhat.com website. ANSWER SECTION: This displays the answer it receives from the DNS. i.e this is your output. This displays the A record of redhat.com. Stats section at the bottom displays few dig command statistics including how much time it took to execute this query. Except these there may be authority section and additional section. AUTHORITY SECTION: This displays the DNS name server that has the authority to respond to this query. Basically this displays available name servers of redhat.com ADDITIONAL SECTION: This displays the ip address of the name servers listed in the authority section. Do by yourself: If you want to see only the IP address you can write +short extra. $ dig iiitd.ac.in +short You can just examine is it working or not by yourself.

10 $ dig iiitd.ac.in +nocomments +noquestion +noauthority +noadditional +nostats For most part, all you need to look at is the ANSWER SECTION of the dig command. So, we can turn off all other sections as shown below. +nocomments Turn off the comment lines +noauthority Turn off the authority section +noadditional Turn off the additional section +nostats Turn off the stats section +noanswer Turn off the answer section (Of course, you wouldn t want to turn off the answer section) The following dig command displays only the ANSWER SECTION. Do by yourself:- Instead of disabling all the sections that we don t want one by one, we can disable all sections using +noall (this turns off answer section also), and add the +answer which will show only the answer section. The above command can also be written in a short form as shown below, which displays only the ANSWER SECTION. $ dig iiitd.ac.in +noall +answer Check it by yourself whether it is running or not.

11 $ dig -t MX iiitd.ac.in +noall +answer To query MX records this command is used. Do by yourself:- To query MX records, we can pass MX as an argument to the dig command also. $ dig iiitd.ac.in MX +noall +answer It will give the same answer as above. Check the command by yourself whether it is working or not.

12 $ dig iiitd.ac.in NS +noall +answer To query the NS record as shown below. Do by yourself:- $ dig iiitd.ac.in NS +noall +answer It will give the same answer as above. Check the command by yourself whether it is working or not. $ dig x short To perform a DNS reverse look up using the ip-address using dig -x as shown below For example, if you just have an external IP-address and would like to know the website that belongs to it, do the following. To view the full details of the DNS reverse look-up, remove the +short option. Both the cases have been shown in the picture below.

13 -f attributes of dig can be used to query servers written in a text file with each line consisting of one server address. Do by yourself:- Make a.txt file(eg. Servercheck.txt) in the home folder. Write some server addresses in that text file. One line should consist only one server address. Eg Now execute this command: $ dig -f abc.txt See by yourself what is the output of the command.

14 3. host Command: host is a simple utility for performing DNS lookups. It is normally used to convert names to IP addresses and vice versa. $ host iiitd.ac.in -v attributes of host can be used to get all canonical names of a server. Do by yourself:- $ host -v Execute this command and check the output by yourself.

15 Work No. 4 Monitor Network Bandwidth Bandwidth in computer networking refers to the data rate supported by a network connection or interface. One most commonly used term to express bandwidth is bits per second(bps). Bandwidth represents the capacity of the connection. The greater the capacity, the more likely that greater performance will follow, though overall performance also depends on other factors, such as latency. There are many bandwidth monitoring tools for your network bandwidth. We will study two of them here: 1. iftop command: iftop does for network usage what top does for CPU usage. It listens to network traffic on a named interface and displays a table of current bandwidth usage by pairs of hosts. Install iftop in ubuntu: $ sudo apt-get install iftop This will complete the installation. If you want to run the application you need to use the following command. $ sudo iftop Output looks like below:

16 $ sudo iftop -i wlan0 It will give the result for the LAN interface. The output will look like the following: See the last few lines. TX signifies transmitted data and RX signifies received data. If you open some heavy bandwidth page in your browser ( eg. You can open any youtube video) then you will find the value of TX and RX are changed. Here s a picture that proves it(taken after opening a youtube video).

17 Look the value RX has now changed into MB as the received data is increased due to that youtube video. Check this by yourself:- $ sudo iftop -i wlan0 -B This command will show the size of the data in Bytes rather than bits. $ sudo iftop -i wlan0 -F <any IP address>/<any IP address) -F attributes helps us to see data transmission between two particular IP address. $ sudo iftop i wlan0 -P -P attributes helps us to see the port name of the website rather than their IP address. 2. ipref COMMAND: Tools to measure network performance are very old and have confusing options. iperf was developed as a modern alternative for measuring TCP and UDP bandwidth performance. iperf is a tool to measure maximum TCP bandwidth, allowing the tuning of various parameters and UDP characteristics. Iperf reports bandwidth, delay jitter, datagram loss. Install iperf in ubuntu sudo apt-get install iperf Syntax: iperf [-s/-c host] [options] Example: iperf -s (TCP where your system acts as a server) iperf -c server (TCP where your system acts as a client to query a server) iperf -u -s (UDP) iperf -u -c server (UDP)

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