essential, admin, net
Essential Unix commands
Enter the number of entries in the top level directory. You can use the command ls / and simply count the words.
If you are too lazy to count you can pass the output through the wc command: 'wc -l'
ls / | wc -l
20Edit the file /etc/motd so that it contains the single word Welcome You can use the echo command and redirect the output, or you can use an editor such as vi or nano (similar to pico). If you get a permission denied error ARE YOU SURE YOU ARE ROOT?
On some Windows machines, nano does not seem to like the cursor keys. If (and only if) the cursor keys result in funny characters when using nano, type the following at the prompt and then try nano again:
export TERM=vt102
echo 'Welcome' > /etc/motdGive the uid of the user called "operator".
id operator
uid=11(operator) gid=0(root) groups=0(root)
11Who is the owner of the directory /var/cache/httpd? If you get no information, are you sure you are using "ls" to give the directory information or the contents of the directory instead?
ll /var/cache/httpd
total 0
drwx------. 2 apache apache 6 Nov 14 2016 proxy
apacheGive the name of the first directory (alphabetically) of / that has no read permission for other.
Change the permission of the directory /var/log/httpd so that group and world have execute and read permission.
Change the owner of the file /etc/ntp.conf to operator
Create a directory /root/dropzone It should be set up so that group and other users can save files in the directory, but they cannot read the files that are there. User root must able to read and write the directory.
Create a symbolic link so that the file /usr/share/dict/words appears as /root/words
This is a challenge question. Miss it out if you dont know regular expressions.
Use grep on words to find a word that contains each of the vowels in the correct order. How many such words are there? (you may include words with extra vowels such as adventitious. /root/words
This is a challenge question. Miss it out if you dont know regular expressions.
The word minglingly includes the same four characters (e.g. ingl) repeated. How many such words are there which also begin with lower case "m" (any four character are repeated).
Look in /usr/share/doc and find a directory starting "git-" followed by a version number. In the following questions this directory is referred to as the "git" directory...
How much space is being used by the git directory? Use a command to calculate this, and dont try adding it up yourself! We want the total answer in human readable format (eg 6.2M).
In human readable form (eg 123M) how much disk space is available on the main filesystem?
Remove the entire git directory (it is not used in our tutorials). Now repeat the above calculation for disk space, but this time give the answer in blocks.
Essential Unix Administration
Use sfdisk with block units and find out the partitions which exist in /dev/sda. How many blocks are in the first partition?
Use the pvdisplay command of LVM to discover what physical volume (i.e. which partition) is being managed by LVM. What is the partition being used (PV Name) and what is the volume group name (VG Name)?
Use lvdisplay to discover information about the VG Name found in the previous question. What is the first LV Path which is using the volume group discovered in the previous question?
Using the path discovered in the previous question, look at this path in the /dev directory using a long listing ls command. Assuming this is in fact a soft link, what is the ABSOLUTE device name which this link is pointing to?
For mounting this logical volume, the current method is NOT to use the volume name, or even the device it points to. Instead the device mapper is used, which can support different layers (such as encryption on top of something else). This can be found in /dev/mapper.
Look in /dev/mapper, and find the soft link which points to the device file identified in the previous question. What is the relative name of this link? So if the link was /dev/mapper/gordon, the answer wanted here is "gordon".
Look in the fstab mount table. Find the line which mounts this partition via the mapper device. Where is this partition mounted?
One can also mount things using the filesystem block id (which is the UUID shown in fstab). What block id could you use instead of the mapper mount in this case? It is in a format like ffffff-ffff-fffff-fffff-ffffffffff.
Recall that you discovered the device file in /dev which the LVM mapper entry was soft linked to. What was the major and minor number of this device?
Somewhere in the /proc filesystem there is a file which tells you how much swap space has been allocated to the computer. Find that file and then find out how big in bytes the swap space is. Hint: the information that you require is located within the /proc directory within a file .
What is the process id of rsyslogd? Hint: remember the 'ps aux' command?
Kill rsyslogd using the kill command.
Using systemctl, get the status of the rsyslog service. What is the full path to the systemd configuration file which controls the rsyslog serice?
Look at this configuration file. Find the line which configures the environmental variables of rsyslog (EnvironmentFile). Ignoring the "=" or the "=-" if it exists, what is the environment file for this service?
Restart the rsyslogd services using systemctl. Confirm it is running using the status option.
Start the database. This is called mariadb. This may take a few seconds.
Using systemctl, discover the process id (PID) for the main process. Note, mariadb has many processes, so make sure you select the Main PID.
What user is the owner of this process? Use the "ps" command with the appropriate flags.
If the main pid is the parent of the database, what is the PID of the first child of this parent pid? So if you have the process name for this PID, then pstree might help here.
Set the mariadb to run next time you boot your virtual machine.
Systemctl has an option "list-unit-files", which says which things are enabled for running at boot. How many units are enabled?
How many enabled units are socket units?
Now set the mariadb so that it DOES NOT run next time you boot your virtual machine.
Linux Networking
What is the network device name which connects you to the linuxzoo network? This will have an IPv4 address which starts "10."... Do not type in /dev when you answer this (i.e. make the answer relative to /dev).
What is the broadcast address for this network connection?
What is the netmask in quad dotted format for this network connection?
What is the IP for the default route (i.e. the gateway) for your virtual machine?
Device eth2 is connected to a network for which your virtual machine is the gateway. The network ip is 192.168.1.0 and the netmask is 255.255.255.0. Your IP should be the last valid host IP number allowed for that network.
Calculate the your IP/NETWORK configuration for eth2.
Configure eth2 as per the previous question. Confirm operations by pinging 192.168.1.23. Make sure the broadcast address is correct too.
Device eth3 is connected to a network for which your virtual machine is the gateway. The network ip is 192.168.3.48 and the netmask is 255.255.255.240. Your IP should be the last valid host IP number allowed for that network.
Calculate the your IP/NETWORK configuration for eth3.
Configure eth3 as per the previous question. Confirm operations by pinging 192.168.3.50. Make sure the broadcast address is correct too.
Using an "ip link" command, discover the mac address of eth3.
What is the mac address of 192.168.3.50? Hint: "/proc"...
If you were able to log onto 192.168.3.50, how would you have configured the default route?
How many programs are listening on ipv4 TCP sockets on your machine. Hint: the netstat command will help you here.
What is the PID of the process which is listening on UDP port 111 (sunrpc). Hint: the netstat command will help you here.
When you connected to linuxzoo.net via telnet or ssh, it was forwarded from 10.200.0.1 (the main linuxzoo server) to your machine's telnet or ssh server using a proxy. Find the port number on the 10.200.0.1 end of one of these proxy connections and enter it below. Hint: again try the netstat command very near the beginning of the output... It sometimes helps to use "-n", as this does not do DNS lookups.
In order for your virtual machine to reach the internet, it's packets travels through a number of virtual networks. The final network node is 10.200.0.1. Using traceroute, find out how many hops it takes to reach 10.200.0.1. Note you must use ICMP ECHO in traceroute, rather than the default. Find the right flag in the manual.
Use nmap to analyse the ports open on 10.200.0.1. As the nmap command can take quite a while to run, restrict your scan to the open tcp ports between port numbers 50 to 80 inclusive. List the open port numbers you find with spaces between them in the box below (e.g. if ports 50 and 60 are open, the answer is "50 60"). The numbers in your list must be sorted (smallest number first).
IMPORTANT. Linuxzoo security may shut you down if you produce too many packets too quickly! Use the following options for nmap or you may be kicked off the system. Even with these options the scan may take quite a few seconds.
nmap 10.200.0.1 -p 50-80 --max-retries 3
The tcpdump command allows us to capture all or some of the network traffic on a particular network device. In this question use the tcpdump command to capture the behaviour of a web page request emulated using lwp-request.
Capturing packets sucessfully can be tricky, especially since you have to use the same network to talk to your machine, and you dont want to capture that too... Therefore consider the following commands to perform the capturing. NOTE you only type in the characters IN BOLD.
$ tcpdump -vi eth0 port 80 > /tmp/log & [1] 3123 $ lwp-request http://linuxzoo.net ...blah...blah ...blah...blah $ kill -1 %1 [1]+ Done .... $ Where it says "eth0" you must replace that with your main network connection device, which you discovered right at the beginning of this tutorial.
Now, look at the contents of /tmp/log and enter in the box below the common IP flag which appears in most packets (The information can be found between the [..] brackets immediately after the text "flags". Ignore the information after the text "Flags" e.g. look for the one all in lowercase). Enter the two letters seen in the box below.
What is the common IP flag seen in the log: (case sensitive)
Each packet it split over multiple lines. A new packet starts on a fresh line, beginning with a timestamp. This should be folowed with IP and then the IP header information.
Assuming the packet is a TCP packet, the next link should include "Flags" (with a capital F) which are the TCP flags.
Find the packets involved with the TCP Fin flag. The first of those is the packet which first requested the stream be closed. What is the TCP sequence number of that packet?
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