📜Script 🚨
Going into this part, you need to pay special attention to everything, as it is important to learn all that is covered here.
Do not cheat in this part! You will be asked how the script works during the evaluation, so understand it as the evaluator expects.
Architecture
For the architecture of the OS to be shown, you will use the command uname -a ("-a" == "--all"). This command prints all information, except if the CPU is unknown or the platform hardware.
Physical Cores
For the number of physical cores to be shown, we will use the file /proc/cpuinfo, which gives us information about the CPU: its type, brand, model, performance, etc. We will use grep "physical id" /proc/cpuinfo | wc -l with the grep command looking inside the file for "physical id" and with wc -l to count the lines of the grep output.
Virtual Cores
To show the number of virtual cores is very similar to the previous one. We will again use the file /proc/cpuinfo, but in this case we will use the command grep processor /proc/cpuinfo | wc -l. The usage is practically the same as before, only that instead of counting the lines of "physical id" we will do it with "processor". We do it this way for the same reason as before, the way of quantifying marks 0 if there is a processor.
RAM
To show the RAM memory we will use the command free to see at the moment information about the RAM, the used part, free, reserved for other resources, etc. For more info about the command we will put free --help. We will use free --mega since that unit of measure appears in the subject.
Disk memory
To view the occupied and available memory of the disk, we will use the df command, which stands for "disk filesystem", it is used to get a complete summary of the use of disk space. As indicated in the subject, the used memory is shown in MB, so we will then use the -m flag. Next, we will do a grep to only show us the lines that contain "/dev/" and then we will do another grep with the -v flag to exclude lines that contain "/boot". Finally, we will use the awk command and sum the value of the third word of each line to once all the lines are summed, print the final result of the sum. The entire command is as follows: df -m | grep "/dev/" | grep -v "/boot" | awk '{memory_use += $3} END {print memory_use}'.
CPU usage percentage
To view the percentage of CPU usage, we will use the vmstat command, which shows system statistics, allowing us to obtain a general detail of the processes, memory usage, CPU activity, system status, etc. We could put no option but in my case I will put an interval of seconds from 1 to 4. We will also use the tail -1 command, which will allow us to produce the output only on the last line, so of the 4 generated, only the last one will be printed. Finally, we will only print word 15, which is the available memory usage. The entire command is as follows: vmstat 1 4 | tail -1 | awk '{print $15}'. The result of this command is only part of the final result since there is still some operation to be done in the script for it to be correct. What should be done is to subtract the amount returned by our command from 100, the result of this operation will be printed with one decimal and a % at the end and the operation would be finished.
Last reboot
To see the date and time of our last restart, we will use the who command with the -b flag, as this flag will display the time of the last system boot on the screen. As has happened to us before, it shows us more information than we want, so we will filter it and only show what we are interested in, for this we will use the awk command and compare if the first word of a line is "system", the third word of that line will be printed on the screen, a space, and the fourth word. The entire command would be as follows: who -b | awk '$1 == "system" {print $3 " " $4}'.
LVM active
To check if LVM is active or not, we will use the lsblk command, which shows us information about all block devices (hard drives, SSDs, memories, etc) among all the information it provides, we can see lvm in the type of manager. For this command we will do an if because we will print Yes or No. Basically, the condition we are looking for will be to count the number of lines in which "lvm" appears and if there are more than 0 we will print Yes, if there are 0 we will print No. The entire command would be: if [ $(lsblk | grep "lvm" | wc -l) -gt 0 ]; then echo yes; else echo no; fi.
TCP connections
To check the number of established TCP connections, we will use the ss command replacing the now obsolete netstat. We will filter with the -ta flag so that only TCP connections are shown. Finally, we will do a grep to see those that are established as there are also only listening and close with wc -l to count the number of lines. The command is as follows: ss -ta | grep ESTAB | wc -l.
Number of users
We will use the users command which will show us the names of the users there are, knowing this, we will put wc -w to count the number of words in the command output. The entire command is as follows: users | wc -w.
IP adress & MAC
To obtain the host address, we will use the hostname -I command and to obtain the MAC, we will use the ip link command which is used to show or modify the network interfaces. As more than one interface, IP's etc. appear, we will use the grep command to search for what we want and thus be able to print only what is requested. To do this, we will put ip link | grep "link/ether" | awk '{print $2}' and in this way we will only print the MAC.
Number of commands executed with sudo
To obtain the number of commands executed with sudo, we will use the journaclctl command, which is a tool that is responsible for collecting and managing the system logs. Next, we will put _COMM=sudo in order to filter the entries by specifying its path. In our case we put _COMM because it refers to an executable script. Once we have filtered the search and only the sudo logs appear, we still need to filter a bit more as when you start or close the root session it also appears in the log, so to finish filtering we will put a grep COMMAND and this will only show the command lines. Finally, we will put wc -l so that the lines are numbered. The entire command is as follows: journalctl _COMM=sudo | grep COMMAND | wc -l). To check that it works correctly, we can run the command in the terminal, put a command that includes sudo and run the command again and it should increase the number of sudo executions.
Total result of the script
⚠️ Remember not to copy and paste if you do not know the function of each command. ⚠️
#!/bin/bash
# ARCH
arch=$(uname -a)
# CPU PHYSICAL
cpuf=$(grep "physical id" /proc/cpuinfo | wc -l)
# CPU VIRTUAL
cpuv=$(grep "processor" /proc/cpuinfo | wc -l)
# RAM
ram_total=$(free --mega | awk '$1 == "Mem:" {print $2}')
ram_use=$(free --mega | awk '$1 == "Mem:" {print $3}')
ram_percent=$(free --mega | awk '$1 == "Mem:" {printf("%.2f"), $3/$2*100}')
# DISK
disk_total=$(df -m | grep "/dev/" | grep -v "/boot" | awk '{disk_t += $2} END {printf ("%.1fGb\n"), disk_t/1024}')
disk_use=$(df -m | grep "/dev/" | grep -v "/boot" | awk '{disk_u += $3} END {print disk_u}')
disk_percent=$(df -m | grep "/dev/" | grep -v "/boot" | awk '{disk_u += $3} {disk_t+= $2} END {printf("%d"), disk_u/disk_t*100}')
# CPU LOAD
cpul=$(vmstat 1 2 | tail -1 | awk '{printf $15}')
cpu_op=$(expr 100 - $cpul)
cpu_fin=$(printf "%.1f" $cpu_op)
# LAST BOOT
lb=$(who -b | awk '$1 == "system" {print $3 " " $4}')
# LVM USE
lvmu=$(if [ $(lsblk | grep "lvm" | wc -l) -gt 0 ]; then echo yes; else echo no; fi)
# TCP CONNEXIONS
tcpc=$(ss -ta | grep ESTAB | wc -l)
# USER LOG
ulog=$(users | wc -w)
# NETWORK
ip=$(hostname -I)
mac=$(ip link | grep "link/ether" | awk '{print $2}')
# SUDO
cmnd=$(journalctl _COMM=sudo | grep COMMAND | wc -l)
wall " Architecture: $arch
CPU physical: $cpuf
vCPU: $cpuv
Memory Usage: $ram_use/${ram_total}MB ($ram_percent%)
Disk Usage: $disk_use/${disk_total} ($disk_percent%)
CPU load: $cpu_fin%
Last boot: $lb
LVM use: $lvmu
Connections TCP: $tcpc ESTABLISHED
User log: $ulog
Network: IP $ip ($mac)
Sudo: $cmnd cmd"Result after executing the script ↙️
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