SystemAdmin_snippets - test - noxit/DevOps_practices

SystemAdmin_snippets
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noxit
update SystemAdmin_snippets
25 ноя 2025, 09:38
25 ноя 2025, 09:38abce26c
----------- Displays the last 10 user login 
last -n 10

----------- Display disk usage in a human-readable format
df -h | grep -E '^/dev/'

----------- Update package lists and upgrade installed packages on the system
sudo apt-get update && sudo apt-get upgrade

----------- Monitors the auth.log file in real-time for authentication failures
tail -f /var/log/auth.log | grep 'authentication failure'

----------- Finds all configuration files in /etc with server_name directive
find /etc -name '*.conf' -exec grep -H -i 'server_name' {} \;

----------- Calculates the total CPU usage percentage of all running processes
ps aux | awk '{sum+=$3}; END{print "Total CPU usage:"; print sum}'
----------- самые прожорливые процесс
ps aux --sort=-%cpu | head

----------- Shows the size of each directory in the current directory in human-readable format, sorted by size
du -hs * | sort -h

----------- Check if the proccess web server is running
ps aux | grep $PROCESS_NAME

----------- Show all listening ports on the system
netstat -tuln | grep 'LISTEN'

----------- Show size of directories in a specified path in a human-readable format
du -h --max-depth=1 /path/to/directory

----------- Show top 10 processes sorted by memory usage
ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%mem | head

----------- Backup logs older then 7 days
find / -type f -iname '*.log' -mtime +7 -exec cp {} /backup/logs \;

Reverse DNS lookup
dig -x 77.88.8.8 +short


Show routing table
route -n


Trace route and save output
traceroute -I dns.yandex.ru > traceroute_output.txt


Display network connections and their processes
ss -tulnpe		(or netstat)



Test access to multiple DNS servers
for server in 8.8.8.8 8.8.4.4 77.88.8.8; do echo "Testing DNS server: $server"; dig +short dns.yandex.ru @$server; done



Scan a range of IP addresses for open ports
for ip in $(seq 1 254); do nmap -p 80,443 192.168.1.$ip -oG - | grep open; done


Continuous monitoring of network latency
while true; do date; ping -c 5 yandex.ru  | grep icmp_seq; sleep 5; done


Ping multiple hosts simultaneously
for host in 192.168.1.1 192.168.1.2 yandex.ru; do ping -c 2 $host & done; wait

Analyze network packets and their contents with tcpdump
tcpdump -i eth0 -w capture.pcap


nmap -sn -p- 192.168.1.0/24



Perform a network speed test using a TCP connection to a remote server
iperf -c IP_Address -p Port_Number -t Time_Duration


Queries DNS information for google.com
dig yandex.ru ANY +noall +answer



Assigns the IPv4 address 192.168.1.2 with a subnet mask of 255.255.255.0 to the network interface eth0
ip addr add 192.168.1.2/24 dev eth0


Configure a network interface with a specific IP address and netmask
ifconfig eth0 192.168.1.10 netmask 255.255.255.0


Display all active network interfaces with detailed information
ip a | grep  'inet '

Check if a specific port is open on a remote host using netcat
nc -zv remote_host.com 80

проверка срзу всех основных параметров сервера
echo "=== $(date) ===" && echo "🔍 Swap usage:" && free -h && echo -e "\n📊 Memory usage per process (sorted by RAM):" && ps aux --sort=-%mem | head -11 && echo -e "\n🔄 Swap usage per process:" && (sudo smem -t -k || (echo "smem not found, install with: sudo apt install smem")) && echo -e "\n🧩 Swap devices:" && swapon --show && echo -e "\n⚙️ System load & uptime:" && uptime

Вывод размера find через du
find . -type f -name "*.log" -exec du -h {} + | sort -h