# Linux Commands Every Architect/Developer Should Know **URL:** \ **Category:** Training, Tips and Tricks\ **Tags:** linux\ **Created:** [December 11, 2021, 2:13pm UTC](https://community.solace.com/t/linux-commands-every-architect-developer-should-know/1062 "2021-12-11T14:13:27Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![giri](https://yyz1.discourse-cdn.com/solace/user_avatar/community.solace.com/giri/32/877_2.png) [@giri](https://community.solace.com/u/giri)\ **Post date:** [December 11, 2021, 2:13pm UTC](https://community.solace.com/t/linux-commands-every-architect-developer-should-know/1062/1 "2021-12-11T14:13:27Z")
# Linux Commands Every Architect/Developer Should Know ## #1 – Process Monitoring - [**top**](https://man7.org/linux/man-pages/man1/top.1.html) – To view CPU & memory usage information. \_General guidance is Load Average should be similar to the number of cores for the system not under stress.\_You can also use newer version [htop](https://man7.org/linux/man-pages/man1/htop.1.html) command for more interactivity. ```auto top -u #user specific processes Press M: sort by memory, P: sort process list by CPU usage, V: Forest view, R: for reversing the order htop -u #user specific processes ``` - **[ps](https://man7.org/linux/man-pages/man1/ps.1.html)** – Classic command to view list of running processes – Linux variants have different parameter options. Below examples are the most useful: ```auto ps auwwx #list all the processes with wider format & easy to remember ps -ef | grep 'java' #to filter specific process ps -ef | awk '{print $1}' | sed '/UID/d' | sort | uniq -c | sort -nr #count running process under each user ``` - **[kill](https://man7.org/linux/man-pages/man2/kill.2.html)** – Classic command for killing a running process. **[killall](https://man7.org/linux/man-pages/man1/killall.1.html)** is useful to kill all the processes by a name. ```auto kill -l #to list all available signals kill -9 #SIGKILL signal to kill the process killall top #kill all top processes; you can put any process name ``` - **[lsof](https://man7.org/linux/man-pages/man8/lsof.8.html)**– List of Open Files by the process – very useful when debugging resources consumed by a process particularly when everything in Linux is a file. Note that it might not be installed by default in some variants (e.g. CentOS) and you need to install **“lsof”** package. ```auto lsof -u #list of files opened by a user lsof -c #list of files opened by a process named lsof -p #list of files opened by PID lsof -i #files opened by network lsof -i :443 #to find the process/service listening on a port ``` - **[fuser](https://man7.org/linux/man-pages/man1/fuser.1.html)** – shows the PIDs of processes using the specified files or file systems in Linux. You need to install **_“psmisc”_** package before using this command – see installation section below for instruction as per Linux variant. ```auto fuser 80/tcp #find the process/service listening on a particular port by running the command fuser #to find out file being used by the ``` ## #2 – File Operations - [**tail**](https://man7.org/linux/man-pages/man1/tail.1.html) – for viewing the last part of files/logs, most commonly used parameter is _“tail -f”_ - **[find](https://man7.org/linux/man-pages/man1/find.1.html)** – for searching the files. Commonly usage examples – [click here](https://www.tecmint.com/35-practical-examples-of-linux-find-command/): ```auto find . -name "*.log" #to find the log files in current directory & sub-directory find . -type f -name "*.java" #to find all java file types find . -type f -perm 0777 -print #to find files with 777 permissions find / -type f -perm 0777 -print -exec chmod 555 {} \; #to find files with 777 permissions and replace with 555 find / -size +50M -size -100M #to find files between 50-100MB size ``` - **[grep](https://man7.org/linux/man-pages/man1/grep.1.html)** – for searching pattern within file. [Click here](https://www.thegeekstuff.com/2009/03/15-practical-unix-grep-command-examples/) for different examples. ```auto grep -i "linux" *.log #case insensitive search within log files grep "REGEX" *.log #use any REGEX grep -w "word" *.log #check for full word grep -c "word" *.log #count the number of words matched grep -v "word" *.log #invert the match to display non-matching grep -r "word" *.log #to search recursively in all folders grep -A 5 -i "word" *.log #display 5 lines after the match ``` - **Others:** uniq sort diff cut ncat sed awk ## #3 – Network Monitoring - **[tcpdump](http://www.tcpdump.org/tcpdump_man.html)** – for analyzing network packet level details. Useful for packet-level inspection, detecting denial of service attacks by inspecting large packets or source, debug the source & destination generating traffic, etc.- tcpdump not port 22 and not port 25 (exclude SSH to avoid unnecessary info) _Usage examples:_ ```auto tcpdump udp #for capturing specific protocol dump; find list of protocols in /etc/protocols) tcpdump -c10 -i eth1 -n -A port 80 #dumps in ASCII format with (-A) with specific port and exit after receiving 10 packets (-c)) tcpdump -l | tee dat #Make stdout line buffered. Useful if you want to see the data while capturing it tcpdump -i eth0 host 10.122.19.222 #capture for specific IP address tcpdump -s 0 -A -vv 'tcp[((tcp[12:1] & 0xf0) >> 2):4] = 0x47455420' #capture only HTTP GET or POST only ``` 1. Note: If not installed, install “tcpdump” package (e.g. for Alpine Linux: _apk add tcpdump_). [Click here](https://www.redhat.com/sysadmin/troubleshoot-tcpdump) to read the troubleshooting article by RedHat and see 20 different examples by [clicking here](https://hackertarget.com/tcpdump-examples/). - **[netstat](https://man7.org/linux/man-pages/man8/netstat.8.html)** – Print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships - **[traceroute](https://man7.org/linux/man-pages/man8/traceroute.8.html)** – print the route packets trace to network host - **[ss](https://man7.org/linux/man-pages/man8/ss.8.html)** – utility to investigate sockets (very useful to check socket stats) - **iperf** – utility to check network bandwidth between two systems. [Click here](https://www.cyberciti.biz/faq/how-to-test-the-network-speedthroughput-between-two-linux-servers/) to read the most useful link found for iperf. - **Others:** strace, mtr, dig, sar, ifconfig (prints ip address) ## #4 – Disk & Memory Monitoring - [**du**](https://man7.org/linux/man-pages/man1/du.1.html) / [**df**](https://man7.org/linux/man-pages/man1/df.1.html) – du (disk usage of the set of FILEs, recursively for directories), df (report file system disk space usage) - **[free](https://man7.org/linux/man-pages/man1/free.1.html)** – to find out free and used memory - [**iostat**](https://man7.org/linux/man-pages/man1/iostat.1.html) – for CPU stats and I/O stats for devices & partitions - **[mount](https://man7.org/linux/man-pages/man8/mount.8.html)** – to mount a file system - **[fdisk](https://man7.org/linux/man-pages/man8/fdisk.8.html)** – to manipulate disk partition ## Installing Package Below commands are example of installing packages for different variations: ```auto $ yum install # RHEL/CentOS $ apt install # Debian/Ubuntu $ apk add # Alpine Linux $ dnf install # Fedora ``` ## Other Useful Commands - **[alias](https://ss64.com/bash/alias.html)** (for bash) – useful for creating shortcuts to frequently used commands - **[tree](https://www.howtoforge.com/linux-tree-command/)** – shows a visual representation of the files in a directory - **[watch](https://man7.org/linux/man-pages/man1/watch.1.html)** – run any command at regular intervals and displays the output - **[truncate](https://www.man7.org/linux/man-pages/man1/truncate.1.html)** – shrink or extend the size of a file to the specified size. For example, the below command will free up capacity quickly: ```auto truncate -s 0 filename ``` - **Security** : - **Top 10 commands** from bash history: ```auto cat ~/.bash_history | sort |uniq -c|sort -nr|head -n 10 ``` - [systemctl](https://man7.org/linux/man-pages/man1/systemctl.1.html)\*\*\*\*– to control the running system and other services - **Miscellaneous:** mpstat, pmap, kill, iostat, vmstat, chkconfig, uptime (shows how long system is running), pidof, cal (shows calendar), zip, unzip, ssh, whatis (locate the binary), whereis (one-line man page), finger (short dump of info about a user), w (current user info), chown (change ownership of file), chmod (change permission of files & directories), locate (to find a file), ping (to check connectivity) To conclude, these commands/utilities help not only to troubleshoot but to understand the functions of Linux operating system. Even though you are using application performance monitoring (APM) tools, as a software architect you should know these expand the full-stack knowledge. ## **Linux Useful Websites** - [Linux.org](https://www.linux.org/) – for discussion, tutorial, and references - [Linux.com](https://www.linux.com/) – by Linux Foundation for latest news, articles & updates - [Linux Foundation](https://www.linuxfoundation.org/) – community-driven site focused on Opensource - [man7.org](https://man7.org/linux/man-pages/) – Linux Online Manual - [Linux Commands Cheatsheets](https://itsfoss.com/linux-commands-cheat-sheets/) - [Explain Shell](https://explainshell.com/) – Explains each part of the command (useful when trying to understand complex commands used together with parameters) - [nixCraft/cyberciti](https://www.cyberciti.biz/) – for Linux sysadmins - [Linux Today](https://www.linuxtoday.com/) – for latest news on Linux Source: [Linux Commands Every Architect Should Know](https://vedcraft.com/learning-paths/linux-commands-every-architect-should-know/)