Commands used for System Information

Command Name & Description	Command(s)	Sample Output
DATE The simple “date” command displays the current date and time (including the day of the week, month, time, time zone, year). Date TZ By default, “date” command uses the time zone defined in path “/etc/localtime”. Linux user can change the time zone via Terminal by using command “TZ”. Date --set Linux allows its user to set the current date and time of the system manually. Syntax: date –set=”Date_in_format(YYMMDD) Time_in_format(HH:MM)” Date -d To operate the system on a specific date, you can change the date by using “-d”. Syntax: date -d Date_to_operate_system_on	`date` `TZ=GMT date TZ=America/New_York date` `sudo date --set="20230519 22:10"` `date -d now date -d yesterday date -d tomorrow date -d last-Sunday date -d "1997-04-22"`	`$ date Thu Mar 2 07:23:38 PM EST 2023` `$ TZ=GMT date Fri Mar 3 12:03:59 AM GMT 2023 $ TZ=America/New_York date Thu Mar 2 07:04:12 PM EST 2023` `$ date -d now Thu Mar 2 07:36:55 PM EST 2023 $ date -d yesterday Wed Mar 1 07:37:00 PM EST 2023`
DF The command “df” shows the amount of disk space used and disk space available on every file system containing each filesystem’s name and its path. Syntax: df The command “df -h” shows the same result as the command “df” but now the data is in a more human-readable form that can be easily comprehended by a new user. Syntax: df -h	`df df -h`	$ df Filesystem 1K-blocks Used Available Use% Mounted on tmpfs 1623284 3612 1619672 1% /run /dev/nvme0n1p3 491343600 18123184 452739188 4% / tmpfs 8116400 104604 8011796 2% /dev/shm tmpfs 5120 4 5116 1% /run/lock tmpfs 8116400 0 8116400 0% /run/qemu /dev/nvme0n1p2 456036 182424 239424 44% /boot /dev/nvme0n1p1 98304 57271 41033 59% /boot/efi /dev/sda1 47744748 57156 45229840 1% /tmp /dev/sda3 2787016696 1123163768 1531975216 43% /home /dev/sda2 47745772 31301948 13986020 70% /var 192.168.1.1:/media/TR-004 11627352064 9633692672 1407599616 88% /media/tim/TR-004 192.168.1.1:/ubuntu-data 959776768 657463296 253486080 73% /media/tim/ubuntu01-data 192.168.1.11:/home/tim 479593984 21986816 433171968 5% /media/hass-srv tmpfs 1623280 288 1622992 1% /run/user/1000 $ df -h Filesystem Size Used Avail Use% Mounted on tmpfs 1.6G 3.6M 1.6G 1% /run /dev/nvme0n1p3 469G 18G 432G 4% / tmpfs 7.8G 103M 7.7G 2% /dev/shm tmpfs 5.0M 4.0K 5.0M 1% /run/lock tmpfs 7.8G 0 7.8G 0% /run/qemu /dev/nvme0n1p2 446M 179M 234M 44% /boot /dev/nvme0n1p1 96M 56M 41M 59% /boot/efi /dev/sda1 46G 56M 44G 1% /tmp /dev/sda3 2.6T 1.1T 1.5T 43% /home /dev/sda2 46G 30G 14G 70% /var 192.168.1.1:/media/TR-004 11T 9.0T 1.4T 88% /media/tim/TR-004 192.168.1.1:/ubuntu-data 916G 628G 242G 73% /media/tim/ubuntu01-data 192.168.1.11:/home/tim 458G 21G 414G 5% /media/hass-srv tmpfs 1.6G 288K 1.6G 1% /run/user/1000
FREE The command “free” displays the amount of free and used memory in the complete system. Syntax: free	`free`	`$ free total used free shared buff/cache available Mem: 16232804 10545772 978552 125388 4708480 5252532 Swap: 2097152 2090408 6744`
PS The command “ps” which is also known as the process status command is used to provide information about the processes currently running on the system, including their respective process identification numbers (PIDs). Syntax: ps PS AUX & PS -EF Both list all processes of all users. In that aspect `-e` and `ax` are completely equivalent. Where they differ is output format specifier, `-f` is "full", while `u` is "user-oriented". The displayed columns are different: columns for `ps -f` `UID PID PPID C STIME TTY TIME CMD` columns for `ps u` `USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND`	`ps ps -ef ps -aux`	$ ps PID TTY TIME CMD 434765 pts/0 00:00:00 bash 441698 pts/0 00:00:00 ps $ ps -ef UID PID PPID C STIME TTY TIME CMD root 1 0 0 Feb07 ? 00:19:03 /sbin/init splash root 2 0 0 Feb07 ? 00:00:03 [kthreadd] root 3 2 0 Feb07 ? 00:00:00 [rcu_gp] root 4 2 0 Feb07 ? 00:00:00 [rcu_par_gp] root 5 2 0 Feb07 ? 00:00:00 [slub_flushwq] root 6 2 0 Feb07 ? 00:00:00 [netns] $ ps -aux USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1 0.0 0.0 169808 12472 ? Ss Feb07 19:03 /sbin/init splash root 2 0.0 0.0 0 0 ? S Feb07 0:03 [kthreadd] root 3 0.0 0.0 0 0 ? I< Feb07 0:00 [rcu_gp] root 4 0.0 0.0 0 0 ? I< Feb07 0:00 [rcu_par_gp] root 5 0.0 0.0 0 0 ? I< Feb07 0:00 [slub_flushwq] root 6 0.0 0.0 0 0 ? I< Feb07 0:00 [netns]
UPTIME The command “uptime” provides information about how long the system has been running in one line. The result for this command includes the current time, the time duration system has been running, the number of users who are currently logged on, and the system load averages for the past 1, 5, and 15 minutes respectively. Syntax: uptime	`uptime`	`$ uptime 19:59:06 up 22 days, 20:17, 1 user, load average: 0.52, 0.39, 0.38`
W The command “w” displays detailed information about the users who are logged into the system currently. Syntax: w	`w`	`$ w 20:00:25 up 22 days, 20:18, 1 user, load average: 0.44, 0.41, 0.38 USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT tim :1 :1 07Feb23 ?xdm? 2days 0.00s /usr/libexec/gdm-x-session --run-script env`
PASSWD The command “passwd” stands for password and it is used to change the password of the user. Syntax: passwd user_name	`passwd my_user`	`$ passwd tim changing password for tim. (current) UNIX password: Enter new UNIX password: Retype new UNIX password: passwd: password updated successfully`
EXIT The command “exit” as the name says it is used to exit from the system and log out from the current user. Syntax: exit	`exit`	`$ exit logout Connection to 192.168.1.1 closed.`
SHUTDOWN The command “shutdown” is used to shut down the system. Syntax: shutdown	`shutdown`	`$ shutdown Shutdown scheduled for Thu 2023-03-02 20:12:13 EST, use 'shutdown -c' to cancel.`

Commands used for File Handling

LS The command “ls” displays the list of all directories, folder, and files present in the current directory. LS - LTR The above-mentioned command displays the name of directories, folders, files with their respective owner name, group’s name, and rights your user has over these. MKDIR The command “mkdir” allows users to create directories/folders in the system. The user running this command must have suitable rights over the parent directory to create a directory or they will receive an error. Syntax: mkdir New_Directory’s_Name RMDIR The command “rmdir” allows users to remove directories/folders from the system. The user running this command must have suitable rights over the parent directory to remove a directory AND the directory must not have any files or sub-directories within it or you will receive an error. Syntax: rmdir Directory’s_Name RM The command “rm” is used to remove files from a directory. RM -RF Permanently deletes the specified directory and ALL files and sub-directories beneath the specified directory. Be VERY careful using this command as you can inadvertantly delete your whole drive!	`ls ls -ltr` `mkdir NewDirectory` `rmdir DirectoryName` `rm filename` `rm -rf /path/to/dir/name`	`~/docs$ ls docs2 doc.txt ~/docs$ cd .. ~$ rmdir docs rmdir: failed to remove 'docs': Directory not empty ~$ rm -rf /home/tim/docs/ ~$` `~$ ls -ltr total 124080 -rwxrwxr-x 1 tim tim 11384 Feb 10 2014 bin_steamdeps.py -rw-rw-r-- 1 tim tim 31223808 Mar 26 2018 R8000-back-to-ofw.trx drwxr-xr-x 2 tim tim 4096 Sep 3 2018 Templates drwxr-xr-x 2 tim tim 4096 Sep 3 2018 Public` `mkdir docs rmdir docs rm doc.txt rm doc.* rm -rf /home/tim/docs/`
TOUCH Creates an empty file at the specified path with the specified name. Useful for creating a blank file you intend to edit with a CLI editor, such as VIM or NANO.	`touch /path/name/filename.ext`	`~$ ls doc.txt ls: cannot access 'doc.txt': No such file or directory ~$ touch /home/tim/doc.txt ~$ ls doc.txt doc.txt`