What are the Linux system management commands and parameters?

-c Modify the remark text of the user account.
　-d login directory> Modify the directory when the user logs in.
　-e Modify the validity period of the account.
　-f Modify the number of days after the password expires before the account will be closed.
　-g Modify the groups to which the user belongs.
　-g Modify the additional groups to which the user belongs.
　-l Modify the user account name.
　-l 　Lock the user password and make the password invalid.
　-s Modify the shell used by the user after logging in.
　-u Modify user id.
　-u Unlock the password.

userdel

Function description: Delete user account.

Syntax: userdel [-r][user account]

Supplementary instructions: userdel can delete user accounts and related files. If no parameters are added, only the user account will be deleted, but the related files will not be deleted.

Parameters:
-f Delete the user login directory and all files in the directory.

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userconf

Function description: User account setting program.

Syntax: userconf [--addgroup ][--adduser ][--delgroup ][--deluser ][--help]

Supplementary explanation: userconf is actually a symbolic link to linuxconf, providing a graphical interface for administrators to create and manage various Class account. If no parameters are added, the graphical interface will be entered.

Parameters:
--addgroup Add a new group.
　--adduser Add a new user account.
　--delgroup Delete the group.
　--deluser Delete user account.
　--help Display help.

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useradd

Function description: Create a user account.

Syntax: useradd [-mmnr][-c ][-d ][-e ][-f ][-g ][-s ][-u ][user account] or useradd -d [-b][-e ][-g ][-g ][-s ]

Supplementary note: useradd can be used to create users account number. After the account is created, use passwd to set the password for the account. You can use userdel to delete the account. The account created using the useradd command is actually saved in the /etc/passwd text file.

Parameters:
-c Add remark text. The remark text will be saved in the remark field of passwd.　
　-d Specifies the starting directory when the user logs in.
　-d Change the default value.
　-e Specify the validity period of the account.
　-f Specifies the number of days after the password expires to close the account.
　-g Specifies the group to which the user belongs.
　-g Specify additional groups to which the user belongs.
　-m 　Automatically create the user's login directory.
-m Do not automatically create the user's login directory.
　-n Cancel the creation of a group named by the user name.
　-r Establish a system account.
　-s　Specify the shell used by the user after logging in.
　-u 　Specifies the user id.

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uname

Function description: Display system information.

Syntax: uname [-amnrsv][--help][--version]

Supplementary instructions: uname can display information about the computer and operating system.

Parameters:
-a or --all Display all information.
　-m or --machine Display the computer type.
　-n or -nodename The host name displayed on the network.
　-r or --release Display the release number of the operating system.
　-s or --sysname Display the operating system name.
　-v 　　Displays the version of the operating system.
　--help Display help.
　--version Display version information.

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top

Function description: Display and manage executing programs.

Syntax: top [bciqss][d ][n ]

Supplementary instructions: Executing the top command can display that it is currently being executed in the system program and manage it with hotkeys through the interactive interface it provides.

Parameters:
b Use batch mode.
　c When listing programs, display the complete instructions of each program, including instruction name, path, parameters and other related information.
　d Set the interval time for the execution status of the top monitoring program, in seconds.
i When executing the top command, programs that are idle or have become zombies are ignored.
　n Set the number of times the monitoring information is updated.
　q Continuously monitor the status of program execution.
　s Use confidentiality mode to eliminate potential crises in interactive mode.
　s Use accumulation mode, its effect is similar to the -s parameter of the ps command.

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tload

Function description: Display system load status.

Syntax: tload [-v][-d ][-s ][Terminal number]

Supplementary instructions: tload command Simply display system load status in text mode using ascii characters. If the terminal number is not given, the load status will be displayed on the terminal that executes the tload command.

Parameters:
-d Set the interval time for tload to detect system load, in seconds.
　-s Set the vertical scale size of the chart, in columns.
　-v 　Display version information.

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swatch(simple watcher)

Function description: System monitoring program.

Syntax: swatch [-a ][-c ][-f ][-i ][ -p ][-r ][-t ]

Supplementary note: swatch can be used to monitor system record files and detect specific When an event occurs, perform the specified action. The events monitored by swatch and the actions corresponding to the events are stored in the swatch configuration file. The default configuration file is .swatchrc in the support root directory. However, there is no .swatchrc configuration file in the default user root directory of red hat linux. You can copy the /usr/doc/swatch-2.2/config_files/swatchrc.personal file to the .swatchrc in the user root directory, and then modify it. The events and actions to be monitored by swatchrc.

Parameters:
-a In the default configuration file, the delimiting character of the action is comma by default.
　-c Settings File> Specify the configuration file instead of using the default configuration file.
　-f record file> Check the specified record file. After the check is completed, the record file will not continue to be monitored.
　-i delimiter character> Specifies the delimiter character of the input record, the default is the newline character.
　-p delimiter character> Specifies the delimiter character of events in the configuration file. The default is comma.
　-r time> Restart at the specified time.
　-t Checks the specified log file, and monitors subsequent records added to the log file.

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suspend

Function description: Suspend the execution of the shell.

Syntax: suspend [-f]

Supplementary explanation: suspend is a built-in command of the shell, which can suspend the currently executing shell. To recover, sigcont information must be used.

Parameters:
-f If the currently executing shell is the login shell, suspend cannot suspend this shell by default. To force the login shell to be suspended, the -f parameter must be used.

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sudo

Function description: Execute instructions as another identity.

Syntax: sudo [-bhhpv][-s ][-u ][command] or sudo [-klv]

Supplementary explanation: sudo allows users to use other commands The identity to execute the specified instructions, the default identity is root. The user who can execute sudo commands is set in /etc/sudoers. If an unauthorized user attempts to use sudo, a warning email will be sent to the administrator. When using sudo, the user must first enter the password, and then there is a validity period of 5 minutes. After the period, the password must be re-entered.
Parameters:
-b Execute instructions in the background.
　-h 　Display help.
-h Set the home environment variable to the home environment variable of the new identity.
-k Ends the validity period of the password, that is, you need to enter the password the next time you execute sudo.
　-l List the commands that the current user can and cannot execute.
　-p Change the prompt symbol for asking for password.
　-s Execute the specified shell.
　-u Use the specified user as the new identity. If this parameter is not added, root will be used as the new identity by default.
-v Extend the password validity period by 5 minutes.
　-v 　Display version information.

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su(super user)

Function description: Change user identity.

Syntax: su [-flmp][--help][--version][-][-c ][-s ][user account]

Supplement Description: su allows users to temporarily change their login identity. When changing, you must enter the user account and password you want to change.

Parameters:
-c or --command= After executing the specified command, the original identity will be restored.
-f or --fast is suitable for csh and tsch, so that the shell does not need to read the startup file.
　-.-l or --login When changing the identity, the working directory, home, shell, user, and logname will also be changed at the same time. In addition, the path variable will also be changed.
　-m,-p or --preserve-environment When changing the identity, do not change the environment variables.
　-s or --shell= Specifies the shell to be executed.
　--help Display help.
　--version Display version information.
　[User Account] Specify the user to be changed. If this parameter is not specified, the default is changed to root.

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sliplogin

Function description: Add the slip interface to the standard input.

Syntax: sliplogin [user name]

Supplementary explanation: sliplogin can add the slip interface to the standard input and turn the general terminal connection into a slip connection. It is usually used to create a slip server and allow remote computers to connect to the server through slip. sliplogin goes to check if there is the same user name in the /etc/slip/slip.hosts file. After passing the check, sliplogin will call and execute the shell script to set the IP address, subnet mask and other network interface environment. This shell script is usually /etc/slip/slip.login.

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shutdown

Function description: System shutdown command.

Syntax: shutdown [-effhknr][-t seconds][time][warning message]

Supplementary instructions: The shutdown command can close all programs and restart them according to the user's needs. The action of powering on or off.

Parameters:
-c When executing the shutdown -h 11:50 command, just press the key to interrupt the shutdown command.
　-f 　Do not execute fsck when restarting.
　-f 　Execute fsck when restarting.
-h Shut down the system.
　-k Just sends information to all users, but will not actually shut down the computer.
-n does not call the init program for shutdown, but shutdown itself.
　-r 　Restart after shutdown.
　-t How many seconds to delay between sending a warning message and deleting the message.
[Time] Set the time after which the shutdown command will be executed.
　[Warning message] Message to be sent to all logged in users.

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screen

Function description: Multi-window management program.

Syntax: screen [-amrvx -ls -wipe][-d ][-h ][-r ][-s ][-s ]

Supplementary explanation: screen is a multi-window management program. The so-called window here refers to a full-screen text mode screen. Usually it is only possible to use the screen program when logging into the host using telnet or using an old-fashioned terminal.

Parameters:
-a Adjust all windows to the size of the current terminal.
　-d Take the specified screen job offline.
　-h Specifies the number of buffer lines in the window.
　-m Even if the screen job is currently in operation, a new screen job is still forced to be created.
　-r Resumes the offline screen job.
　-r Try to resume offline jobs first. If no offline job is found, a new screen job is created.
　-s Specifies the shell to be executed when creating a new window.
　-s Specifies the name of the screen job.
　-v 　Display version information.
　-x 　Resume the previous offline screen job.
　-ls or --list Display all current screen jobs.
-wipe Check all current screen jobs and delete screen jobs that are no longer available.

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rwho

Function description: View system users.

Syntax: rwho [-a]

Supplementary explanation: The effect of the rwho command is similar to the who command, but it will display the users of all hosts in the LAN. The host must provide the rwhod resident service function before the rwho command can be used.

Parameters:
-a List all users, including users who have been idle for more than 1 hour.

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　rsh(remote shell)

Function description: Remote login shell.

Syntax: rsh [-dn][-l ][host name or ip address][execution command]

Supplementary explanation: rsh provides a user environment, that is shell so that commands can be executed on the specified remote host.

Parameters:
-d Use the socket-level debugging function.
　-l Specify the user name to log in to the remote host.
　-n Directs the entered command number to the special peripheral device codenamed /dev/null.

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　rlogin(remote login)

Function description: remote login.
Syntax: rlogin [-8el][-e ][-l ][Host name or IP address]

Supplementary instructions: Execute the rlogin command to open Terminal stage operation and log in to the remote host.

Parameters:
-8 Allows input of 8-bit character data.
　-e escape character> Set the escape character.
　-e Filter out escape characters.
　-lUsername> Specify the user name to log in to the remote host.
-l Use litout mode for remote login phase operations.

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renice

Function description: Adjust priority.

Syntax: renice [priority][-g ...][-p ...][-u

Supplementary explanation: The renice command can re-adjust the priority level of program execution. The default is to specify a program with a program ID to adjust its priority. You can also specify a program group or user name to adjust the priority level, and modify the priorities of all programs belonging to the program group or user. The level ranges from -20--19. Only the system administrator can change the priority of other user programs, and only the system administrator can set negative levels.
Parameters:
-g Use the program group name to modify the priorities of all programs belonging to the program group.
　-p Change the priority level of the program. This parameter is the default value.
　-u Specify the user name and modify the priorities of all programs belonging to this user.

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reboot

Function description: Reboot.

Syntax: dreboot [-dfinw]

Supplementary instructions: Executing the reboot command can stop the system and restart it.

Parameters:
-d Do not write data to the log file /var/tmp/wtmp when restarting. This parameter has the effect of the -n parameter.
　-f 　Forced restart without calling the shutdown command function.
-i Close all network interfaces before restarting.
　-n 　Do not check whether there are unfinished programs before restarting.
-w Only for testing, it does not actually restart the system. It will only write the restart data to the wtmp record file in the /var/log directory.

pstree(process status tree)

Function description: Display the program in a tree view.

Syntax: pstree [-acghlnpuuv][-h ][/]

Supplementary instructions: pstree The instructions use ASCII characters to display the tree structure and clearly express the interrelationship between programs. If you do not specify a program identification code or user name, the first program when the system is started will be regarded as the base layer, and all subsequent programs will be displayed. If a user name is specified, the first program belonging to the user will be used as the base layer, and then all programs of the user will be displayed.

Parameters:
-a Displays the complete instructions of each program, including path, parameters or identification of resident services.
　-c 　　Do not use condensed notation.
-g Use the column drawing characters of the vt100 terminal.
　-h When listing the tree diagram, specifically indicate the currently executing program.
　-h The effect of this parameter is similar to that of specifying the -h parameter, but it specifically identifies the specified program.
　-l Display the tree diagram in long column format.
　-n Sort by program identification code. The default is to sort by program name.
　-p Display program identification code.
　-u 　Display user name.
-u Use utf-8 column drawing characters.
　-v 　Display version information.

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ps(process status)

Function description: Report program status.

Syntax: ps [-aacdefhjlmnvwy][acefghlnrsstuvxx][-c ][-g ][-g ][-p < ;Program identification code>][p ][-s ][-t ][t ][- u ][-u ][u ][-][--cols ][--cumulative][--deselect][--forest][--headers][--help][-- info][--lines < ;Show number of columns>][--no-headers][--group ][-group ][--pid ] [--rows ][--sid ][--tty ][--user ][--user ][--version][--width ]

Supplementary explanation: ps is a command used to report the execution status of the program. You can use it with kill Instructions are interrupted at any time and unnecessary programs are deleted.

Parameters:
-a Displays all programs executed under the terminal, except the stage job leader.
　a Displays all programs under the current terminal, including programs of other users.
　-a Display all programs.
　-c Display cls and pri fields.
　c When listing programs, display the real instruction name of each program without including paths, parameters or identification of resident services.
　-c Specifies the name of the execution instruction and lists the status of the program that executes the instruction.
-d Displays all programs except the program of the stage job leader.
　-e The effect of this parameter is the same as specifying the a parameter.
　e When listing programs, display the environment variables used by each program.
-f Display uid, ppip, c and stime fields.
　f Use ASCII characters to display the tree structure and express the relationship between programs.
　-g This parameter has the same effect as specifying the -g parameter. It can also be specified by the name of the stage job leader.
　g Displays all programs under the current terminal, including the group leader's programs.
　-g Lists the status of programs belonging to this group. It can also be specified using the group name.
h Does not display the title bar.
　-h Displays a tree structure, indicating the relationship between programs.
　-j or j Use job control format to display program status.
　-l or l Use detailed format to display program status.
　l List the relevant information of the field.
　-m or m Display all execution threads.
　n Use numbers to represent the user and wchan fields.
-n Displays all programs, except programs under the terminal that execute the ps command.
　-p Specifies the program identification code and lists the status of the program.
　p The effect of this parameter is the same as that of specifying the -p parameter, with only slight differences in the list format.
　r Only the programs currently being executed by the current terminal are listed.
　-s Specifies the program identification code of the stage operation and lists the status of the programs belonging to this stage operation.
　s Use the program signal format to display the program status.
　s When listing programs, include interrupted subroutine information.
　-t Specifies the terminal number and lists the status of the programs belonging to the terminal.
　t The effect of this parameter is the same as that of specifying the -t parameter, with only slight differences in the list format.
　-t Display all programs under the current terminal.
　-u This parameter has the same effect as specifying the -u parameter.
　u Display program status in user-oriented format.
　-u Lists the status of programs belonging to this user, which can also be specified using the user name.
　u Lists the status of programs belonging to this user.
　v Use virtual memory format to display program status.
　-v or v Display version information.
　-w or w Use a wide format to display program status.
x Display all programs, not distinguished by terminal.
　x Use the old linux i386 login format to display program status.
　-y When used with the parameter -l, the f (flag) field will not be displayed, and the addr field will be replaced by the rss field.
　- The effect of this parameter is the same as specifying the p parameter.
　--cols Set the maximum number of characters per column.
　--columns This parameter has the same effect as specifying the --cols parameter.
　--cumulative The effect of this parameter is the same as the specified s parameter.
　--deselect The effect of this parameter is the same as specifying the -n parameter.
　--forest The effect of this parameter is the same as specifying the f parameter.
　--headers Repeatedly display the header column.
　--help 　Online help.
　--info Display troubleshooting information.
　--lines Set the number of columns in the display screen.
　--no-headers The effect of this parameter is the same as that of specifying the h parameter, with only slight differences in the list format.
　--group This parameter has the same effect as specifying the -g parameter.
　--group This parameter has the same effect as specifying the -g parameter.
　--pid The effect of this parameter is the same as specifying the -p parameter.
　--rows This parameter has the same effect as specifying the --lines parameter.
　--sid The effect of this parameter is the same as specifying the -s parameter.
　--tty This parameter has the same effect as specifying the -t parameter.
　--user The effect of this parameter is the same as specifying the -u parameter.
　--user The effect of this parameter is the same as specifying the -u parameter.
--version The effect of this parameter is the same as specifying the -v parameter.
　--widty This parameter has the same effect as specifying the -cols parameter.

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procinfo(process information)

Function description: Display system status.

Syntax: procinfo [-abddfhimssv][-f

][-n ]

Supplementary instructions: The procinfo command is obtained from the /proc directory Read the relevant data, properly organize the data and output it to the standard output device.

Parameters:
-a Display all information.
-b Displays the number of blocks in the disk device, not the number of accesses.
-d Displays the difference in system information changes per second, rather than the total value. This parameter must be used in conjunction with the -f parameter
　-d The effect of this parameter is similar to that of specifying the -d parameter, but the information in the memory and swap file is the total value.
-f Enter the full-screen interactive operation interface.
　-f

Output the information status to a file instead of the default standard output device.
　-h 　Online help.
　-i Display the complete irp list.
　-m 　Displays related information such as system modules and peripheral devices.
　-nInterval seconds> Set the information update speed of full-screen interactive mode, in seconds.
-s Displays system memory, disk space, irp and dma information. This is the default value.
　-s When used with the parameter -d or -d, the information will be updated every second, regardless of whether the parameter -n is used.
　-v 　Display version information.

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nice

Function description: Set priority.

Syntax: nice [-n ][--help][--version][Execution command]

Supplementary explanation: The nice command can change the priority of program execution power level.

Parameters: -n or - or --adjustment= Set the priority level of the command to be executed. The level ranges from -20 to 19, with -20 being the highest and 19 being the lowest. Only the system administrator can set negative levels.
　--help 　Online help.
　--version Display version information.

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newgrp

Function description: Log in to another group.

Syntax: newgrp [group name]

Additional explanation: The newgrp command is similar to the login command, when it is to log in to the system again with the same account and another group name. To use the newgrp command to switch groups, you must be a user of the group, otherwise you will not be able to log in to the specified group. If a single user wants to belong to multiple groups at the same time, he needs to use the alternate user setting. If no group name is specified, the newgrp command will log in to the default group of the user name.

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logrotate

Function description: Manage log files.

Syntax: logrotate [-?dfv][-s ][--usage][configuration file]

Supplementary instructions: Use the logrotate command to make it easy for you Record files generated by the management system. It provides automatic replacement, compression, deletion and mailing of log files. Each log file can be set to be processed daily, weekly or monthly, and can also be processed immediately when the file is too large. You must edit it yourself and specify the configuration file. The default configuration file is stored in the /etc directory and the file name is logrotate.conf.

Parameters:
-? or --help Online help.
　-d or --debug Display the instruction execution process in detail to facilitate troubleshooting or understanding the program execution status.
　-f or --force Forcibly start the log file maintenance operation, even if the logrotate command deems it not necessary.
　-s or --state= Use the specified state file.
　-v or --version Display the instruction execution process.
　-usage Display the basic usage of the command.

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logout

Function description: Exit the system.

Syntax: logout

Supplementary explanation: The logout command allows the user to log out of the system, and its functions correspond to the login command.

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logname

Function description: Display user name.

Syntax: logname [--help][--version]

Supplementary instructions: Execute the logname command, it will display the name of the current user.

Parameters:
--help Online help.
　--vesion Display version information.

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login

Function description: Log in to the system.

Syntax: login

Supplementary explanation: The login command allows users to log in to the system, and you can also use its function to change the login identity at any time. In the slackware distribution, you can append the user name you want to log in to the command, and it will directly ask for the password and wait for the user to enter. When the /etc directory contains a file named nologin, only the root account can log in to the system, and other users are not allowed to log in.

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lastb

Function description: List information about users who failed to log in to the system.

Syntax: lastb [-adrx][-f ][-n ][account name...][terminal number...]

Supplementary instructions: Execute the lastb command alone, it will read the file named btmp located in the /var/log directory, and display the list of users who failed to log in
recorded in the file. .

Parameters:
-a Display the host name or IP address from where you log in to the system on the last line.
-d Convert ip address to host name.
　-f Specifies the log file.
　-n or - Set the number of display columns for the list.
　-r Does not display the host name or IP address used to log in to the system.
　-x 　Displays system shutdown, restart, and execution level changes and other information.

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last

Function description: List information related to users who have logged in to the system currently and in the past.

Syntax: last [-adrx][-f ][-n ][account name...][terminal number...]

Supplementary instructions: Execute the last command alone, it will read the file named wtmp located in the /var/log directory, and display the list of all users logged into the system recorded in the file.

Parameters:
-a Display the host name or IP address from where you log in to the system on the last line.
-d Convert ip address to host name.
　-f Specifies the log file.
　-n or - Set the number of display columns for the list.
　-r Does not display the host name or IP address used to log in to the system.
　-x 　Displays system shutdown, restart, and execution level changes and other information.

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kill

Function description: Delete the executing program or job.

Syntax: kill [-s ][program] or kill [-l ]

Supplementary instructions: kill can change the specified Information is sent to the program. The default message is sigterm(15), which can terminate the specified program. If the program still cannot be terminated, you can use the sigkill(9) message to try to forcefully delete the program. The program or job number can be viewed using the ps command or jobs command.
Parameters:
-l If the option is not added, the -l parameter will list all message names.
　-s Specifies the message to be sent.
　[Program] [Program] can be the pid or pgid of the program, or the job number.

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id

Function description: Display the user's id and the id of the group to which it belongs.

Syntax: id [-ggnru][--help][--version][user name]

Supplementary explanation: id will display the actual and effective id of the user and the group to which it belongs. If the two ids are the same, only the actual id is displayed. If only the user name is specified, the current user's ID will be displayed.

Parameters:
-g or --group Display the id of the group to which the user belongs.
　-g or --groups Display the ids of additional groups to which the user belongs.
　-n or --name Display the name of the user, group or additional group.
　-r or --real Display the actual id.
　-u or --user Display user id.
　-help 　Display help.
　-version Display version information.

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halt

Function description: Shut down the system.

Syntax: halt [-dfinpw]

Supplementary explanation: halt will first detect the runlevel of the system. If runlevel is 0 or 6, shut down the system, otherwise call shutdown to shut down the system.

Parameters:
-d Do not record in wtmp.
-f Regardless of the current runlevel, the system is forced to shut down without calling shutdown.
-i Before halting, close all network interfaces.
　-n 　There is no need to execute sync first before halting.
　-p 　After halt, execute poweroff.
-w Only records in wtmp without actually ending the system.

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groupmod(group modify)

Function description: Change the group identification code or name.

Syntax: groupmod [-g <-o>][-n ][Group name]

Supplement Note: When you need to change the identification code or name of a group, you can use the groupmod command to complete the work.

Parameters:
-g Set the group ID to be used.
　-o 　Reuse group ID.
　-n Set the group name to be used.

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groupdel(group delete)

Function description: Delete the group.

Syntax: groupdel [group name]

Supplementary instructions: When you need to delete a group from the system, you can use the groupdel command to complete this task. If the group still contains some users, they must be deleted before the group can be deleted.

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gitps(gnu interactive tools process status)

Function description: Report program status.

Syntax: gitps [acefgjlnrsstuvwxx][p ][t ][u ]

Supplementary instructions: gitps is a command used to report and manage program execution. Basically, it reports and manages programs through the ps command. It can also interrupt at any time and delete unnecessary programs through the gitps command. Because the gitps command will execute the ps command, its parameters are quite similar to the ps command.

Parameters:
a Display all programs under the current terminal, including other users’ programs.
　c When listing programs, display the real command name of each program, without including the path, parameters or identification of resident services.
　e When listing programs, display the environment variables used by each program.
　f Use ASCII characters to display the tree structure and express the relationship between programs.
　g Displays all programs under the current terminal, including the group leader's programs.
　j Use the work control format to display the program status.
　l Use a slim format to display program status.
　n Use numbers to represent the user and wchan fields.
　p Specify the program identification code and list the status of the program.
　r Only the programs currently being executed by the current terminal are listed.
　s Use the program signal format to display the program status.
　s When listing programs, include interrupted subroutine information.
　t Specify the terminal number and list the status of the programs belonging to the terminal.
　t Display all programs under the current terminal.
　u Display program status in user-oriented format.
　u Lists the status of programs belonging to this user.
　v Use virtual memory format to display program status.
　w Use a broad format to display program status.
　x Display all programs, not distinguished by terminal.
　x Use the old linux i386 login format to display the program status.

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fwhois

Function description: Find and display user information.

Syntax: fwhios [account name]

Supplementary explanation: The function of this command is somewhat similar to the finger command. It will find and display user-related information for the specified account. The difference is that the fwhois command searches the whois database of network solutions. The account name must be registered on it to find it, and there is no difference in case of the name.

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free

Function description: Display memory status.

Syntax: free [-bkmotv][-s ]

Supplementary explanation: The free command will display memory usage, including physical memory and virtual swap files. Memory, shared memory segments, and buffers used by the system core, etc.

Parameters:
-b Displays memory usage in bytes.
-k Displays memory usage in kb.
-m Display memory usage in MB.
　-o 　Do not display the buffer adjustment column.
　-s Continuously observe memory usage.
　-t 　Display the memory sum column.
　-v 　Display version information.

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finger

Function description: Find and display user information.

Syntax: finger [-lmsp][account name...]

Supplementary instructions: The finger command will search and display the user-related information of the specified account, including users of local and remote hosts. There is no case difference in account names. Execute the finger command alone, and it will display the login information of all current users on the local host, including account name, real name, login terminal, idle time, login time, address and phone number.

Parameters:
-l List the user's account name, real name, user-specific directory, login shell, login time, forwarding address, email status, and plan files and plans document content.
-m Excludes searching for the user’s real name.
　-s List the user's account name, real name, login terminal, idle time, login time, address and phone number.
-p Lists the user's account name, real name, user-specific directory, login shell, login time, forwarding address, and email status, but does not display the user's plan files and program file contents.

What versions of Linux are there?

Linux versions include: Deepin, UbuntuKylin, Manjaro, LinuxMint, Ubuntu and other versions. Among them, Deepin is one of the best-developed Linux distributions in China; Ubuntu Kylin is a derivative distribution based on Ubuntu; Manjaro is a Linux distribution based on Arch; LinuxMint's default Cinnamon desktop is similar to Windows XP and is simple and easy to use; Ubuntu is a desktop application Mainly Linux operating system.

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