Linux commands and their use
Currently, the family of UNIX-like operating systems (OS) based on the Linux kernel is gaining increasing popularity among computer users. This is due to the fact that the developers of various distributions of this OS provide a fairly good graphical interface and, not least, most of them are absolutely free. We will not dwell on the advantages of “Linux” over the systems of the Windows family that are loved by tens of millions of users, because this is the eternal dispute between Linux and Windows users, and there is no end to it. Talk about what Linux commands are and how you can use them.
Many desktop operating systems of this family use a graphical interface, and a terminal emulator is used to enter commands. The latter, for example in the most popular Ubuntu system, is invoked by pressing the key combination Ctrl + Alt + T. In Linux, teams are separate independent programs. And any programmer can change them as he pleases, if he has enough qualifications, otherwise the consequences are unpredictable.
Classification of system commands
Consider the basic functions that may need a user working with a graphical interface. First we say that all Linux system commands are classified into the following groups:
1) General purpose.
2) System management.
3) Management of processes and tasks.
4) User management.
5) Terminal settings.
6) File system and disk management.
This command displays in a formatted format a reference manual for a command or program that can be run in a terminal. The command syntax is "man command_name".
Linux OS is designed so that users get a minimum, but sufficient for solving the tasks set of rights. However, there is a special account under the name of root (superuser), whose owner has the right to perform all operations without exception. Almost all system commands are executed only as root. To transfer the rights to perform such operations to the user, there is a “sudo” command, which is entered like this: “sudo command_name”. After that, the system asks for a superuser password, and, if everything is correct, you get exclusive rights to everything.
Commands "ps" and "kill"
These two Linux commands are used when a process is frozen on the system. This happens sometimes. The utility "ps" lists the processes in the system. "Kill" allows you to kill a process by ID. If “ps” is called along with “sudo”, all processes running on the system are output, not just those that belong to the current user. First we type “sudo ps -aux”, then we enter a password for the system request. The -aux options allow you to display all processes associated with this terminal and disconnected from it, as well as sort them by user ID. In the resulting list, we find the identifier of the desired process, for example, “2145”, and kill it with the command “kill 2145”.
The "rm" instruction allows you to delete files or directories from the system. Like many other Linux commands, the user may not use it in the terminal, but work with files in the graphical interface. But we will describe this program for what. There used to be a dangerous command “sudo rm -rf /”, which, without asking for confirmation, completely deleted the system. This is currently not working. But if you add the key “--no-preserve-root”, i.e. “sudo rm -rf /“ --no-preserve-root ”, the whole system is killed. The rm -rf / * option is also possible, which also kills it. Well, perhaps, all the basic commands of Linux.So be careful. Good luck!