Hello everyone, I am two black, for Linux system, whether the CPU, memory, disk drive, keyboard, mouse, or user are files, Linux system management command is the core of its normal operation. After familiarizing yourself with the common Linux file processing commands, this tutorial introduces the commands that manage the system and users.
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Commands used to manage the system and users
Hands-on practice
1. Run the kill and top commands to observe the system performance change
Start a terminal to run the top command, and then start a terminal to run the kill command, as shown in Figure 4. Figure 4 Observe the effect of the kill command on the top terminal. Use the kill command above to stop some programs: # kill SIGKILL XXX And then watch the changes in the top terminal, including memory capacity, CPU usage, system load, etc. Note that some processes cannot be aborted, but you can try them out when learning Linux commands to see how the system reacts.
2. Run the AT and halt commands to shut down the device periodically
First set the shutdown time to 17:35, enter the following code: Commands will be executed using (in order) a) $SHELL b) login SHELL C) /bin/sh at>halt ‘-i -p at> job 6 at 2004-01-01 17:35 At this point, you’ve actually entered the Shell of the Linux system and written the simplest program: halt -I -P. The end of text symbol in the preceding Shell indicates that press Ctrl+D to close the command, submit the task and exit the Shell. Job 6 at 2004-01-01 17:35 indicates that the system receives the sixth AT command and executes the command after 2004-01-01 17:35: Stop all network-related devices, shut down the system, and then power off the system.
3. Run the crontab command to perform periodic virus scanning every day
Now that you’ve seen a simple crontab command operation, here are some of the more important operations. 1. Create a file named caoproject: # crontab -e Antivir is a Linux antivirus software that is installed on your system when needed. (3) Run the crontab command to add it to the task list: # crontab caoproject All users in the system will automatically scan for viruses at 9:05 every day.
4. Run the kill command to make the modified configuration file take effect immediately
Windows users generally know that important configuration file changes often require a computer reboot for the changes to take effect. Linux, with its modular design, allows you to customize services in real time. This section uses inetd as an example to introduce some operation techniques. Inetd is a listening daemon that listens for requests to connect to Internet service processes (such as Rlogin, Telnet, FTP, and RSH) and extends the required service processes. By default, the daemons that inetd listens to are listed in the /etc/inetd.conf file. By editing the /etc/inetd.conf file, you can change inetd’s options for starting the server daemon, and then force Inetd to send a SIGHUP (signal 1) signal to the current Inetd process, causing inetd to re-read the file. This is done by using the kill command. Use vi or other editor to modify inetd. Conf, after the first to use the following command: # ps – ef | grep inetd code above show that query inetd. Conf process (PID) number, it is assumed that was 1426, and then use the following command:
# inetd kill – 1426
Then the configuration file takes effect.
The crontab command and quota command are all important commands in this tutorial. In particular, the crontab command and quota command are difficult to use. In addition, when using the kill command, pay attention to the “-9” parameter. It is best to practice not running important programs.
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