This article, we came to Linux strange side ......
do you know? In our daily use of Unix (and Linux) and various branches of the system, there are some strange commands or processes, they are creepy, some are indeed poisonous, but some are useful. Here's a brief look at these guys now.
1. daemon
daemon has a Chinese name on a very large, called 守护进程.
There is a saying, if there is no daemon on Unix, Unix then it will not be the same.
It is very personal, is a process running in the background and is not a control terminal, which mostly start with the system and start, no special circumstances will remain closed until the system is running.
It's there for our users and the system itself to provide a useful service. Common are httpd, mysqld, syslogd, are generally daemon name will dend.
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2. zombie
Zombie , zombie? What the hell? Listening to scary.
However, it is in the middle of Linux is that when a process is killed, in fact, it will not disappear immediately, but turned into a zombie, namely zombie process, and then wait for the completion of its parent process to gather information will be cleared.
In general this information gathering process will be completed soon, but sometimes it's busy parent, the zombies will always stay in our system.
From time to time during system operation will have some zombie process, we can not kill them directly, because they are dead, we can only resort to other means, such as to kill its parent process, and then to recover the corpse by the init process .
Emergence of zombie process that produced it is usually expressed in addition to the problem, and it will consume resources, to prevent its appearance.
3. kill
the kill , a callous words.
As the name suggests, kill is a kill command for the process, its use is simple and crude. When you find a process too much memory or CPU resources occupancy and had a negative impact, it is recommended that you can get rid of it directly kill.
If you encounter a zombie process can not kill? Do not panic, go to its parent process it, according to the above-mentioned method to deal with.
4. cat
CAT , cat? What is that strange things? In addition to Linux, there are zombies cat?
In fact, cat command is short for concatenate, which is connected to the mean, so explain what you understand.
Its role is combined file. In addition, you can even use this handy command to view the contents of the file.
5. tail
tail , tail. This strange command relatively easy to explain.
When the last n rows you want to view the file, use the tail command is very convenient.
In addition, when you want to monitor files, you can also use it. For example, observing the log file, tail command displays the contents of the tail and can be updated in real time, is not very powerful it?
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6. which
Which , I do not look strange on the first few commands and witch (Witch) mixed up. It is not the kind of dark fairy tale wicked witch, it is which, is responsible for printing it passed to the location of any associated command file guy.
For example, we want to get Python's position, we can use which python, it will print the location of each version of Python on your system.
7. crypt
crypt , basement, this command is also easy to understand.
When you want to protect your stuff is not known by others, into the basement locked up is a very good way.
Meaning crypt in Linux is encrypted, now called mcrypt, when you want to encrypt files without being read others, this command will be very convenient. As with most Linux commands, you can use the crypt alone, the system can also be used in the script.
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8. shred
Shred , shred. I think you've seen here in these strange words flattering.
It is a very hard guy, is to shred files. When we want to delete a file, we will use the rm command, but this is a means for recovery, then we do not want people to restore how to do? Yes, sherd role in this regard. shred many times before covering the space occupied by the file. So, use this command that should be psychologically prepared, because gods can not put out.
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