跳至主要内容

How to Kill

I always use some new release of Linux distribution, so some software froze from time to time. In order to restart it, kill command can be very handy to use for it so fast and saves lot of time compared with UI prompt.
So today, we learn how to kill effectively.

Kill

First, we should understand how to use kill. But we are surprised to find the man kill only tell us the common format:

$ kill [signal or option] PID(s)

But what’s the signal? Which one should I choose?
Signal is a kind of inter-process communication which we can take it as a message sent between processes.
And we usually use the following three signals:

Signal Name     Signal Value            Behaviour
SIGHUP                1             Hangup
SIGKILL               9             Kill Signal
SIGTERM               15            Terminate

Some kinds of signal can be ignored, like SIGTERM; but some can’t, like SIGKILL. So what we commonly use is the following:

kill -9 pid

Find the PID

Now, we know the basic about kill. So how to get the pid?
We can try the following three commands:

$ps aux | grep 'NAME'
...
$pidof NAME
...
$pgrep NAME
...

Kill By Name

Besides to kill by pid, we can also kill be name.

$pkill -9 NAME

And if we don’t know the name of a process, but we know the process id by viewing the result of ps (which seems not so common and convenient though).

ps -p 1337 -o command=

Here, the process is selected by its PID with -p. The -o option specifies the output format, comm meaning the command name.

It seems more convenient to use process name to kill. But sometimes, we don’t know the name exactly, if we choose the wrong process, we may screw our work. And in some other cases, the named process has many other siblings or child process, we may prefer kill just one of them (e.g. the names process is Java, and we just want to kill one of instances of jvm)

Last Word

Now we are ready to kill. But before we step ahead and really execute a kill command, we should understand that a process is like a file, it belongs to some user and have permission control:

  • A user can kill all his process.
  • A user can not kill another user’s process.
  • A user can not kill processes System is using.
  • A root user can kill System-level-process and the process of any user.

Ref

Written with StackEdit.

标签：

评论

发表评论

此博客中的热门博文

Spring Boot: Customize Environment

Spring Boot: Customize Environment Environment variable is a very commonly used feature in daily programming: used in init script used in startup configuration used by logging etc In Spring Boot, all environment variables are a part of properties in Spring context and managed by Environment abstraction. Because Spring Boot can handle the parse of configuration files, when we want to implement a project which uses yml file as a separate config file, we choose the Spring Boot. The following is the problems we met when we implementing the parse of yml file and it is recorded for future reader. Bind to Class Property values can be injected directly into your beans using the @Value annotation, accessed via Spring’s Environment abstraction or bound to structured objects via @ConfigurationProperties. As the document says, there exists three ways to access properties in *.properties or *.yml : @Value : access single value Environment : can access multi...
5 条评论
阅读全文

Elasticsearch: Join and SubQuery

Elasticsearch: Join and SubQuery Tony was bothered by the recent change of search engine requirement: they want the functionality of SQL-like join in Elasticsearch! “They are crazy! How can they think like that. Didn’t they understand that Elasticsearch is kind-of NoSQL 1 in which every index should be independent and self-contained? In this way, every index can work independently and scale as they like without considering other indexes, so the performance can boost. Following this design principle, Elasticsearch has little related supports.” Tony thought, after listening their requirements. Leader notice tony’s unwillingness and said, “Maybe it is hard to do, but the requirement is reasonable. We need to search person by his friends, didn’t we? What’s more, the harder to implement, the more you can learn from it, right?” Tony thought leader’s word does make sense so he set out to do the related implementations Application-Side Join “The first implementation ...
发表评论
阅读全文

Learn Spring Expression Language

When reading the source code of some Spring based projects, we can see some code like following: @Value( "${env}" ) private int value ; and like following: @Autowired public void configure (MovieFinder movieFinder, @ Value ("#{ systemProperties[ 'user.region' ] } ") String defaultLocale) { this.movieFinder = movieFinder; this.defaultLocale = defaultLocale; } In this way, we can inject values from different sources very conveniently, and this is the features of Spring EL. What is Spring EL? How to use this handy feature to assist our developments? Today, we are going to learn some basics of Spring EL. Features The full name of Spring EL is Spring Expression Language, which exists in form of Java string and evaluated by Spring. It supports many syntax, from simple property access to complex safe navigation – method invocation when object is not null. And the following is the feature list from Spring EL document : ...
发表评论
阅读全文