Article Title: How to kill botnets in Linux. Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source.
1) Check the current zombie Process Information
# Ps-ef | grep defunct | grep-v grep | wc-l
175
# Top | head-2
Top-15:05:54 up 97 days, 4 users, load average: 0.66, 0.45, 0.39
Tasks: 829 total, 1 running, 479 sleeping, 174
child process goes into a zombie state.
Zombie Process: When a child process exits, the parent process does not properly handle the SIGCHLD signal it emits, causing the child process to stay in a zombie state waiting for the parent process to bury it.
POSIX signal processing
POSIX represents a portable operating system interface (Portable
1, uptime
[Email protected] ~]# uptime
15:08:15 up 98 days, 4:19, 2 users, load average:0.07, 0.29, 0.14The current time system has been running for how many users logged on the current system is 1 minutes, 5 minutes, 15 minutes ago to the present load situationLoad average is the average length of the queue and the number of processes waiting to be executed in the queueThe lower the value, the more likely the process is to be processed by the CPU immediately, and the higher it is,
Process Status:1) Overview of the status of the process:1.1) Running (R), running or going to run1.2) interruptible (S), blocked while waiting for an event, may be activated by a signal1.3) uninterruptible (D), blocked while waiting for an event, will not be activated by the signal1.4) Stopped (T), terminated as a result of task control or external tracing, for example: Strace1.5) Zombie (Z), zombie, but it
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(Word-alignedbinary code, WABC) compresses the index. This encoding has the advantage of byte operations, its compact binary feature not only guarantees the compression performance of indexes, but also improves the decoding speed of inverted list during query.
Performance ofcompressed inverted list caching in search engines considers the index compression and index cache mechanisms in the search engine, and compares the performance of several compression algorithms, such as bit encoding
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Up to now, there have been at least three methods for struts actionform.:Common,DynamicAndLazy.
Therefore, you can have a lot of options in your own development. If you are safe first, you can use common. If you prefer XML, use dynamic.
If you are lazy, use lazy actionform.
You only need to select one of the three actionform methods provided by struts.
The following describes lazy actionform:
If you like the powerful features of struts (for example, this actionform has multiple options) and you
ProgressDialog is displayed, but the real-time progress is not displayed.
Let's take a look at the layout file:
It is a simple ImageView control and a Button control. When you click the Button control, a ProgressDialog pops up, starts an asynchronous task, and downloads an image from the network, and update it to our ImageView. Note that if we want to use a mobile phone to access the network, we must authorize it. In the future study, we will explain in detail the authorization knowledge in An
, hostname, port and file creationPublic URL (String protocol,string host,int port,string file)URL encapsulates object informationThe URL object encapsulates information about the object, such as the port number of the URL object, the header content, the hostname, the protocol name, and so on./** * @FileName: Urltest.java * @Package: Com.socket * @Description: TODO * @author: LUCKY * @date: December 11, 2015 Morning 8:48:34 * @v Ersion V1.0 */package com.socket;import java.awt.image.imageproduce
://ww2.sinaimg.cn/mw690/81b78497jw1eic3rqwb6mj20qj0dzwfu.jpg "width=" 690 "height=" 363 "title=" File System "alt=" 81b78497jw1eic3rqwb6mj20qj0dzwfu.jpg "/>Assuming that a file's properties and permissions information is stored in the Inode number 3rd, and the actual file data is stored in the 1, 4, 6, 11 of the four blocks, then when the operating system to access the file, it can arrange the reading order of the disk, you can scan the contents of 4
high speed and a high capacity similar to the CPU, and the cost is low. The high-speed cache solves the speed problem of the storage system, while the secondary storage solves the capacity problem of the storage system. The multi-level hierarchical storage system can effectively solve the contradiction between the storage speed, capacity and price.
2. How does a zombie process generate in Unix/Linux? What are the dangers? How to avoid it? (10 points)
), it needs to send a signal to the parent process, which needs to get information about the child process when the parent process is signaled, so the task_struct of the child process cannot be deleted at this time. In addition, each process has a kernel-state stack, and when the process calls exit (), it always uses the kernel-state stack before switching to another process, so when the process calls exit (), when the necessary processing is done, the state is set to Task_dead and switched to a
, environment, and file descriptors.
three. Orphan process and zombie process In Linux, the child process is always generated by the parent process, the child process and the parent process are running at the same time, the parent process cannot predict when the child process will end, and when a process finishes its work, the parent process needs to call the Waitpid system call to get the terminating state of the child process. The orphan proce
encountered a null pointer to the code as a scrap code, will execute, but will not have any effect
Zombie *zom =[zombie zombiewithblood:100 attack:20 speed:10];
[Zom attack];
return 0;
}
Zombie.h
Oc3_ inheritance, convenience constructors, initialization methods
//
Created by Dllo on 15/7/16.
Copyright (c) 2015 CML. All rights reserved.
//
#import
@interface Zombie:nsobject
Characteristics
{
Nsinteger
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