comptia linux practice test

Summary:Based on the list definition of the Linux kernel, this paper attempts to complete the related interface design, and constructs the test case to realize the usage of the list interface.Body:Let's start by looking at the list interfaces provided by the Linux kernel as follows:struct head_node{struct head_node* pre;struct head_node* next;};That is, there are

forcibly compress the file. Ignores the existence of a file name or a hard connection and whether the file is a symbolic connection.-H or--help online Help.-L or--list lists information about the compressed file.-L or--license display version and copyright information.The original file name and time stamp are not saved when the file is compressed by-N or--no-name.-N or--name compress the file, save the original file name and time stamp.-Q or--quiet does not display a warning message.-R or--recu

: Read file map **/int main (int Argc,char **argv) {if (argc! = 2) err_quit (" usage:. main Map Note points:1. Memory mapping cannot (and cannot) change the size of the file;2. The valid address space available for interprocess communication is not entirely limited to the size of the mapping file, but should be based on the size of the memory page (see test below);3. Once the file is mapped, all access to the mapped area is actually access to the memo

:/usr/local/bin:/usr/local/sbin:~/bashExport PATHDeclare-i sum=0For I in {1..100}; DoLet remainder= $I%3If [$REMAINDER-eq 0]; ThenLet sum= $SUM + $IFiDoneecho "$SUM"Exercise Three:Write a scriptShows all default shell-bash users and default shell-/sbin/nologin users on the current system, respectively.and statistics of the total number of Shell users, showing the results are as follows:Bash,3users,they Are:root,redhat,gentooNologin,2users,they are:bin,ftp#!/bin/bash#program:#显示当前shell下面的用户#histo

Linux inter-process communication (IPC) Programming Practice (9) System V semaphores-A toolset for encapsulating a semaphores operationMain API # include # Include # Include Int semget (key_t key, int nsems, int semflg );Int semctl (int semid, int semnum, int cmd,...); int semop (int semid, struct sembuf * sops, unsigned nsops ); SemgetInt semget (key_t key, int nsems, int semflg);/** Example 1:

users have write permission files;find/etc/init.d/-perm-111-a-perm-00218, so that ordinary users can use/tmp/cat to view/etc/shadow files;chmod U+s/tmp/cat19, create the directory/test/data, let a group of ordinary users have write permission to it, and all the files created by the group of directories belong to the group, in addition, each user can only delete their own files;Mkdir/test/data New Directory

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) this.width=650; "src=" Http://s4.51cto.com/wyfs02/M01/79/BD/wKioL1aaFgyzqgUwAAAhpWUiLqI409.png "style=" float: none; "title=" 7.png "alt=" Wkiol1aafgyzqguwaaahpwuilqi409.png "/>7 , one day the system was invaded, hackers in your system to leave the Trojan file:You now need to find all the files on the current system that are not owned by the master or group and have been visited in the last week;In addition, it is necessary to find all files of more than 20k and type ordinary files in/etc dire

Linux signal Programming Practice (3) Signal Representation in the kernel (sigaction sigqueue) Representation of signals in the kernel The processing action of the actually executed signal is called the Delivery, the State between the signal generation and the Delivery, and the Pending ). A process can Block a signal. When a blocked signal is generated, it remains in the pending state until the process unb

Tomcat default portCd/usr/local/tomcat/confVI server.xml Search 8080, find the following section configurationChange 8080 to 80 and restart the Tomcat service when you're done.Five, add a virtual host to Tomcat,1,vi Server.xml, find Host name= "www.test.com" appbase= "/data/tomcatweb"Unpackwars= "false" autodeploy= "true"Xmlvalidation= "false" Xmlnamespaceaware= "false" >，Save exit, close Tocat, and start Tomcat.2, create AppBase mkdir-p/data/tomcatwebVi/data/tomcatweb/index.jsp (Write a time f

memoryError_log/data/logs/nginx/error.log Crit;Pid/elain/apps/nginx/nginx.pid;Worker_rlimit_nofile 65535; #nginx能打开文件的最大句柄数, it is best to keep the value of ulimit-n consistent with the Ulimit-shn 65535 settingEvents {Use epoll; #使用epoll的I/O modelconnections 20000; #每个进程允许的最多连接数worker_connections 65535; #该值受系统进程最大打开文件数限制, you need to use the command ulimit-n to view the current settingsmaxclients=65535*2}http {include mime.types; #mine. Types define each file type imageTypes {text/html html;ima

several ways to terminate a process(1) Normal exitreturn from main function [Return] Call exit Call _exit/_exit(2) Abnormal exit call Abort to generate Sigabout signal terminated by signal CTRL + C [SIGINT] ... (not completely, such as return/pthread_exit, etc.)Test [Exit/_exit]Try to view the printout of the program int main () { cout The graph shows that the system call _exit directly into the kernel, and the C library function is through a serie

Sem_open (key_t key) { int semid = Semget ( Key, 0, 0); if (Semid = =-1) err_exit ("Sem_open error"); return semid;}Shmctlint semctl (int semid, int semnum, int cmd, ...);Control semaphore SetParametersSEMID: Signal set identification code returned by Semget semnum: sequence number of signals in the signal set (note: Starting from 0 The semaphores in a set is numbered starting at 0.) cmd: The action to be taken (common values are as follows) If the function requires a fourth arg

function pointer inside the parenthesesModule destructor: The function called when executing the rmmod instruction unload module. Function prototype is module_exit ()Module License Statement: The function prototype is Module_license (), which tells the kernel which license the program uses, otherwise it will prompt the module to contaminate the kernel when it is loaded. The GPL is generally written.Header file Module.h, this file must be included;Header file Kernel.h, containing commonly used k

Read end Shut_wr Close the Write end Shut_rdwr Both read and write off Close terminates two directions of data transfer, shutdown can selectively terminate data transfer in a certain direction or terminate data transfer in two directionsSHUTDOWM How=1 can guarantee that the peer receives an EOF character, regardless of whether other processes have opened the socket.Close does not guarantee that it will be sent until the socket reference count is re

registration of the process is revoked. The process must call Mq_notify again to reregister (if necessary), but be aware that re-registration is placed before the message is read from the message queue and not after (as with the example program);Attached-View the POSIX message queue that has been successfully created#其存在与一个虚拟文件系统中, you need to attach it to your system to viewmounting the message queue filesystem On Linux, message queues is created in

of the extra directory, and then call it in the form of include.8 Nginx alias and connection status information configuration #别名其实就是以相应的别名配置虚拟主机, then use the rewrite rule to jump to the primary domain.Specifically write a configuration file with the following contents:server {Listen 80;server_name etiantian.com;Rewrite ^ (. *) http://www.etiantian.com permanent;}This file will then be called in the Nginx file: include extra/www_alias.conf That is, configure a virtua

/wKioL1Xtnv-xHD9EAABtXGZ9Jno537.jpg "title=" 17.png "alt=" Wkiol1xtnv-xhd9eaabtxgz9jno537.jpg "/> - , so that ordinary users can use/tmp/cat to view/etc/shadow files;650) this.width=650; "src=" http://s3.51cto.com/wyfs02/M01/72/D1/wKiom1XtnPqxNlopAAA-O9Rpqgo408.jpg "style=" float: none; "title=" 18.png "alt=" Wkiom1xtnpqxnlopaaa-o9rpqgo408.jpg "/>650) this.width=650; "src=" http://s3.51cto.com/wyfs02/M02/72/CE/wKioL1XtnyTSyVxlAAFAitTWYgI722.jpg "style=" float: none; "title=" 18.2.png "alt=" Wkio