linux practice exam

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

sent, call the function gethostbyname () to resolve Host B, and convert the hostname to a 32-bit IP address. This process is called DNS domain name resolution .Step b:ping program sends an ICMP echo packet to the destination IP addressStep c: Convert the destination host's IP address to a 48-bit hardware address , send ARP request broadcasts within the LAN, and find the hardware address of Host B.Step d: After the ARP protocol layer of Host B receives the ARP request from host A, the hardware a

/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

:/sbin/shutdownHalt:x:7:0:halt:/sbin:/sbin/haltBash:x:505:505::/home/bash:/bin/bashNologin:x:508:508::/home/nologin:/sbin/nologin 5. Display the default shell and UID of root, CentOS, or User1 user on the current system (please create these users beforehand, if not present) [[email protected] ~]$ grep-e ' ^ (root|centos|user1) '/etc/passwd | Cut-d:-f1,3,7Root:0:/bin/bashCentos:509:/bin/bashUser1:510:/bin/bash 6, find a word in the/etc/rc.d/init.d/functions f

) 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

= "Wkiom1aliz2zxaaaaaanlsds7_o489.png"/> 6 Find all files that are not root, bin, or Hadoop under the/usr directory; 650) this.width=650; "Src=" Http://s5.51cto.com/wyfs02/M02/79/34/wKioL1aLgezCdoiXAAAFwFYBvWM900.png " Title= "7.png" alt= "Wkiol1algezcdoixaaafwfybvwm900.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 vis

Requirements: On-line system performance optimization, locating servers and online system bottlenecks Based on on-line experience data and expectation quantification Data Up Down On-line data 50 500 Test data 100 500~2000+ Test data 200 500~2000+ Test data 300 500~2000+

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

is able to receive a **/Comprehensive case1) Create child process and parent process;2) Register SIGINT non-real-time signal and sigrtmin real-time signal, and add these two signals to the process shielding signal Group;3) Register user-defined signals;4) The sub-process sends 5 non-real-time signals and sends 5 real-time signals;5) The sub-process then sends the SIGUSR1 to unblock the sigint,sigtrmin signal.6) Observe the difference between real-time and non-real-time signalsprogram example vo

int) int{Return X+y}Func Sub (x, y int) int{return x-y}Func swap (x, y String) (string, string) {return y, X}Func split (sum int) (x, y int) {x = SUM*4/9y = sum-xReturn}var c, Python, Java boolFunc Main () {Fmt. Printf ("Now you have%g problems.\n", Math. SQRT (7))Fmt. Println ("My favorite number is", Rand. INTN (10))var u64 uint64 = 1Fmt. Printf ("%d%d\n", U64, Int64 (U64))Fmt. Println (Add (42, 13))Fmt. Println (Sub (42, 13))A, B:=swap ("Hello", "World")Fmt. Println (A, B)Fmt. Println (Split

Learn more about the character test of Linux and the practice of bash scriptingOne, character test options= =: Tests whether two strings are equal, equals true, and not equal to false.！ =: Tests whether two strings are unequal, unequal to true, and equal to false.-N String: Tests whether the specified string is empty, NULL is true, and is not NULL for false.-Z String: Tests whether the specified string is n

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

package, download the installationRemove Uninstall, the configuration file is not deletedAutoremove will remove unused packagesClean Delete the buffer storage inside the hard driveUpdate download updates package list informationUpgrade Upgrade SystemSystem Core configuration file:ETC/PASSWD and Etc/shadow passwd is the account information, and Shadow is the password. Said originally in passwd can see encrypted secret law, but because passwd file is often stolen, crack root secret method, now pa