Linux Knowledge Summary (ii)

Linux Knowledge Summary (ii) directory: 1. Knowledge summary Figure 2. Review of some of the more ambiguous commands 3. Regular expressions and extended regular expressions I. Knowledge Summary chart

Two. Fuzzy Command review 1.chown

chown  可以改变文件的所属人和所属组

[[email protected] app]$ touch xiaoyufile1[[email protected] app]$ LL./xiaoyufile1-rw-rw-r--. 1 Xiaoyu xiaoyu 0 Jan 23:03/xiaoyufile1[[email protected] app]$ chown liubei xiaoyufile1chown:changing Ownershi P of ' xiaoyufile1 ': Operation not permitted[[email protected] app]$ exitlogout[[email protected] app]# chown Liubei xiaoyufile1[[email protected] app]# LL./xiaoyufile1-rw-rw-r--.  1 liubei xiaoyu 0 Jan 23:03/xiaoyufile1[[email protected] app]# chown Xiaoyu xiaoyufile1[[email protected] app]# LL./xiaoyufile1-rw-rw-r--. 1 Xiaoyu xiaoyu 0 Jan 23:03/xiaoyufile1[[email protected] app]# chown Liubei.liubei Xiaoyufile1[[email pro Tected] app]# LL./xiaoyufile1-rw-rw-r--. 1 liubei liubei 0 Jan 23:03/xiaoyufile1[[email protected] app]# chown Xiaoyu.xiaoyu Xiaoyufile1[[email pro Tected] app]# LL./xiaoyufile1-rw-rw-r--. 1 Xiaoyu xiaoyu 0 Jan 23:03/xiaoyufile1[[email protected] app]# su-xiaoyulast Login: Sat Jan 23:00:59 CST 2018 on pts/0[[email protected] ~]$ cd/app[[email protected] app]$ chown. Liubei Xiaoy Ufile1chown:changing Group of ' xiaoyufile1 ': Operation not permitted

根据以上的命令结果可以得出结论:1.当前用户为文件所属人时，无权更改文件的所属人和所属组2.只有当前用户为root时,才可以更改文件所属人和所属组 3.命令方式为      chown 所属人.所属组 filename    更改文件的所属人和所属组

2.chmod

 The use of chmod numbers I have roughly memorized (chmod xxx file names), but the notation notation is quite strange [[email protected] app]# LL./xiaoyufile1-rw-rw-r--. 1 Xiaoyu 0 Jan 23:03/xiaoyufile1 [[email protected] app]# chmod o-w xiaoyufile1 [[email protected ] app]# LL./xiaoyufile1-rw-rw-r--. 1 Xiaoyu 0 Jan 23:03/xiaoyufile1 [[email protected] app]# chmod o=rwx xiaoyufile1 [[Email protect ED] app]# LL./xiaoyufile1-rw-rw-rwx. 1 Xiaoyu 0 Jan 23:03/xiaoyufile1 [[email protected] app]# chmod g=rwx xiaoyufile1 [[Email protect ED] app]# LL./xiaoyufile1-rw-rwxrwx. 1 Xiaoyu 0 Jan 23:03/xiaoyufile1 [[email protected] app]# chmod u=rwx xiaoyufile1 [[Email protect ED] app]# LL./xiaoyufile1-rwxrwxrwx. 1 Xiaoyu 0 Jan 23:03/xiaoyufile1 [[email protected] app]# chmod a-w xiaoyufile1 [[email protected ] app]# LL./xiaoyufile1-r-xr-xr-x. 1 Xiaoyu 0 Jan 23:03/xiaoyufile1 [[email protected] App]# chmod a-rx xiaoyufile1 [[email protected] app]# LL./xiaoyufile1----------. 1 Xiaoyu 0 Jan 23:03/xiaoyufile1 [[email protected] app]# chmod u+rx xiaoyufile1 [[Email protecte D] app]# LL./xiaoyufile1-r-x------. 1 Xiaoyu 0 Jan 23:03/xiaoyufile1 "The results from the above command can be concluded as follows: 1. First usage: chmod u/g/o=xxx filename Changes the permissions of the person/group/other person to XXX 2. the second usage; chmod u/g/o/a-/+ XXX filename will file owner/affiliation Group/other person/everyone plus XXX permissions 3. Disadvantage: Only one permission can be manipulated at a time, the more cumbersome advantages: more accurate

3.ACL Access Control List

ACL权限:     由于系统用户过多,会出现不同用户有着不同的权限需求,所以普通的 文件所属人，文件所属组，其他人这种普通的权限设置方式便不能满足要求。而ACL权限可以给特定的用户以特定的访问权限来实现其要求。     1.ACL设置个人权限

     在设置后，ll命令会显示权限会多一个加号，此时应该调用getfacl 路径名/ 查看权限,会发现此时多了一个user:liubei:rwx权限，原本liubei在文件夹里是没有写入文件的权限的，而在设置之后便可在此文件夹里写入内容     2.ACL设置组权限

            可以在图中看到，liubei,zhangfei都属于shuguo组，在设置了组权限之后，两者均可在文件夹里写入内容。故ACL也可设置组权限3.清空ACL权限

可以看到原本在ll命令下是有+的，在输入命令后+消失了，即取消了ACL权限。

ACL Summary

设置单用户： sefacl -m u:用户名:xxx(权限) 路径设置组:           sefacl -m g:组名:xxx    (权限) 路径取消ACL:        setfacl -b 路径权限优先级：owner > acl user > group 与 acl group 谁的权限多，谁优先  > other

Three. Regular expressions and extended regular expressions

This part doesn't have to be said, it takes a lot of practice

Add user bash, Testbash, basher, SH, nologin (whose shell is/sbin/nologin) to find the/ETC/PASSWD user name with the shell name of the row

cat /etc/passwd | grep "\(^.*\)\>.*\<\1$"

Displays three user root, Mage, Wang's uid, and default shell

cat /etc/passwd | grep -w "^root\|mage\|wang\>"|cut -d":" -f3,7

Find the line at the beginning of the/etc/rc.d/init.d/functions file that follows a word (including an underscore) followed by a parenthesis

cat /etc/rc.d/init.d/functions|grep -w "^[[:alpha:]]*_.*[(][)].*"

Use Egrep to remove its base name in/etc/rc.d/init.d/functions

 echo  "/etc/rc.d/init.d/functions"|egrep -o "\<[[:alpha:]]*$"

Use Egrep to remove the directory name from the path above

echo  "/etc/rc.d/init.d/functions"|egrep -o "^.*/"

Displays lines in the/proc/meminfo file that begin with size S

cat /proc/meminfo |grep -i ^s

Displays lines in the/etc/passwd file that do not end in/bin/bash

cat /etc/passwd | grep -v /bin/bash

Show user RPC default shell program

    cat /etc/passwd |grep "^rpc\b" |cut -d: -f71

Find the two-bit or three-digit number in the/etc/passwd

cat /etc/passwd |grep "\b[0-9]\{2,3\}\b"

A line that displays at least one whitespace character in a CentOS7/etc/grub2.cfg file, followed by a non-whitespace character

    cat /etc/grub2.cfg |egrep "^[[:space:]]+[[:graph:]].*"

Find the line that ends with ' LISTEN ' followed by any number of whitespace characters in the result of the "Netstat-tan" command

netstat -tan |grep "LISTEN[[:space:]]\+$"

Displays the user name and UID for all system users on CentOS7

cat /etc/passwd |cut -d: -f1,3 |grep -v root |grep "\b[[:digit:]]\{1,3\}\b$"

Linux Knowledge Summary (ii)