Shulou(Shulou.com)06/03 Report--

Linux/Centos7 account and rights management user account, group account query account information setting file and directory permission setting file and directory attribution I. introduction

​ as a multi-user, multi-task (Multi-Users,Multi-tasks) server operating system, Linux provides a strict rights management mechanism, which mainly restricts resources from two aspects: user identity and file permissions. Linux controls access to resources based on the user's identity.

User account category: superuser-root, most privileged ordinary user-Custom user Anonymous user (nobody) is similar to Guest program user in Windows-controlling programs and services Unable to log in to a group account-- a collection of users (in fact, it can be thought of as a collection of user permissions)-- basic groups (private groups)-- created with the same name as the user (or you can set it yourself), but when you create a user, there must be an additional group (public group)-- create an empty group directly, you can add existing users and set permissions for the group. All users in this group have this permission UID and GIDUID (User IDentity)-- user identification number (by default 0 means root 1: 999 means (system) program user 1000: 60000 means (login) ordinary user) GID (Group IDentity)-- group identification number

2. User account file / etc/passwd-- saves user name, host directory, login shell and other basic information [root@lokott ~] # head-2 / etc/passwdroot:x:0:0:root:/root:/bin/bashbin:x:1:1:bin:/bin:/sbin/nologin

Root ​: X: ​ 0VOUL0ROTROGRAPHERUTION rootVOUBING Bash ​-separated by colons, explain one by one below.

Root-- user account name xmai-password encrypted using encryption algorithm. Here is the full name of the UIDroot-- user of the basic group account to which the user UID number 0Mel is not displayed. You can fill in the user details / root-- host directory / the login Shell/etc/shadow-- of the bin/bash-- specified user to save the user's password, account validity, etc. [root@lokott ~] # head-2 / etc/shadow / / View the first two lines of information root:$6 $P0mVYDgJo8HZnWlyogoYlITJyv.h.6wS sign OCuAdc61QoWTkYJONdy9aAjRW4Cpmc5Mor40xn RiZ9Hi1PzhVoX5Chur4Vf8JmKO1JmKO1purpur0pur99999JmKO1JMJJJJJJJJJJJO1PzhVoX5Chur4Vf8JmKO1JMKO1V014999JJJJJJJJJJJJJJJJJJO1PzhVoX5Chur4Vf8JmKO1

Root:$6 $P0mVYDgJo8HZnZWlyogoYlITJyv.hP.6wSAccording to OCuAdc61QoWTkYJMcONdy9aAjRW4Cpmc5Mor40xn RiZ9Hi1PzhVoX5Chur4VfFB8JmKO1PzhVoX5Chur4VfFB8JmKO1 is separated by a colon, which is explained one by one below

Root-- user account name

Bold-indicates the password encrypted by the encryption algorithm. The password entered by login is invalid.

::-- the content between is the last modified time

0mi-the minimum valid days of the password (0 means it can be changed at any time)

99999muri-the longest valid days of the password

7mi-7 days in advance to remind the user that the password will expire

::-- indicates the operation processing after the expiration of the password and account (basically negligible)

Second, manage user accounts 1. Add user account-- useradd command

Option

-u-- specifies the UID number of the user, and the UID number is not used by other users-d-- specifies the location of the user's host directory (does not take effect when used with-M! )-emure-account expiration time (expiration time)-gmure-basic group-Gmure-additional group-Mmuri-no-home directory-s-specify the login shell of the user

Example: useradd-d / opt/mike (- g mike)-G caiwu-s / sbin/nologin mike

[root@lokott] # useradd-d / opt/mike-G caiwu-s / sbin/nolgin mike / / Note you need to have a caiwu group first-- groupadd caiwu [root@lokott ~] # tail-2 / etc/passwd / / View the last two lines of information in the passwd file lokott:x:1000:1000:lokott:/home/lokott:/bin/bashmike:x:1001:1001::/opt/mike:/sbin/nolgin [root@lokott ~] # tail-2 / etc/groupcaiwu:x : 1002:mikemike:x:1001: [root@lokott ~] # tail-2 / etc/shadowlokott:$6 $aq3AU9oDZf pick ERE2DruOl.zBTLNqbsPDdsJYE0yU3Wa7EUU1SonR3rUQ616PsgA2u.DtQ99ecTUbdw2y2RhmlaL75WlcqMsfEUNretgb0RmlaL99999MsfEUNretgb0Rm18192 0RV 018 192RV 0RV 99999MsfEUNretgb018192 0RV: [root@lokott ~] # id mike / / View mike's id information uid=1001 (mike) gid=1001 (mike) group = 1001 (mike) 1002 (caiwu) [root@lokott ~] # ls / home/ because-d specifies the user's host directory So the home directory is created in the specified / opt/mike directory demo lokott [root@lokott ~] # ls / opt/demo01.txt mike rh test [root@lokott ~] # 2. Set / change user password (password) passwd

Passwd option. User name

-d clear password-l Lock-S to see if it is locked or unlocked (uppercase! )-u unlock [root@lokott ~] # useradd-d / opt/lisi-s / sbin/nologin lisi [root@lokott ~] # tail-2 / etc/passwdlokott:x:1000:1000:lokott:/home/lokott:/bin/bashlisi:x:1001:1001::/opt/lisi:/sbin/nologin / / where / sbin/nologin means that the user cannot log in to [root@lokott ~] # passwd lisi to change the password of the user lisi. New password: / / requires you to enter an invalid password: the password is less than 8 characters / / because you have entered a simple password, you can continue to enter it once, of course, if you have a complex password, you can re-enter the new password: passwd: all authentication tokens have been successfully updated. [root@lokott ~] # su-lisi Last failed login: April 31 18:49:45 CST 2019 from: 1:1 the most successful login followed by a failed login attempt. This account is currently not available. / / unable to log in Because the login shell is / sbin/nologin [root@lokott ~] # pwd/root [root@lokott ~] # vim / etc/passwd / / enter the passwd file to change the user's / sbin/nologin to / bin/bash [root@lokott ~] # su-lisi / / root when you switch users, you do not need to enter a password for the last login: October 31, October 31, 18:52:42 CST 2019pts/2 Log in to lisi user / opt/lisi [lisi@lokott ~] $su / / on [lisi@lokott ~] $pwd / / equivalent to su-root. The results below show that ordinary users need a password when switching root. The password entered does not display the password: [root@lokott lisi] # pwd/opt/lisi [root@lokott lisi] # cd [root@lokott ~] # pwd/ / indicates that the password that switches to the root user / root [root@lokott ~] # passwd-l lisi / / locks the password of user lisi. Passwd: operation succeeded [root@lokott ~] # passwd-S lisi / / View the password status of lisi users lisi LK 2019-10-31 0 99999 7-1 (password is locked.) [root@lokott ~] # su-lisi Last login: [lisi@lokott ~] $pwd / / on CST 2019pts/2 at 19:01:10 on October 31 on Thursday, you can see that although root is locked, root can switch login without the need for a password / opt/lisi [lisi@lokott ~] $[root@lokott ~] # passwd-u lisi to unlock the password of user lisi. Passwd: operation succeeded [root@lokott ~] # passwd-S lisilisi PS 2019-10-31 0 99999 7-1 (password has been set, use SHA512 algorithm.)

The example can be summarized as follows:

Among them, the / sbin/nologin user cannot log in directly and is switched to login after the passwd-l lisi is executed. The user cannot log in in the graphical user interface, but the login can be switched from the root user (and the root switch does not require a password) 3. Modify the attributes of the user account usermod-u modify the user's UID number-d modify the user's host directory location-e modify the user account expiration time-s specify the user's login shell-l change the user login account name-L lock-equivalent to passwd-lcomeU unlock-equivalent to passwd-u

Among them, 1-4 is similar to useradd and demonstrates the following operation of-l

[root@lokott ~] # usermod-l zhangsan lisiusermod: user lisi is currently used by process 71736 [root@lokott ~] # ps-ef | grep lisiroot 71735 71117 0 19:01 pts/2 00:00:00 su-lisilisi 71736 71735 0 19:01 pts/2 00:00:00-bashroot 72433 71829 0 19:11 pts/2 00:00:00 su-lisilisi 72435 72433 0 19:11 pts/2 00:00:00-bashroot 73325 72935 0 19:24 Pts/2 00:00:00 grep-- color=auto lisi [root@lokott ~] # kill 71735 / / can also be restarted Automatically ends the process [root@lokott ~] # Session terminated, killing shell... ... Has been killed. [root@lokott ~] # exit [root@lokott ~] # usermod-l zhangsan lisi [root@lokott ~] # tail-2 / etc/passwdmike:x:1001:1001::/opt/mike:/sbin/nolginzhangsan:x:1002:1003::/opt/lisi:/bin/bash / / only changed the lisi user name, but the name of the home directory is still lisi [root@lokott ~] # ls / optdemo01.txt lisi mike rh test [root@lokott ~] # 4. Delete user account userdel

-r delete the host directory together, and the following demonstration follows the above operation

[root@lokott ~] # tail-2 / etc/passwd / / shows two users mike:x:1001:1001::/opt/mike:/sbin/nolginzhangsan:x:1002:1003::/opt/lisi:/bin/bash [root@lokott ~] # userdel-r mike / / Delete mike users and "copy home" [root@lokott ~] # tail-3 / etc/passwd tcpdump:x:72:72::/:/sbin/nologinlokott : x:1000:1000:lokott:/home/lokott:/bin/bashzhangsan:x:1002:1003::/opt/lisi:/bin/bash [root@lokott ~] # ls-l / opt/mike / / indicates that-r removes the specified home directory ls: unable to access / opt/mike: there is no file or directory [root@lokott ~] # ls / opt/ / currently in / opt has lisi home directory (the name has been changed to zhangsan above) demo01.txt lisi rh test [root@lokott ~] # userdel-r zhangsan / / Delete zhangsan users At the same time, the lisi directory will be deleted [root@lokott ~] # tail-3 / etc/passwdpostfix:x:89:89::/var/spool/postfix:/sbin/nologintcpdump:x:72:72::/:/sbin/nologinlokott:x:1000:1000:lokott:/home/lokott:/bin/bash [root@lokott ~] # ls-l / opt / / because the zhangsan user is deleted and-r delete the home directory If you do not add-r, the total amount will not be deleted. 1 root root 0 October 31 16:19 demo01.txtdrwxr-xr-x. 2 root root 6 March 26 2015 rhdrwx-wx-wx. 2 root root 32 October 31 18:33 test [root@lokott ~] # useradd wang / / create a new user [root@lokott ~] # usermod-l sung wang / / change to user name [root@lokott ~] # tail-2 / etc/passwd / / View passwd information lokott:x:1000:1000:lokott:/home/lokott:/bin/bashsung:x:1001:1003::/home/wang:/bin/bash [root@lokott ~] # userdel sung / / Delete sung users but do not delete wang [root@lokott ~] # ls / home/demo lokott wang5. The initial configuration file of the user account

File source-the new user account is copied from the / etc/skel directory (use ls-an in the cd to home directory)

~ / .bash_profile means to be loaded after entering bash ~ / .bashrc users are loaded when logging in ~ / .Execution is executed when bash_logout logs out. 3. Manage group account group account files-similar to user account files / etc/group: save group account basic information / etc/shadow: save group account password information (usually not set) 1. Add group account groupadd command

Groupadd option group name

-g-- specify GID

[root@lokott ~] # groupadd lisi / / add lisi group [root@lokott ~] # tail / etc/group / / View group information postdrop:x:90:postfix:x:89:stapusr:x:156:stapsys:x:157:stapdev:x:158:tcpdump:x:72:lokott:x:1000:printadmin:x:985:caiwu:x:1002:lisi:x:1003: [root@lokott ~] # groupadd- G 1005 wangwu / / add wangwu group and configure it with GID of 1005 [root@lokott ~] # tail-2 / etc/grouplisi:x:1003:wangwu:x:1005: [root@lokott ~] # 2. Add group members and delete group members add-gpasswd-an adding a user to the group does not overwrite-d removes a user-M comma-separated set group membership list from the group, overwriting group members Kick out the original [root@lokott ~] # tail-2 / etc/group / / View group information lisi:x:1003:wangwu:x:1005: [root@lokott ~] # tail-2 / etc/passwd / / View user information tcpdump:x:72:72::/:/sbin/nologinlokott:x:1000:1000:lokott:/home/lokott:/bin/bash [root @ lokott ~] # useradd lisi / / add lisi user will fail Because the above shows that the lisi group already exists-if you want to add this user to the group, use the-g parameter. [root@lokott ~] # useradd-g lisi lisi / / add lisi users to the lisi group [root@lokott ~] # useradd zhangsan / / add another zhangsan user [root@lokott ~] # tail-2 / etc/passwd / / View user information lisi:x:1001:1003::/home/lisi:/bin/bashzhangsan:x : 1002:1006::/home/zhangsan:/bin/bash [root@lokott ~] # gpasswd-a lisi wangwu / / add lisi to wangwu group (first wangwu group) adding user "lisi" to "wangwu" group [root@lokott ~] # id lisi / / View UIDuid=1001 (lisi) gid=1003 (lisi) group of lisi = 1003 (lisi) 1005 (wangwu) [root@lokott ~] # gpasswd-d lisi wangwu / / removing lisi from the wangwu group is removing the user "lisi" from the "wangwu" group [root@lokott ~] # id lisi / / View lisi's UID No longer belong to wnagwu group uid=1001 (lisi) gid=1003 (lisi) group = 1003 (lisi) [root@lokott ~] # tail-5 / etc/passwd / / display user information postfix:x:89:89::/var/spool/postfix:/sbin/nologintcpdump:x:72:72::/:/sbin/nologinlokott:x:1000:1000:lokott:/home/lokott:/bin/bashlisi:x:1001:1003::/home/lisi:/bin/bashzhangsan : x:1002:1006::/home/zhangsan:/bin/bash [root@lokott ~] # tail-5 / etc/group / / display group information printadmin:x:985:caiwu:x:1002:lisi:x:1003:wangwu:x:1005:zhangsan:x:1006: [root@lokott ~] # gpasswd-M lisi Zhangsan wangwu / / add two users to the wangwu group in batch [root@lokott ~] # tail-5 / etc/groupprintadmin:x:985:caiwu:x:1002:lisi:x:1003:wangwu:x:1005:lisi,zhangsan / / check the information zhangsan:x:1006: [root@lokott ~] # useradd hh / / add two new users To verify the coverage function of-M [root@lokott ~] # useradd ww [root@lokott ~] # gpasswd-M hh,ww wangwu [root@lokott ~] # tail-5 / etc/grouplisi:x:1003:wangwu:x:1005:hh,ww / / the original lisi and zhangsan are kicked out zhangsan:x:1006:hh:x:1007:ww:x:1004: delete-- groupdel group account

Attention! You cannot delete a group at will using the groupdel command. This command applies only to groups that are "not any user's initial group (primary group)". In other words, if a group is still a user's initial group (primary group), it cannot be deleted successfully using the groupdel command. For example:

[root@lokott] # tail-10 / etc/group stapdev:x:158:tcpdump:x:72:lokott:x:1000:printadmin:x:985:caiwu:x:1002:lisi:x:1003:wangwu:x:1005:hh Wwzhangsan:x:1006:hh:x:1007:ww:x:1004: [root@lokott ~] # groupdel caiwu [root@lokott ~] # groupdel lisigroupdel: the primary group of user "lisi" cannot be removed [root@lokott ~] # groupdel wangwu [root@lokott ~] # groupdel zhangsan groupdel: the primary group of user "zhangsan" [root@lokott ~] # groupdel hhgroupdel: the primary group of user "hh" [root@lokott ~] # groupdel wwgroupdel: the primary group of user "ww" [root@lokott ~] #

If you really want to delete, you can delete the initial member who created the group and then delete it.

[root@lokott note] # tail-1 / etc/passwdww:x:10000:10000::/home/ww:/bin/bash [root@lokott note] # groupdel wwgroupdel: cannot remove the primary group of user "ww" [root@lokott note] # userdel ww [root@lokott note] # tail-1 / etc/groupzhangsan:x:1006: [root@lokott note] # command lastb is used to view recently logged in information [root@lokott ~] # lastblisi: 1 1 Thu Oct 31 18:49-18:49 (00:00) root pts/1 Thu Oct 31 17:07-17:07 (00:00) root: 0:0 Thu Oct 24 14 root 43-14 root 43 (00) root: 0 Thu Oct 24 14:43-14:43 (00:00) root: 0:0 Thu Oct 24 14:43-14:43 (00:00) btmp begins Thu Oct 24 14:43:01 2019 [root@lokott] # IV. Permissions and attribution of files / directories 1. Access permission

Read r: allows you to view file contents and display directory lists

Write w: allows file contents to be modified, new files or subdirectories to be created, moved, or deleted in the directory

Executable x: allows you to run programs and change directories

two。 Ownership (ownership)

Owner: the user account used for this file or directory

Group: the group account used for this file or directory

3. Combined with an example, this paper introduces the total amount of authority [root@lokott] # ls-l. 1 root root 1785 October 23 12:21 anaconda-ks.cfg-rw-r--r--. 1 root root 1833 October 23 12:24 initial-setup-ks.cfgdrwxr-xr-x. 4 root root 73 October 30 22:03 note / / take this as an example

The following is about drwxr-xr-x. 4 root root 73 October 30 22:03 note to explain

D-file type (d for directory, l for linked file, c for character device (input / output) file, b block device (storage) file-ordinary file) rwx, rmurx, rmae x represent sovereign limits (here, readable, writable and executable), group permissions (here, readable and executable), Other permissions (in this case, readable and executable) 4-number of subdirectories first root-- owner

5. The second root-- belonging to group 73-- 22:03 on October 30-- creation time note-- directory name (file) 4. Set permissions for files and directories chmod command (- R recursion) chmod [ugoa] [+-=] [rwx] chmod nnn files or directories (preferred) / / the following is the permission operation for files [root@lokott note] # touch 2.sh [root@lokott note] # ls-l 2.sh / / 2.sh permission is 644Murray. 1 root root 0 October 31 21:41 2.sh [root@lokott note] # chmod uplix 2.sh [root@lokott note] # ls-l 2.sh-rwxr--r--. 1 root root 0 October 31 21:41 2.sh [root@lokott note] # chmod ugo+w 2.sh [root@lokott note] # ls-l 2.sh-rwxrw-rw-. 1 root root October 31 21:41 2.sh [root@lokott note] # chmod 655 2.sh [root@lokott note] # ls-l 2.sh-rw-r-xr-x. 1 root root October 31 21:41 2.sh// below is the permission operation on the directory [root@lokott note] # ll / / ll is the total amount of aliases for ls-l-color 8-rwxrwxrwx. 1 root root 0 October 31 21:40 1.txt-rw-r-xr-x. 1 root root 0 October 31 21:41 2.sh-rwxrwxrwx. 1 root root 286 October 30 22:03 ifcfg-ens33drwxrwxrwx. 2 root root 26 October 23 13:20 linux-cmd-rwxr-xr-x. 1 root root 30 October 30 22:02 readme.txtdrwxrwxrwx. 2 root root 173.Oct 30 21:56 shelldrwxr-xr-x. 2 root root 6 October 31 21:38 test [root@lokott note] # which ll alias ll='ls-l-color=auto' / usr/bin/ls [root@lokott note] # chmod 777 test/ change permission to 777 [root@lokott note] # ll total usage 8-rwxrwxrwx. 1 root root 0 October 31 21:40 1.txt-rw-r-xr-x. 1 root root 0 October 31 21:41 2.sh-rwxrwxrwx. 1 root root 286 October 30 22:03 ifcfg-ens33drwxrwxrwx. 2 root root 26 October 23 13:20 linux-cmd-rwxr-xr-x. 1 root root 30 October 30 22:02 readme.txtdrwxrwxrwx. 2 root root 173.Oct 30 21:56 shelldrwxrwxrwx. 2 root root 6 October 31 21:38 test [root@lokott note] # touch test/1.sh [root@lokott note] # ls-l test/1.sh-rw-r--r--. 1 root root October 31 21:50 the permissions of the test/1.sh / / directory have nothing to do with its subdirectories and file permissions unless recursively-R [root@lokott note] # chmod 777-R test/ recursively change permissions that is, all file permissions of test and its subdirectories are 777 [root@lokott note] # ls-l test/1.sh-rwxrwxrwx. 1 root root 0 October 31 21:50 test/1.sh

If you give subordinate groups and other users only write permission (622), you can force writes, but the original content will be overwritten!

[root@lokott test] # pwd / / the absolute path of the current directory / opt/test [root@lokott test] # ll / / displays the details of the total amount of 8 Murray Rafael. 1 root root 13 October 31 16:33 1.txt / / all user rights except root are read-only-rw--w--w-. 1 root root 18 October 31 18:33 2.txt / / the rest of the user rights except root are write-only [root@lokott test] # cat 1.txt tehsdahello [root@lokott test] # cat 2.txt / / the contents of the original 2.txt here are as follows: 2313542222244878 [root@lokott lisi] # su-lisi / / switch to lisi user's last login October 31 22:36:45 on CST 2019pts/1 [lisi@lokott ~] $cd / opt/test/ [lisi@lokott test] $ll / / No permission for ls ls: unable to open directory.: insufficient permissions [lisi@lokott test] $cat 1.txt / / indicates that you can view 1.txt content tehsdahello [lisi@lokott test] ] $vim 1.txt / / attempt to write data [lisi@lokott test] $cat 1.txt / / can wq! Forced save and exit, resulting in tehsdahellodadaasdaadas [lisi@lokott test] $cat 2.txtcat: 2.txt: insufficient permissions [lisi@lokott test] $vim 2.txt [lisi@lokott test] $cat 2.txt / / seems to be available after forced data writing, because the owner is lisi But if / / the owner is a root user, the lisi user cannot view ssdad dsawdad [lisi@lokott test] $ls-l 2.txtMurray RWM when the lisi user logs in. 1 lisi lisi 14 October 31 22:45 2.txt// uses the echo command to redirect and append data to the text [lisi@lokott test] $echo "123123" > 2.txt [lisi@lokott test] $cat 2.txt123123 [lisi@lokott test] $echo "123456" > > 2.txt [lisi@lokott test] $cat 2.txt123123123456 [lisi@lokott test] $su password: [root@lokott test] # ls-l Total usage 8Murray. 1 lisi lisi 27 October 31 22:43 1.txtMui RW Muhami. 1 lisi lisi 14 October 31 22:47 2.txt [root@lokott test] # cat 2.txt 123123123456 [root@lokott test] # 5. Set the attribution of files and directories to chownchown master chown: generic group chown master: generic group [root@lokott opt] # ls-l total dosage 0 Murray Rafael. 1 root root 0 October 31 16:19 demo01.txtdrwxr-xr-x. 2 root root 6 March 26 2015 rhdrwx-wx-wx. 2 root root 32 October 31 22:45 test [root@lokott opt] # chown lisi test [root@lokott opt] # ls-l total dosage 0Mel RW, RK, R, M, V, C, C, B, C, B. 2, root root 32, test [root@lokott opt] # chown lisi test [root@lokott opt] # ls-l 1 root root 0 October 31 16:19 demo01.txtdrwxr-xr-x. 2 root root 6 March 26 2015 rhdrwx-wx-wx. 2 lisi root 32 October 31 22:45 the owner of the test / / test directory itself becomes lisi, but the group has not changed [root@lokott opt] # chown root:lisi test [root@lokott opt] # ls-l total dosage 0Murray. 1 root root 0 October 31 16:19 demo01.txtdrwxr-xr-x. 2 root root 6 March 26 2015 rhdrwx-wx-wx. 2 root lisi 32 October 31 22:45 the owner of the test / / test directory itself becomes root and the group becomes chown [root @ root] # chown: root test [root@lokott opt] # ls-l the total amount is 0murr, Murray, Murray. 1 root root 0 October 31 16:19 demo01.txtdrwxr-xr-x. 2 root root 6 March 26 2015 rhdrwx-wx-wx. 2 root root 32 October 31 22:45 test / / test directory itself becomes root6. Permission mask umask

Function: control the permissions of newly created files or directories-note that they are only valid for newly created files or directories

The default permission to remove umask is

[root@lokott opt] # mkdir umasktest [root@lokott opt] # umask 000000 umasktest/ [root@lokott opt] # ll total consumption 0Murray RWM. 1 root root 0 October 31 16:19 demo01.txtdrwxr-xr-x. 2 root root 6 March 26 2015 rhdrwx-wx-wx. 2 root lisi 32 October 31 22:45 testdrwxrwxrwx. 2 root root 6 October 31 23:26 umasktest [root@lokott opt] # cd umasktest/ [root@lokott umasktest] # mkdir 2019 [root@lokott umasktest] # touch 1.txt [root@lokott umasktest] # ll total usage 0kyu RWFLY. 1 root root October 31 23:26 1.txt / / File permission is 666drwxrwxrwx. 2 root root 6 October 31 23:26 2019 / / the directory permissions are 777 [root@lokott umasktest] # cd. [root@lokott opt] # umask 111umasktest/ the original 1.txt and 2019 permissions have not changed! [root@lokott opt] # cd umasktest/ [root@lokott umasktest] # mkdir 2018 [root@lokott umasktest] # touch 2.txt [root@lokott umasktest] # ll total dosage 0 Murray RWMI. 1 root root 0Oct 31 23:26 1.txtdrwmuri rwwmuri. 2 root root 6 October 31 23:28 2018 / / the directory permission is 666drwxrwxrwx. 2 root root 6 October 31 23:26 2019 RW Murray RW Murray. 1 root root October 31 23:28 2.txt / / 2.txt permission is 666 [root@lokott umasktest] # cd.. [root@lokott opt] # umask 666 umasktest/ [root@lokott opt] # cd umasktest/ [root@lokott umasktest] # mkdir 2017 [root@lokott umasktest] # touch 3.txt [root@lokott umasktest] # ll total usage 0Murray RWMuir. 1 root root 0 October 31 23:26 1.txtd--x--x--x. 2 root root 6 October 31 23:29 2017 / / the directory permission is 111drwMurrwMurrwMel. 2 root root 6 October 31 23:28 2018drwxrwxrwx. 2 root root 6 October 31 23:26 2019 RW Murray RW Murray. 1 root root 0Oct 31 23:28 2.txtmuri. 1 root root October 31 23:29 3.txt / / File 3.txt permissions are all 0 [root@lokott umasktest] # umask / / View umask value 0666V, summary

It is mainly the introduction of account and rights management in Linux/Centos7, mainly the option of the command combined with the demonstration case of the operator needs to pay attention to many places that are inconsistent with the normal thinking, need to try more and try more!

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