拾遗：Linux 用户及权限管理基础

Lacks of Knowledge 1:

　　Linux has large amount of COMMANDS,but many of them have similar funtions,it's annoying! So,how to get the highest efficiency in a very limited period?

　　Choise only one method which cat solve your problem[s] perfectly,and throw others away!

　　Just as the command "history",I will never waste my time on "!xxx","!<",etc. Because "history | grep" will solve any problems as all the others can do.

　　It's same for me to deal with the chapter of user-management.I will only focus on the formats of four files(/etc/passwd,/etc/shadow/,/etc/group,/etc/gshadow) and three necessary commands("useradd","newusers","chpasswd").

　　These seven tools are enough,as below:

f@z ~ $ cat /etc/passwd

qemu:x:77:77:added by portage for libvirt:/dev/null:/sbin/nologin

ldap:x:439:439:added by portage for openldap:/usr/lib64/openldap:/sbin/nologin

name:password:UID:GID:unnecessary comments of user:home directory:shell

z f # cat /etc/shadow

root:$6$QJnD:17015:0:99999:7:::

f:$6$5ajHHo.:17015:0:99999:7:::

name:password:date of last password change:minimun password age[days]:maximum password age[days]:password warning period[days]:password inactivity period[days]:account expiration date

Note:the third and eighth object(date of last password change,account expiration date) is expressed as the number of days since Jan 1, 1970.

z f # cat /etc/group

root:x:0:root

bin:x:1:root,bin,daemon

group name:password:GID:member[s] of the group

z f # cat /etc/gshadow

root:::root

bin:::root,bin,daemon

group name:password:administrator[s] of the group:member[s] of the group

newusers　　:#recive arguments from file,format same as /etc/passwd

[root@ fh]# cat testfile

zhangsan:abc:::xxxx:/home/zhangsan:/bin/bash

lisi:abc:::xxxx:/home/lisi:/bin/bash

[root@ fh]# newusers testfile

[root@ fh]# tail -n  /etc/passwd

zhangsan:x:::xxxx:/home/zhangsan:/bin/bash

lisi:x:::xxxx:/home/lisi:/bin/bash

chpasswd　　:#recive arguments from stdin

[root@ fh]# cat testfile2

zhangsan:catdog

lisi:dogcat

[root@ fh]# cat testfile2 | chpasswd

[fh@ ~]$ su - zhangsan

Password:

-bash-4.2$

useradd -G -s -m -k

[root@ fh]# useradd -m -G wheel -s /bin/bash -k /dev/null test_user

[root@ fh]# tail -n  /etc/passwd

test_user:x::::/home/test_user:/bin/bash

[root@ fh]# grep 'wheel' /etc/group

wheel:x::fh,test_user

[root@ fh]# ls -a /home/test_user/

.  ..

Lacks of Knowledge 2:

setfacl -M　　:#revice arguments from file

[root@ fh]# cat file1

u:fh:

g:fh:

d:u:fh:rx

mask::

[root@ fh]# setfacl -M file1 a_dir/

[root@ fh]# getfacl a_dir/

# file: a_dir/

# owner: root

# group: root

user::rwx

user:fh:rw-            #effective:r--

group::r-x

group:fh:r--

mask::r-x

other::r-x

default:user::rwx

default:user:fh:r-x

default:group::r-x

default:mask::r-x

default:other::r-x

巴特西

拾遗：Linux 用户及权限管理基础

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