· learnings · 3 min read
Linux学习日志 Ⅱ
帐户建立
建立组:
Groupadd –g
组建立之后存放在/etc/group里面, 显示出来为:
Group Name: x: Group ID
建立用户:
Useradd –u
Ex.
Useradd –u 1000 –g 751 –d /home/yoh –s /bin/bash –c “yoh” yoh
用户建立之后存放在/etc/passwd里面,显示出来为:
username:x:uid:gid:full-name:home-directory:default-shell
Examples:
n1234567:x:500:600:John Black:/home/n1234567:/bin/bash
建立密码:
Passwd
查看密码:(显示为x的部分)
用root用户进入到目录/etc/shadow, 显示出来为:
用户名:密码:最后更改时间:更改间隔时间:下次更改日期:离更改多少日期警告用户:expire后多少日期被注销:账户使用期限:保留字段
察看用户信息:
Finger
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lower IDs (below 500) reserved for system users
Root user has numeric user ID of 0
标准目录结构:
–/bin and /usr/bin store user executable programs
–/sbin and /usr/sbin store system executable programs
–/tmp contains temporary files
–/etc contains configuration files
–/var contains log files, spool files
–/dev Device Files
Block devices read and write blocks of data at a time
eg floppy drives, hard disks
eg device files - /dev/fd0, /dev/hda
Character devices read and write one character at a time
eg printers, terminals
eg device files - /dev/lp0, /dev/tty2
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账户管理
更改权限
“chown”, “chgrp”, “chmod”
●“chown” changes owning user of file or directory
●“chgrp” changes owning group of file or directory
Chgrp
or
Chown user:group
chmod 0740
“chmod u=rwx,g=r
Suspend user account:
passwd –l
Full delete user account
userdel –f –r
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Format of listing includes
type owner group other
d/c/b/l rwx rwx rwx
Types of files include
–d: directory, c: character device, b: block device, l: symbolic link
●SetUID/SetGID
–Executes with rights of owner/owning group, instead of executor
●Sticky Bit
–Only owner of file, owner of directory, or root user can delete files within
Special Permissions
●If owner field has “s” in place of “x”, then SetUID executable
●If group field has “s” in place of “x”, then SetGID executable
●If other field has “t” in place of “x”, then sticky
●Permissions can be written as 4 octal digits
●First digit in binary:
–SetUID SetGID Sticky
●Remaining 3 digits in binary correspond to Owner, Group and Other permissions
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Shell Scripts + 定义显示
Vi filename
#! /bin/bash 所在shell
head –n 1 /etc/passwd 显示开头第一行
tail –n 2 /etc/passwd 显示末尾两行
wc –l /etc/passwd 统计行数
grep –w student 显示有student的文件
>sortedlist 输出到文件
执行script文件
If executable, type in name of script, if in $PATH
–If not in path, type “./
If not executable, use eg “sh” command
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Regular Expression Symbols
●. matches any character
lecture.. The word “lecture” followed by any 2 characters
●^ start of line
^The A line starting with the word “The”
●$ end of line
end$ A line ending with the word “end”
●[ ] one of the enclosed characters
lecture[123] lecture1 lecture2 or lecture3 match this
“ls > outfile”
–runs “ls” and redirects all the output from “ls” to the file “outfile”
“ls | wc”
–runs “ls” and redirects all the output from “ls” to be input to “wc”
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安装卸载程序
●Install
–# rpm -i
●Update
–# rpm -u
●Query
–# rpm -q
Need to solve:
1. chmod 0740
answer: setUID 4, SetGID 2, Sticky 1