6 Linux系统中目录结构知识

linux目录结构

[root@oldboyedu-01 ~]# tree -L 1 /
/
├── app
├── application
├── bin //命令，二进制文件的存放目录 binary
├── boot //系统引导程序+系统内核文件
├── dev //device 设备，光盘，硬盘
├── etc //存放系统的配置文件
├── home //普通用户的家目录，贫民窟
├── lib //libary库，库文件
├── lib64 //lib64 系统是64位库文件
├── lost+found //磁盘或者文件系统损坏，断电，临时文件位置
├── media //
├── mnt //临时的挂载点
├── opt //option第三方软件安装目录
├── proc //虚拟的目录，目录里的内容是内存中的信息（内核，进程，软件）
├── root //root 皇宫，root用户的家目录
├── sbin //super binary超级命令，只root用户能用命令
├── selinux //selinux及其配置文件存放的目录
├── srv
├── sys //虚拟的目录，内存信息
├── tmp //临时文件的存放位置，垃圾堆
├── usr //存放用户的程序
└── var //varible经常变换的文件，系统日志

//（一）
（1）.一切从根开始；一切皆文件！
（2）.linux设备（磁盘/光盘分区）不挂载则无法使用。
（3）.挂载相当于给磁盘/光盘分区开了个入口（挂载点，即目录）；通过入口，进入到磁盘/光盘分区中。
//举例linux下使用光盘
[root@oldboyedu-01 ~]# ll /dev/cdrom //1.光盘放入光驱；2.使用光盘，无法直接cat
lrwxrwxrwx. 1 root root 3 Dec 11 22:35 /dev/cdrom -> sr0

[root@oldboyedu-01 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 8.8G 1.5G 7.0G 17% /
tmpfs 1.9G 0 1.9G 0% /dev/shm
/dev/sda1 190M 40M 141M 22% /boot
[root@oldboyedu-01 ~]# mount /dev/cdrom /mnt/ //将光盘挂载到系统里。
mount: block device /dev/sr0 is write-protected, mounting read-only
[root@oldboyedu-01 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 8.8G 1.5G 7.0G 17% /
tmpfs 1.9G 0 1.9G 0% /dev/shm
/dev/sda1 190M 40M 141M 22% /boot
/dev/sr0 3.7G 3.7G 0 100% /mnt
[root@oldboyedu-01 ~]# cd /mnt/
[root@oldboyedu-01 mnt]# ls
CentOS_BuildTag GPL Packages RPM-GPG-KEY-CentOS-6 RPM-GPG-KEY-CentOS-Testing-6
EFI images RELEASE-NOTES-en-US.html RPM-GPG-KEY-CentOS-Debug-6 TRANS.TBL
EULA isolinux repodata RPM-GPG-KEY-CentOS-Security-6

[root@oldboyedu-01 ~]# su - oldboy
[oldboy@oldboyedu-01 ~]$ pwd
/home/oldboy
[oldboy@oldboyedu-01 ~]$

//（二）网卡配置文件
[root@oldboyedu-01 ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0 //网卡名字
HWADDR=00:0c:29:db:5d:02 //硬件地址，MAC地址（世界唯一）
TYPE=Ethernet //互联网类型
UUID=506cdc15-37ca-4674-b228-1eb03ca7f82b //UUID 系统中唯一的标识
ONBOOT=yes //重启时是否开启网卡
NM_CONTROLLED=yes //是否能被network软件进行管理
BOOTPROTO=none
//网卡获取IP地址的方式：
（1）none/static IP地址是固定的
（2）dhcp 自动获取IP地址
IPADDR=10.0.0.200 //IP地址
NETMASK=255.255.255.0 //子网掩码
GATEWAY=10.0.0.2 //网关，默认上网的出口
USERCTL=no //是否允许普通用户管理网卡：开，关，重启
PEERDNS=yes
IPV6INIT=no

上网使用www.baidu.com jd.com taobao.com 域名
DNS:域名解析服务，将使用的域名解析（转化）为IP地址。
阿里云：223.5.5.5 223.6.6.6
114:114.114.114.114
谷歌：8.8.8.8

//DNS未设置相关的错误
[root@oldboyedu-01 mnt]# yum install tree
Loaded plugins: fastestmirror, security
Setting up Install Process
Loading mirror speeds from cached hostfile
Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=6&arch=x86_64&repo=os&infra=stock error was
14: PYCURL ERROR 6 - "Couldn't resolve host 'mirrorlist.centos.org'"
Error: Cannot find a valid baseurl for repo: base

[root@oldboyedu-01 ~]# ping baidu.com //1.是否能上网；报错
ping: unknown host baidu.com
[root@oldboyedu-01 ~]# ping 223.5.5.5 //2.DNS是否有问题；能ping通
PING 223.5.5.5 (223.5.5.5) 56(84) bytes of data.
64 bytes from 223.5.5.5: icmp_seq=1 ttl=128 time=39.6 ms
64 bytes from 223.5.5.5: icmp_seq=2 ttl=128 time=36.3 ms
^C
1.2==>证明DNS有问题！

//解决方法：
1.修改DNS，在网卡配置文件中添加：
DNS1=223.5.5.5
DNS2=223.6.6.6
2.重启网卡以配置生效：
[root@oldboyedu-01 ~]# ifdown eth0 && ifup eth0 //重启某个网卡
Determining if ip address 10.0.0.200 is already in use for device eth0...
[root@oldboyedu-01 ~]# /etc/init.d/network restart //重启所有网卡
Shutting down interface eth0: [ OK ]
Shutting down loopback interface: [ OK ]
Bringing up loopback interface: [ OK ]
Bringing up interface eth0: Determining if ip address 10.0.0.200 is already in use for device eth0...
[ OK ]
（三）网卡配置文件 优先于该 DNS配置文件 [root@oldboyedu-01 ~]# cat /etc/resolv.conf
nameserver 223.5.5.5
nameserver 223.6.6.6
[root@oldboyedu-01 ~]# vim /etc/resolv.conf
[root@oldboyedu-01 ~]# cat /etc/resolv.conf //修改
nameserver 8.8.8.8
nameserver 114.114.114.114
[root@oldboyedu-01 ~]# /etc/init.d/network restart
Shutting down interface eth0: [ OK ]
Shutting down loopback interface: [ OK ]
Bringing up loopback interface: [ OK ]
Bringing up interface eth0: Determining if ip address 10.0.0.200 is already in use for device eth0...
[ OK ]
[root@oldboyedu-01 ~]# cat /etc/resolv.conf //恢复了！
nameserver 223.5.5.5
nameserver 223.6.6.6

//（四）IP地址与域名解析关系，对主机名进行解析
[root@oldboyedu-01 ~]# cat /etc/hosts
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6

www.baidu.com == 61.135.169.125
//想办法将www.baidu.com www.jd.com解析到10.0.0.200（测试机）
[root@oldboyedu-01 ~]# cat /etc/hosts
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
10.0.0.200 www.baidu.com www.jd.com
[root@oldboyedu-01 ~]# ping www.baidu.com
PING www.baidu.com (10.0.0.200) 56(84) bytes of data.
64 bytes from www.baidu.com (10.0.0.200): icmp_seq=1 ttl=64 time=0.033 ms
64 bytes from www.baidu.com (10.0.0.200): icmp_seq=2 ttl=64 time=0.067 ms
^C
--- www.baidu.com ping statistics ---
--------------------------------------------------
问题解决：
我这里用不了阿里云的dns 换成114的就行了。
还有虚拟机网卡有些问题。
8.8.8.8是移动自己搞的，不是真的谷歌。
是的 还是没啥通用的。
具体工作的时候 机房会有对应的DNS的。

[root@oldboyedu-01 ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
HWADDR=00:0c:29:db:5d:02
TYPE=Ethernet
UUID=506cdc15-37ca-4674-b228-1eb03ca7f82b
ONBOOT=yes
NM_CONTROLLED=yes
BOOTPROTO=none
IPADDR=10.0.0.200
NETMASK=255.255.255.0
GATEWAY=10.0.0.2
USERCTL=no
PEERDNS=yes
IPV6INIT=no
DNS1=114.114.114.114
DNS2=114.114.115.115
[root@oldboyedu-01 ~]# cat /etc/resolv.conf //接着变化而已
nameserver 114.114.114.114
nameserver 114.114.115.115
[root@oldboyedu-01 ~]# yum install -y tree
Loaded plugins: fastestmirror, security
Setting up Install Process
Loading mirror speeds from cached hostfile
* base: centos.ustc.edu.cn
* extras: mirrors.neusoft.edu.cn
* updates: mirrors.sohu.com
Package tree-1.5.3-3.el6.x86_64 already installed and latest version
Nothing to do
[root@oldboyedu-01 ~]# rpm -qa |grep tree //检查是否安装该软件
tree-1.5.3-3.el6.x86_64

测试：
[root@oldboyedu-01 ~]# ping www.baidu.com
PING www.a.shifen.com (183.232.231.172) 56(84) bytes of data.
64 bytes from 183.232.231.172: icmp_seq=1 ttl=128 time=34.3 ms
64 bytes from 183.232.231.172: icmp_seq=2 ttl=128 time=34.5 ms
^C
--- www.a.shifen.com ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1467ms
rtt min/avg/max/mdev = 34.388/34.488/34.589/0.211 ms
[root@oldboyedu-01 ~]# ping 114.114.114.114
PING 114.114.114.114 (114.114.114.114) 56(84) bytes of data.
64 bytes from 114.114.114.114: icmp_seq=1 ttl=128 time=33.2 ms
64 bytes from 114.114.114.114: icmp_seq=2 ttl=128 time=33.6 ms
^C
--- 114.114.114.114 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1378ms
rtt min/avg/max/mdev = 33.275/33.455/33.636/0.256 ms
[root@oldboyedu-01 ~]# ping 114.114.115.115
PING 114.114.115.115 (114.114.115.115) 56(84) bytes of data.
64 bytes from 114.114.115.115: icmp_seq=1 ttl=128 time=31.9 ms
64 bytes from 114.114.115.115: icmp_seq=2 ttl=128 time=31.5 ms
^C
--- 114.114.115.115 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1288ms
rtt min/avg/max/mdev = 31.529/31.736/31.944/0.273 ms
--------------------------------------------------
//（五）修改主机名的文件
[root@crmn ~]# cat /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=oldboyedu-01 //永久修改，重启生效

[root@oldboyedu-01 ~]# hostname crmn //临时修改，重启失效
[root@oldboyedu-01 ~]# hostname //查看当前主机名
crmn
......logout......
Last login: Tue Dec 12 04:15:58 2017 from 10.0.0.1
[root@crmn ~]#
//Esc+. 使用上一个命令的后部分。

//（六）开机时自动挂载的文件，开机时给每个磁盘分区开一个入口。
[root@oldboyedu-01 ~]# cat /etc/fstab
#
# /etc/fstab
# Created by anaconda on Mon Dec 11 22:09:00 2017
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=c059106b-d931-4598-874d-3cb76f48cd7e / ext4 defaults 1 1
UUID=6f882027-3dff-4071-85e6-5e15024b5a89 /boot ext4 defaults 1 2
UUID=cf1accb4-dd1a-4c7b-9ccb-4ae500fcdd50 swap swap defaults 0 0
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
//表示设备/分区 //表示入口/目录/挂载点
[root@oldboyedu-01 ~]# df -h //显示磁盘的使用情况，-h人类可读
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 8.8G 3.4G 5.0G 41% /
tmpfs 1.9G 0 1.9G 0% /dev/shm
/dev/sda1 190M 40M 141M 22% /boot
[root@oldboyedu-01 ~]# blkid
/dev/sda3: UUID="c059106b-d931-4598-874d-3cb76f48cd7e" TYPE="ext4"
/dev/sda1: UUID="6f882027-3dff-4071-85e6-5e15024b5a89" TYPE="ext4"
/dev/sda2: UUID="cf1accb4-dd1a-4c7b-9ccb-4ae500fcdd50" TYPE="swap"

//（七）开机时自动运行的文件，需要开机自启动的软件/命令/服务放在该文件中。
[root@oldboyedu-01 ~]# cat /etc/rc.local
#!/bin/sh
#
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.
touch /var/lock/subsys/local
//如何让一个软件/命令/服务开机自启动？
（1）/etc/rc.local 服务器运行软件清单
（2）chkconfig管理 开机自启动

//（八）开机时运行级别的配置文件
[root@oldboyedu-01 ~]# cat /etc/inittab //init tab(table)
# Default runlevel. The runlevels used are:
# 0 - halt (Do NOT set initdefault to this) //关机状态，不要将运行级别设置为0
# 1 - Single user mode //单用户模式，root密码忘记了
# 2 - Multiuser, without NFS (The same as 3, if you do not have networking) //多用户模式，没有NFS
# 3 - Full multiuser mode //完全的多用户模式，命令模式，文本模式
# 4 - unused //未使用
# 5 - X11 //X11，桌面模式，图形化界面模式
# 6 - reboot (Do NOT set initdefault to this) //重启模式
#
id:3:initdefault: //修改后永久切换运行级别，重启生效
[root@oldboyedu-01 ~]# runlevel //查看运行级别
N 3
//上次使用的运行级别 当前系统的运行级别

[root@oldboyedu-01 ~]# init 5^C //临时切换运行级别
[root@oldboyedu-01 ~]# runlevel
N 3

[root@oldboyedu-01 ~]# cat /etc/init.d/ //服务管理的命令
//系统环境生效
[root@oldboyedu-01 ~]# cat /etc/profile //系统环境变量、别名 eg:PS1,PATH;LANG==>/etc/sysconfig/i18n
[root@oldboyedu-01 ~]# cat /etc/bashrc //别名
//当前用户生效
[root@oldboyedu-01 ~]# cat ~/.bashrc
[root@oldboyedu-01 ~]# cat ~/.bash_profile

[root@oldboyedu-01 ~]# ls /usr/local/ //编译安装的软件默认的位置
bin doc etc games include lib lib64 libexec man sbin share src

//linux下安装软件方式：
（1）yum 自动解决安装依赖的软件，eg:点外卖，缺啥都给你解决
（2）rpm 缺啥少啥自己解决，eg:速冻水饺
（3）编译安装 ./configure; make; make install eg:自己做饭

[root@oldboyedu-01 ~]# tail -1 /var/log/messages //系统默认日志
Dec 12 09:06:15 oldboyedu-01 yum[3521]: Installed: tree-1.5.3-3.el6.x86_64
[root@oldboyedu-01 ~]# tail -2 /var/log/secure //系统用户的登录信息（谁，何时，从哪里登录，成功与否）
Dec 12 09:23:24 oldboyedu-01 groupadd[12982]: group added to /etc/group: name=mysql, GID=501
Dec 12 09:23:24 oldboyedu-01 groupadd[12982]: group added to /etc/gshadow: name=mysql

[root@oldboyedu-01 ~]# cat /proc/meminfo //查看内存信息
[root@oldboyedu-01 ~]# free -h //显示当前内存占用（使用）情况
total used free shared buffers cached
Mem: 3.7G 2.4G 1.3G 228K 37M 2.1G
-/+ buffers/cache: 260M 3.5G
Swap: 767M 0B 767M
[root@oldboyedu-01 ~]# cat /proc/cpuinfo //查看cpu信息
[root@oldboyedu-01 ~]# lscpu

[root@oldboyedu-01 ~]# cat /proc/loadavg //查看系统的负载
0.00 0.00 0.00 1/179 25422
[root@oldboyedu-01 ~]# w
11:27:32 up 3:06, 3 users, load average: 0.00, 0.00, 0.00
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
root tty1 - 08:39 2:45m 0.00s 0.00s -bash
root pts/4 10.0.0.1 09:00 1:39m 6.53s 0.40s -bash
root pts/5 10.0.0.1 09:51 1.00s 1.08s 0.27s w
//负载：系统的繁忙程度
最近1分钟，最近5分钟，最近15分钟 平均负载
系统的负载接近系统CPU的核心数量

[root@oldboyedu-01 ~]# cat /proc/mounts //显示系统的挂载信息
rootfs / rootfs rw 0 0
proc /proc proc rw,relatime 0 0
sysfs /sys sysfs rw,relatime 0 0
devtmpfs /dev devtmpfs rw,relatime,size=1939616k,nr_inodes=484904,mode=755 0 0
devpts /dev/pts devpts rw,relatime,gid=5,mode=620,ptmxmode=000 0 0
tmpfs /dev/shm tmpfs rw,relatime 0 0
/dev/sda3 / ext4 rw,relatime,barrier=1,data=ordered 0 0
/proc/bus/usb /proc/bus/usb usbfs rw,relatime 0 0
/dev/sda1 /boot ext4 rw,relatime,barrier=1,data=ordered 0 0
none /proc/sys/fs/binfmt_misc binfmt_misc rw,relatime 0 0
[root@oldboyedu-01 ~]# df -h //常用
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 8.8G 3.4G 5.0G 41% /
tmpfs 1.9G 0 1.9G 0% /dev/shm
/dev/sda1 190M 40M 141M 22% /boot
[root@oldboyedu-01 ~]# findmnt //罕用
TARGET SOURCE FSTYPE OPTIONS
/ /dev/sda3 ext4 rw,relatime,barrier=1,data=ordered
├─/proc proc proc rw,relatime
│ ├─/proc/bus/usb /proc/bus/usb usbfs rw,relatime
│ └─/proc/sys/fs/binfmt_misc binfmt_misc rw,relatime
├─/sys sysfs sysfs rw,relatime
├─/dev devtmpfs devtmpfs rw,relatime,size=1939616k,nr_inodes=484904,mode=755
│ ├─/dev/pts devpts devpts rw,relatime,gid=5,mode=620,ptmxmode=000
│ └─/dev/shm tmpfs tmpfs rw,relatime
└─/boot /dev/sda1 ext4 rw,relatime,barrier=1,data=ordered