笔记八

Posted 2020-08-20

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#############第十单元.selinux的初级管理##################

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1.什么时selinux

selinux，内核级加强型防火墙

2.如何管理selinux级别

selinux开启或者关闭）

vim /etc/sysconfig/selinux

selinux=disabled ##关闭状态

selinux=Enforcing ##强制状态

selinux=Permissive ##警告状态

getenforce ##查看状态

当selinux开启时

setenforce 0|1 ##更改selinux运行级别

3.如何更改文件安全上下文(标签)

如果文件的安全上下文与服务不匹配，则看不到文件

临时更改）

chcon -t 安全上下文文件

chcon -t public_content_t /publicftp -R

实例:

[[email protected] mnt]# chcon -t public_content_t /var/ftp/pub/ -R

永久更改）

semanage fcontext -l ##列出内核安全上下文列表内容

semanage fcontext -a -t public_content_t ‘/publicftp(/.*)?‘

restorecon -FvvR /publicftp/

实例:

做此实验时，接上面

[[email protected] ~]# lftp 172.25.7.11

lftp 172.25.7.11:~> ls

lftp 172.25.7.11:/> ls

lftp 172.25.7.11:/> quit

[[email protected] ~]# semanage fcontext -a -t public_content_t ‘/ftpdir(/.*)?‘

[[email protected] ~]# semanage fcontext -l | grep ftpdir

/ftpdir(/.*)? all files system_u:object_r:public_content_t:s0

/tftpboot directory system_u:object_r:tftpdir_t:s0

/tftpboot/.* all files system_u:object_r:tftpdir_t:s0

/var/lib/tftpboot(/.*)? all files system_u:object_r:tftpdir_rw_t:s0

[[email protected] ~]# lftp 172.25.7.11

lftp 172.25.7.11:~> ls

lftp 172.25.7.11:/> quit

[[email protected] ~]# restorecon -RvvF /ftpdir/

restorecon reset /ftpdir/lzt3/lzt3file context system_u:object_r:default_t:s0->system_u:object_r:public_content_t:s0

[[email protected] ~]# lftp 172.25.7.11

lftp 172.25.7.11:~> ls

drwxr-xr-x 3 0 0 29 Nov 19 01:25 lzt1

drwxr-xr-x 3 0 0 29 Nov 19 01:34 lzt2

drwxr-xr-x 2 0 0 21 Nov 13 07:44 lzt3

lftp 172.25.7.11:/> quit

4.如何控制selinux对服务功能的开关

getsebool -a | grep 服务名称

getsebool -a | grep ftp

setsebool -P 功能bool值 on|off

setsebool -P ftpd_anon_write on ##此处-P表示永久性，注意P为大写

chcon -t public_content_rw_t /var/ftp/pub/ ##修改/var/ftp/pub的标签为public_content_rw_t(rw表示可写)

实例:

[[email protected] ~]# lftp 172.25.7.11

lftp 172.25.7.11:~> ls

drwxrwxr-x 2 0 50 17 Nov 19 02:55 pub

lftp 172.25.7.11:/> cd pub/

lftp 172.25.7.11:/pub> ls

-rw-r--r-- 1 0 0 0 Nov 19 02:55 file

lftp 172.25.7.11:/pub> put /etc/passwd

put: Access failed: 553 Could not create file. (passwd)

lftp 172.25.7.11:/pub> quit

[[email protected] ~]# chcon -t public_content_rw_t /var/ftp/pub

[[email protected] ~]# lftp 172.25.7.11

lftp 172.25.7.11:~> ls

drwxrwxr-x 2 0 50 17 Nov 19 02:55 pub

lftp 172.25.7.11:/> cd pub/

lftp 172.25.7.11:/pub> ls

-rw-r--r-- 1 0 0 0 Nov 19 02:55 file

lftp 172.25.7.11:/pub> put /etc/passwd

put: Access failed: 553 Could not create file. (passwd)

lftp 172.25.7.11:/pub> quit

[[email protected] ~]# setenforce 0 ##将selinux设置成为警告模式

[[email protected] ~]# lftp 172.25.7.11

lftp 172.25.7.11:~> cd pub/

lftp 172.25.7.11:/pub> put /etc/passwd

2079 bytes transferred

lftp 172.25.7.11:/pub> quit

[[email protected] ~]# getsebool -a | grep ftp

ftp_home_dir --> off

ftpd_anon_write --> off

ftpd_connect_all_unreserved --> off

ftpd_connect_db --> off

ftpd_full_access --> off

[[email protected] ~]# setsebool -P ftpd_anon_write on

[[email protected] ~]# getsebool -a | grep ftp

ftp_home_dir --> off

ftpd_anon_write --> on

ftpd_connect_all_unreserved --> off

ftpd_connect_db --> off

ftpd_full_access --> off

[[email protected] ~]# lftp 172.25.7.11

lftp 172.25.7.11:~> ls

drwxrwxr-x 2 0 50 30 Nov 19 03:40 pub

lftp 172.25.7.11:/pub> put /etc/group

874 bytes transferred

lftp 172.25.7.11:/pub> ls

-rw-r--r-- 1 0 0 0 Nov 19 02:55 file

-rw------- 1 14 50 874 Nov 19 03:49 group

-rw------- 1 14 50 2079 Nov 19 03:40 passwd

lftp 172.25.7.11:/pub> quit

5.监控selinux的错误信息

setroubleshoot-server

#########################################

##############第十一单元.系统恢复########

#########################################

1.系统启动流程

通电

bios(主板上的只读存储中，basic input or output system)

作用，硬件检测，激活硬件

grub系统引导（grub引导分为两个阶段）

1）阶段1 mbr（主引导记录）主引导记录在硬盘上的0磁道，一扇区，446个字节

*）dd if=/dev/zero of=/dev/vda bs=446 count=1 可以清空mbr

*）进入到挽救模式，执行chroot /mnt/sysimage切换到真实/环境，

并执行grub2-install /dev/vda

然后执行两次exit

再选择从硬盘启动

2）阶段2 grub文件引导阶段

找到/boot分区

读取/boot/grub2/grub.cfg

文件丢失，没有重启之前，执行:grub2-mkconfig >/boot/grub2/grub.cfg

@@@!!! 情况一(trouble test2,trouble test3的第二步):删除了/boot/grub2/grub.cfg 即，执行 rm -fr /boot/grub2/grub.cfg

(若执行了reboot，则,选择从网卡或者光盘启动，然后执行:

grub> set root=‘hd0,msdos1‘

grub> linux16 /boot/vmlinuz-3.10.0-123. el7.x86_64 ro root=/dev/vda1

grub> initrd16 /boot/initramfs-3.10.0-123.el7.x86_64.img

grub> boot

然后选择从硬盘启动

)

启动内核，只读挂载/设备

检测设备

对设备驱动进行初始化

进入系统初始化阶段

内核丢失，从新安装内核安装包就可以解决

rpm -ivh kernel-xxxxx.rpm --force

@@@!!!情况二(trouble test3的第一步): 删除了/boot/vmlinuz-3.10.0-123. el7.x86_64

(若执行了reboot，则,选择从网卡或者光盘启动，然后执行:

bash-4.2# chroot /mnt/sysimage

bash-4.2# cd /mnt

bash-4.2# lftp 172.25.254.250

lftp 172.25.254.250:/> cd pub/rhel7.0/Packages

lftp 172.25.254.250: cd pub/rhel7.0/Packages/> get kernel-3.10.0-123.el7.x86_64.rpm

lftp 172.25.254.250: cd pub/rhel7.0/Packages/> quit

bash-4.2# rpm2cpio kernel-3.10.0-123.el7.x86_64.rpm | cpio -id

bash-4.2# cd boot/

bash-4.2# cp vmlinuz-3.10.0-123. el7.x86_64 /boot

bash-4.2# exit

然后选择从硬盘启动

)

系统初始化阶段

系统初始化阶段加载initrd镜像

开启初始化进程systemd

开始selinux

加载内核参数

初始化系统时钟，键盘，主机名称

重新读写挂载/设备

激活raid，lvm

激活配额

启动multi-user.target.wants中的所有服务

服务列表:

runlever0.target -> poweroff.target

runlever1.target -> rescue.target

runlever2.target -> multi-user.target

runlever3.target -> multi-user.target

runlever4.target -> multi-user.target

runlever5.target -> grapical.target

runlever6.target -> reboot.target

设定启动级别

systemctl set-default + 启动级别

/etc/systemd/system/default.target

@@重启示例(trouble test6):

[[email protected] ~]# rm -fr /etc/systemd/system/default.target

[[email protected] ~]# ln -s /usr/lib/systemd/system/reboot.target /etc/systemd/system/default.target

[[email protected] ~]# reboot

(在进入到默认启动页面时，按‘e’进入编辑页面，只修改

linux16 /boot/vmlinuz-3.10.0-123.el7.x86_64 root=UUID=9bf...-848e-..883d1 rw rd.break 然后按‘ctrl+x‘进入新的编辑环境

switch_root:/# chroot /sysroot/

sh-4.2# rm -fr /etc/systemd/system/default.target

sh-4.2# ln -s /usr/lib/systemd/system/graphical.target /etc/systemd/system/default.target

sh-4.2# exit

switch_root:/# exit 接着会继续进入启动页面，虚拟机启动

)

开启虚拟控制台

启动图形

initramfs-`uname -r`.img的使用：

mkinitrd /boot/initramfs-`uname -r`.img `uname -r` 或

mkinitrd /boot/initramfs-$(uname -r).img $(uname -r) 进行恢复

@@@!!!情况三:删除了/boot/initramfs-3.10.0-123.el7.x86_64.img 即，rm -fr /boot/initramfs-3.10.0-123.el7.x86_64.img

(然后执行 reboot,选择从网卡或光盘启动:

bash-4.2# chroot /mnt/sysimage

bash-4.2# cd /boot/

bash-4.2# mkinitrd /boot/initramfs-$(uname -r).img $(uname -r)

bash-4.2# exit

然后选择从硬盘启动

)

@@@!!!情况四(trouble test4):删除了/boot分区，即，rm -fr /boot

(然后执行reboot，选择从网卡或光盘启动:

bash-4.2# chroot /mnt/sysimage/

bash-4.2# cd /boot/

bash-4.2# ls

bash-4.2# mkinitrd /boot/initramfs-$(uname -r).img $(uname -r)

bash-4.2# cd /boot/

bash-4.2# grub2-install /dev/vda

bash-4.2# cd grub2/

bash-4.2# ls

bash-4.2# cd /

bash-4.2# rpm -ivh kernel-3.10.0-123.el7.x86_64.rpm --force

bash-4.2# cd /boot/grub2

bash-4.2# grub2-mkconfig > grub.cfg

bash-4.2# exit

然后选择从硬盘启动)

@@@!!!注意:如若rpm的数据库发生错误，则，执行:

bash-4.2# cd /var/lib/rpm

bash-4.2# rm -fr _*

bash-4.2# rpmdb --rebuilddb

然后接着执行:rpm -ivh kernel-3.10.0-123.el7.x86_64.rpm --force 直至结束)

修改了超级用户密码(忘记)/忘记超级用户密码,重启后:

(在进入到默认启动页面时，按‘e’进入编辑页面，只修改

linux16 /boot/vmlinuz-3.10.0-123.el7.x86_64 root=UUID=9bf...-848e-..883d1 rw rd.break 然后按‘ctrl+x‘进入新的编辑环境

switch_root:/# chroot /sysroot/

bash-4.2# passwd ##修改新密码

bash-4.2# touch /.autorelabel ##/.autorelabel此文件是让selinux重新读取已加载过的配置文件

bash-4.2# exit

switch_root:/# exit

)

下载trouble.rpm包:

然后执行:

ipm -ivh trouble-1.0-1.el7.x86_64.rpm

执行完后就可以使用trouble命令了。

例如: trouble test2

trouble练习:

@@test1:

(在进入到默认启动页面时，按‘e’进入编辑页面，只修改

linux16 /boot/vmlinuz-3.10.0-123.el7.x86_64 root=UUID=9bf...-848e-..883d1 rw rd.break 然后按‘ctrl+x‘进入新的编辑环境

switch_root:/# chroot /sysroot/

bash-4.2# passwd ##修改新密码

bash-4.2# touch /.autorelabel ##/.autorelabel此文件是让selinux重新读取已加载过的配置文件

bash-4.2# exit

switch_root:/# exit

)

@@test2:

(选择从网卡或者光盘启动，然后执行:

grub> set root=‘hd0,msdos1‘

grub> linux16 /boot/vmlinuz-3.10.0-123. el7.x86_64 ro root=/dev/vda1

grub> initrd16 /boot/initramfs-3.10.0-123.el7.x86_64.img

grub> boot

然后选择从硬盘启动

)

@@test3:

第一步 (选择从网卡或者光盘启动，然后执行:

bash-4.2# chroot /mnt/sysimage

bash-4.2# cd /mnt

bash-4.2# rpm2cpio kernel-3.10.0-123.el7.x86_64.rpm | cpio -id

bash-4.2# cd boot/

bash-4.2# cp vmlinuz-3.10.0-123. el7.x86_64 /boot

bash-4.2# exit

然后选择从硬盘启动

第二步

grub> set root=‘hd0,msdos1‘

grub> linux16 /boot/vmlinuz-3.10.0-123. el7.x86_64 ro root=/dev/vda1

grub> initrd16 /boot/initramfs-3.10.0-123.el7.x86_64.img

grub> boot

)

@@test4:

(选择从网卡或光盘启动:

bash-4.2# chroot /mnt/sysimage/

bash-4.2# cd /boot/

bash-4.2# ls

bash-4.2# mkinitrd /boot/initramfs-$(uname -r).img $(uname -r)

bash-4.2# cd /boot/

bash-4.2# grub2-install /dev/vda

bash-4.2# cd grub2/

bash-4.2# ls

bash-4.2# cd /

bash-4.2# rpm -ivh kernel-3.10.0-123.el7.x86_64.rpm --force

bash-4.2# cd /boot/grub2

bash-4.2# grub2-mkconfig > grub.cfg

bash-4.2# exit

然后选择从硬盘启动)

@@test5:

(选择从网卡或光盘启动:

sh-4.2# chroot /mnt/sysimage/

报错信息:failed to run command /bin/bash:No such file or dirrectory

sh-4.2# cp /bin/bash /mnt/sysimage/bin/bash

sh-4.2# boot

然后选择从硬盘启动)

@@test6:

(在进入到默认启动页面时，按‘e’进入编辑页面，只修改

linux16 /boot/vmlinuz-3.10.0-123.el7.x86_64 root=UUID=9bf...-848e-..883d1 rw rd.break 然后按‘ctrl+x‘进入新的编辑环境

switch_root:/# chroot /sysroot/

sh-4.2# rm -fr /etc/systemd/system/default.target

sh-4.2# ln -s /usr/lib/systemd/system/graphical.target /etc/systemd/system/default.target

sh-4.2# exit

switch_root:/# exit 接着会继续进入启动页面，虚拟机启动

)

#############dns高速缓存#########

第一步(服务配置):

修改server主机ip为172.25.254.107 (作为dns服务器端)

修改server主机ip为172.25.254.207 (作为dns客户端)

两台主机同时做:

修改yum源为http：//172.25.254.250/rhel7

yum install bind -y

systemctl status named

systemctl start named

systemctl enable named

server主机:

firewall-cmd --permanent --add-service=dns

firewall-cmd --reload

vim /etc/named.conf

修改内容为:

行数内容

11 listen-on port 53 { any; }; ##设定端口开放，any表示所有interface都开

17 allow-query { any; }; ##回答所有人的问题

18 forwarders { 172.25.254.250; }; ##缓存谁的答案

32 dnssec-validation no; ##表示不发布dns表

desktop主机:

vim /etc/resolv.conf

添加内容为:

nameserver 172.25.254.107 ##在第三行添加

然后进行测试,如:

dig www.xxx.com

示例:

[[email protected] ~]# dig www.qq.com

; <<>> DiG 9.9.4-RedHat-9.9.4-14.el7 <<>> www.qq.com

;; global options: +cmd

;; Got answer:

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 26942

;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 4

;; OPT PSEUDOSECTION:

; EDNS: version: 0, flags:; udp: 4096

;; QUESTION SECTION:

;www.qq.com. IN A

;; ANSWER SECTION:

www.qq.com. 300 IN A 113.142.21.81

;; AUTHORITY SECTION:

www.qq.com. 83653 IN NS ns-cnc1.qq.com.

www.qq.com. 83653 IN NS ns-tel1.qq.com.

www.qq.com. 83653 IN NS ns-os1.qq.com.

www.qq.com. 83653 IN NS ns-cmn1.qq.com.

;; ADDITIONAL SECTION:

ns-cmn1.qq.com. 2939 IN A 183.232.120.59

ns-cmn1.qq.com. 2939 IN A 182.254.16.102

ns-cmn1.qq.com. 2939 IN A 182.254.111.100

;; Query time: 53 msec

;; SERVER: 172.25.254.107#53(172.25.254.107)

;; WHEN: Sun Nov 20 01:53:10 EST 2016

;; MSG SIZE rcvd: 190

第二步(正向解析，规范名称-CNAME):

配置(server主机):

修改/etc/named.conf文件的内容:

删除第18行，即，删除 forwarders { 172.25.254.250; };

退出保存

vim /etc/named.rfc1912.zones

修改内容为:

在第25行添加内容为:

25 zone "westos.com" IN {

26 type master;

27 file "westos.com.zone";

28 allow-update { none; };

29 };

退出保存,然后执行:

cd /var/named

cp -p named.localhost westos.com.zone ##一定要加-p，-p的作用是权限

vim /var/named/westos.com.zone

修改文件/var/named/westos.com.zone内容为:

([email protected]@@注意:修改此文件时一定要注意“.”的存在，若不带"."则系统自动往后面添加.westos.com)

1 $TTL 1D

2 @ IN SOA dns.westos.com. root.westos.com. (注意“.”) (

3 0 ; serial

4 1D ; refresh

5 1H ; retry

6 1W ; expire

7 3H ) ; minimum

8 NS dns.westos.com.(注意“.”)

9 dns A 172.25.254.107

10 www A 172.25.254.108

11 AAAA ::1

12 bbs CNAME www.westos.com.

13 westos.com. MX 1 172.25.254.107. ##发送邮件的地址

退出保存后，执行:

systemctl restart named

测试(desktop主机):

[[email protected] ~]# dig www.westos.com

;www.westos.com. IN A

;; ANSWER SECTION:

www.westos.com. 86400 IN A 172.25.254.108

;; AUTHORITY SECTION:

westos.com. 86400 IN NS dns.westos.com.

;; ADDITIONAL SECTION:

dns.westos.com. 86400 IN A 172.25.254.107

;; Query time: 2 msec

;; SERVER: 172.25.254.107#53(172.25.254.107)

;; WHEN: Sun Nov 20 02:26:03 EST 2016

;; MSG SIZE rcvd: 93

[[email protected] ~]# dig bbs.westos.com

;bbs.westos.com. IN A

;; ANSWER SECTION:

bbs.westos.com. 86400 IN CNAME www.westos.com.

www.westos.com. 86400 IN A 172.25.254.108

;; AUTHORITY SECTION:

westos.com. 86400 IN NS dns.westos.com.

;; ADDITIONAL SECTION:

dns.westos.com. 86400 IN A 172.25.254.107

;; Query time: 2 msec

;; SERVER: 172.25.254.107#53(172.25.254.107)

;; WHEN: Sun Nov 20 02:54:42 EST 2016

;; MSG SIZE rcvd: 111

第三步(反向解析):

vim /etc/named.rfc1912.zones

编写/etc/named.rfc1912.zones文件内容:

在第43行添加:

43 zone "254.25.172.in-addr.arpa" IN {

44 type master;

45 file "westos.com.ptr";

46 allow-update { none; };

47 };

退出保存后

cd /var/named

cp -p named.loopback westos.com.ptr

vim westos.com.ptr

内容为:

1 $TTL 1D

2 @ IN SOA dns.westos.com. root.westos.com. (

3 0 ; serial

4 1D ; refresh

5 1H ; retry

6 1W ; expire

7 3H ) ; minimum

8 NS dns.westos.com.

9 A 172.25.254.107

10 AAAA ::1

11 111 PTR www.westos.com.

12 110 PTR www.lover.com.

退出保存后，执行:

systemctl restart named

测试(desktop主机):

使用命令: dig -x 172.25.254.110 （ip值）

[[email protected] ~]# dig -x 172.25.254.110

;110.254.25.172.in-addr.arpa. IN PTR

;; ANSWER SECTION:

110.254.25.172.in-addr.arpa. 86400 IN PTR www.lover.com.

;; AUTHORITY SECTION:

254.25.172.in-addr.arpa. 86400 IN NS dns.westos.com.

;; ADDITIONAL SECTION:

dns.westos.com. 86400 IN A 172.25.254.107

;; Query time: 2 msec

;; SERVER: 172.25.254.107#53(172.25.254.107)

;; WHEN: Sun Nov 20 03:09:51 EST 2016

;; MSG SIZE rcvd: 124

[[email protected] ~]# dig -x 172.25.254.111

;111.254.25.172.in-addr.arpa. IN PTR

;; ANSWER SECTION:

111.254.25.172.in-addr.arpa. 86400 IN PTR www.westos.com.

;; AUTHORITY SECTION:

254.25.172.in-addr.arpa. 86400 IN NS dns.westos.com.

;; ADDITIONAL SECTION:

dns.westos.com. 86400 IN A 172.25.254.107

;; Query time: 2 msec

;; SERVER: 172.25.254.107#53(172.25.254.107)

;; WHEN: Sun Nov 20 03:09:57 EST 2016

;; MSG SIZE rcvd: 118

第四步(双向解析):

配置/etc/named.conf文件，如下:

50 /*zone "." IN {

51 type hint;

52 file "named.ca";

53 };

55 include "/etc/named.rfc1912.zones";

56 include "/etc/named.root.key";

57 */

58 view localnet {

59 match-clients { 172.25.254.107; };

60 zone "." IN {

61 type hint;

62 file "named.ca";

63 };

64 include "/etc/named.rfc1912.zones";

65 };

68 view internet {

69 match-clients { any; };

70 zone "." IN {

71 type hint;

72 file "named.ca";

73 };

74 include "/etc/named.rfc1912.zones.inter";

75 };

退出保存

cp -p /etc/named.rfc1912.zones /etc/named.rfc1912.zones.inter

vim /etc/named.rfc1912.zones.inter

内容为:

25 zone "westos.com" IN {

26 type master;

27 file "westos.com.inter";

28 allow-update { none; };

29 };

43 zone "254.25.172.in-addr.arpa" IN {

44 type master;

45 file "westos.com.ptr.inter";

46 allow-update { none; };

退出保存

cp -p /var/named/westos.com.zone /var/named/westos.com.inter

vim /etc/named/westos.com.inter

修改内容为:

8 NS dns.westos.com.

9 dns A 172.25.0.107

10 www A 172.25.0.108

11 AAAA ::1

12 bbs CNAME www.westos.com.

13 westos.com. MX 1 172.25.0.207.

退出保存

cp -p /var/named/westos.com.ptr /var/named/westos.com.ptr.inter

vim /var/named/westos.com.ptr.inter

修改内容为:

8 NS dns.westos.com.

9 A 172.25.254.107

10 AAAA ::1

11 111 PTR www.force.com.

12 110 PTR www.250.com.

退出保存

然后执行:

systemctl restart named

按照上述顺序，在此处重启服务正常，若想在配置完/etc/named.conf文件后，立即restart服务，则需要把上述顺序颠倒

测试一(server主机):

@@@注意:若出现不匹配现象，则需要修改/etc/resolv.conf 文件，文件内容修改为:

nameserver 172.25.254.107 ##在第三行添加

[[email protected] named]# dig -x 172.25.254.110

;110.254.25.172.in-addr.arpa. IN PTR

;; ANSWER SECTION:

110.254.25.172.in-addr.arpa. 86400 IN PTR www.lover.com.

;; AUTHORITY SECTION:

254.25.172.in-addr.arpa. 86400 IN NS dns.westos.com.

;; ADDITIONAL SECTION:

dns.westos.com. 86400 IN A 172.25.254.107

;; Query time: 2 msec

;; SERVER: 172.25.254.107#53(172.25.254.107)

;; WHEN: Sun Nov 20 04:04:21 EST 2016

;; MSG SIZE rcvd: 124

[[email protected] ~]# dig www.westos.com

;www.westos.com. IN A

;; ANSWER SECTION:

www.westos.com. 86400 IN A 172.25.254.108

;; AUTHORITY SECTION:

westos.com. 86400 IN NS dns.westos.com.

;; ADDITIONAL SECTION:

dns.westos.com. 86400 IN A 172.25.254.107

;; Query time: 1 msec

;; SERVER: 172.25.254.107#53(172.25.254.107)

;; WHEN: Sun Nov 20 04:00:23 EST 2016

;; MSG SIZE rcvd: 93

测试二(desktop主机):

[[email protected] ~]# dig www.westos.com

;www.westos.com. IN A

;; ANSWER SECTION:

www.westos.com. 86400 IN A 172.25.0.108

;; AUTHORITY SECTION:

westos.com. 86400 IN NS dns.westos.com.

;; ADDITIONAL SECTION:

dns.westos.com. 86400 IN A 172.25.0.107

;; Query time: 2 msec

;; SERVER: 172.25.254.107#53(172.25.254.107)

;; WHEN: Sun Nov 20 04:00:02 EST 2016

;; MSG SIZE rcvd: 93

[[email protected] ~]# dig -x 172.25.254.110

;110.254.25.172.in-addr.arpa. IN PTR

;; ANSWER SECTION:

110.254.25.172.in-addr.arpa. 86400 IN PTR www.250.com.

;; AUTHORITY SECTION:

254.25.172.in-addr.arpa. 86400 IN NS dns.westos.com.

;; ADDITIONAL SECTION:

dns.westos.com. 86400 IN A 172.25.0.107

;; Query time: 1 msec

;; SERVER: 172.25.254.107#53(172.25.254.107)

;; WHEN: Sun Nov 20 04:04:38 EST 2016

;; MSG SIZE rcvd: 122

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