ubuntu server guide 学习笔记

1. 软件包

1.1. dpkg

dpkg -l
dpkg -l | grep apache2
dpkg -L ufw
dpkg -S /etc/host.conf
dpkg -i zip_3.0-4_i386.deb
dpkg -r zip

1.2. Apt-Get

1.2.1. apt的相关文件

/etc/apt/sources.list	设置软件包的获取来源
/etc/apt/apt.conf	apt配置文件
/etc/apt/apt.conf.d/	apt的零碎配置文件
/etc/apt/preferences	版本参数
/var/cache/apt/archives/	存放已经下载的软件包
/var/cache/apt/archives/partial	存放正在下载的软件包
/var/lib/apt/lists/	存放已经下载的软件包详细信息
/var/lib/apt/lists/partial/	存放正在下载的软件包详细信息

 

1.2.2. apt-get命令的子命令

update	更新软件包列表
upgrade	升级系统中的所有软件包
install	安装软件包
remove	卸载软件包
autoremove	仅删除不需要再次下载的软件包
purge	彻底删除软件包（包括配置文件）
source	下载源代码
build-dep	自动下载安装编译某个软件所需要的软件包
dist-upgrade	升级整个发行版
dselect-upgrade	安装dselect的选择进行升级
clean	删除本地缓存的所有升级包
autoclean	删除本地缓存中无用的软件包
check	检查是否存在有问题的依赖关系
例:$ sudo apt-get install php5-mysql apache2 $ sudo apt-get update && sudo apt-get upgrade

 

1.2.3. apt-get命令选项

-d,--download-only	仅下载，不安装
-f,--fix-broken	修复依赖问题（用于install和remove子命令）
-m,--ignore-missing,--fix-missing	忽略缺失的软件包。遇到无法下载的软件包，自动忽略
--no-download	禁止下载软件包。与-m配合，可以使apt只使用已经下载的软件包
-q,--quiet	静默模式，输出的信息适合做日志
-s,--simulate,--just-print	模拟测试，不做出实际操作，不改变系统
-y,--yes,--assume-yes	在系统提问时，自动应答yes
-u,--show-upgraded	显示已升级的软件包
-V,--verbose-versions	显示已安装和已升级的软件包的完整版本号
-b,--compile,--build	在源码包下载完成后进行编译
--ignore-hold	忽略被保留的软件包
--no-upgrade	不要升级软件包
--force-yes	强制回答yes
--print-uris	仅答应软件包地址，不安装
--purge	彻底删除，包括配置文件
--reinstall	重新安装软件包

1.2.4. apt-cache命令

功能：搜索某个软件包的名字或显示某个软件包的详细信息
搜索mysql的软件包	$ apt-cache search mysql
查看ssh软件包的详细版本号	$ apt-cache show ssh

 

1.2.5. Red Hat、Fedora和Ubuntu软件包操作对比

任务	Red Hat、Fedora	Ubuntu
基本信息
软件包后缀	*.rpm	*.deb
软件源配置文件	/etc/yum.conf	/etc/apt/sources.list
安装、删除、升级软件包
更新软件包列表	每次运行yum时自动执行	apt-get update
从软件仓库软件安装软件	yum install package	apt-get install package
安装一个已下载的软件包	yum install pkg.rpm rpm -i pkg.rpm	dpkg -i pkg.deb pkg --install pkg.deb
删除软件包	rpm -e package	apt-get remove package
软件包升级检查/测试	yum check-update	apt-get -s upgrade apt-get -s dist-upgrade
升级软件包	yum update rpm -Uvh [args]	apt-get upgrade
升级整个系统	yum upgrade	apt-get dist-upgrade
软件包信息
获取某软件包的信息	yum search package	apt-cache show package
获取所有软件包的信息	yum list available	apt-cache dumpavail
显示所有已安装的软件	yum list installed rpm -qa	dpkg -l dpkg --list
获取某个已安装软件包的信息	yum info package rpm -qi package	dpkg --status package
列出某个已安装软件包所包含的文件列表	rpm -ql package
列出某个已安装软件包所包含的文档	rpm -qd package	无
列出某个已安装软件包所包含的配置文件	rpm -qc package	无
显示某个软件包所依赖的软件包列表	rpm -qR package	apt-cache depends package
显示某个软件包的反向依赖关系	rpm -q -whatrequires [args]	apt-cache rdepends package
软件包文件信息
获取某个软件包文件的信息	rpm -qpi pkg.rpm	dpkg --info pkg.deb
获取某个软件包文件所包含的文件列表	rpm -qpl pkg.rpm	dpkg --contents pkg.deb
获取某个软件包文件所包含的文档	rpm -qpd pkg.rpm	无
获取某个软件包文件所包含的配置文件	rpm -qpc pkg.rpm	无
软件包解压	rpm2cpio pkg.rpm | cpio -vid	dpkg-deb --extract pkg.deb
搜索某个文件是由哪个软件包安装的	rpm -qf /file/name	dpkg -S /file/name dpkg --search /file/name
搜索所有提供某个文件的软件包	yum provides /file/name	apt-file search /file/name
杂项
显示本地软件包缓存的状态	无	apt-cache stats
校验所有已安装的软件包	rpm -Va	debsums
删除本地缓存的所有软件包	yum clean packages	apt-get clean
仅删除本地缓存中过时的软件包	无	apt-get autoclean
删除所有软件包信息	yum clean headers	apt-file purge

1.2.6. apt源

apt-get install nmap

apt-get remove nmap

apt-get update     --更新源

apt-get upgrade    --升级软件包

deb 软件的位置

deb-src  软件的源代码的位置

限定词：

main：完全的自由软件。

restricted：不完全的自由软件。

universe：ubuntu官方不提供支持与补丁，全靠社区支持。

muitiverse：非自由软件，完全不提供支持和补丁。

1、原文件备份

sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak

2、编辑源列表文件

deb https://mirrors.aliyun.com/ubuntu/ trusty main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ trusty main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiverse

deb https://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiverse

deb https://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiverse

## Not recommended
# deb https://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiverse
# deb-src https://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiverse

3、运行sudo apt-get update

1.3. Aptitude

aptitude

aptitude install nmap

aptitude remove nmap

2. Network

ifconfig|grep eth

lshw -class network

apt-get install ethtool

ethtool eth0

2.1. ip设置

临时设置：

ifconfig eth0 10.0.0.100 netmask 255.255.255.0
route add default gw 10.0.0.1 eth0
route -n

ip addr flush eth0  --清除ip设置

dhcp获取ip

auto eth0
iface eth0 inet dhcp

静态ip

auto eth0
iface eth0 inet static
address 10.0.0.100
netmask 255.255.255.0
gateway 10.0.0.1

ifdown eth0 && ifup eth0  --重启网络

2.2. dns设置

vim /etc/resolv.conf

nameserver 8.8.8.8
nameserver 8.8.4.4

网卡配置文件

iface eth0 inet static
    address 192.168.3.3
    netmask 255.255.255.0
    gateway 192.168.3.1
    dns-search example.com
    dns-nameservers 192.168.3.45 192.168.8.10 

2.3. 静态主机名

vim /etc/hosts

127.0.0.1 localhost
127.0.1.1 ubuntu-server
10.0.0.11 server1 server1.example.com vpn
10.0.0.12 server2 server2.example.com mail
10.0.0.13 server3 server3.example.com www
10.0.0.14 server4 server4.example.com file

2.4. 域名解析顺序

vim  /etc/nsswitch.conf

hosts:          files mdns4_minimal [NOTFOUND=return] dns mdns4
• files first tries to resolve static hostnames located in  /etc/hosts .
• mdns4_minimal attempts to resolve the name using Multicast DNS.
• [NOTFOUND=return] means that any response of notfound by the preceding mdns4_minimal process
should be treated as authoritative and that the system should not try to continue hunting for an answer.
• dns represents a legacy unicast DNS query.
• mdns4 represents a Multicast DNS query.

2.5. 桥接

apt-get install bridge-utils

vim  /etc/network/interfaces

auto lo
iface lo inet loopback
auto br0
iface br0 inet static
        address 192.168.0.10
        network 192.168.0.0
        netmask 255.255.255.0
        broadcast 192.168.0.255
        gateway 192.168.0.1
        bridge_ports eth0
        bridge_fd 9
        bridge_hello 2
        bridge_maxage 12
        bridge_stp off

brctl show

2.6. man

2.6.1. man interfaces

pre-up command
              Run command before bringing the interface up.  If this command fails then ifup aborts, refraining from marking the interface as configured, prints  an  error
message, and exits with status 0.  This behavior may change in the future.

post-up command
              Run  command after bringing the interface up.  If this command fails then ifup aborts, refraining from marking the interface as configured  (even  though  it has really been configured), prints an error message, and exits with status 0.This behavior may change in the future.

pre-down command
              Run command before taking the interface down.   If  this  command  fails  then ifdown  aborts,  marks  the  interface as deconfigured (even though it has not really been deconfigured), and exits with status 0.  This behavior may  change in the future.

post-down command
              Run  command  after  taking  the  interface  down.  If this command fails then ifdown aborts, marks the interface as deconfigured, and exits with  status  0.This behavior may change in the future.

2.6.2. man ifup

ifup -a

ifdown -a

ifquery -l

-i FILE, --interfaces=FILE

Read interface definitions from FILE instead of from /etc/network/interfaces.

2.6.3. man resolvconf

# vim /etc/resolv.conf

dns-nameservers 192.168.1.254 8.8.8.8
dns-search foo.org bar.com

# ll /etc/resolv.conf

lrwxrwxrwx 1 root root 29 Jun 14 02:40 /etc/resolv.conf -> ../run/resolvconf/resolv.conf

2.7. dhcp

apt-get install isc-dhcp-server

# vim /etc/dhcp/dhcpd.conf

default-lease-time 600;
max-lease-time 7200;
subnet 192.168.1.0 netmask 255.255.255.0 {
 range 192.168.1.150 192.168.1.200;
 option routers 192.168.1.254;
 option domain-name-servers 192.168.1.1, 192.168.1.2;
 option domain-name "mydomain.example";
}

2.8. ntp

ntpdate -s ntp.ubuntu.com

apt-get install ntp

#vim  /etc/ntp.conf

server 0.ubuntu.pool.ntp.org
server 1.ubuntu.pool.ntp.org
server 2.ubuntu.pool.ntp.org
server 3.ubuntu.pool.ntp.org

# ntpq -p

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
+stratum2-2.NTP. 129.70.130.70    2 u    5   64  377   68.461  -44.274 110.334
+ntp2.m-online.n 212.18.1.106     2 u    5   64  377   54.629  -27.318  78.882
*145.253.66.170  .DCFa.           1 u   10   64  377   83.607  -30.159  68.343
+stratum2-3.NTP. 129.70.130.70    2 u    5   64  357   68.795  -68.168 104.612
+europium.canoni 193.79.237.14    2 u   63   64  337   81.534  -67.968  92.792

3. multipath

service multipath-tools stop

multipath -F

service multipath-tools start

service multipath-tools reload

multipathd help    --显示相关命令

multipathd -k  进入命令输入界面

echo 'show config' | multipathd -k

Every time either  /etc/lvm.conf  or  /etc/multipath.conf  is updated, the initrd should be rebuilt toreflect these changes.

update-initramfs -u -k all

Before setting up DM-Multipath on your system, ensure that your system has been updated and includes the multipath-tools package. If boot from SAN is desired, then the multipath-tools-boot package is also required.

3.1. Resizing an Online Multipath Device

If you need to resize an online multipath device, use the following procedure

1. Resize your physical device. This is storage platform specific.

2. Use the following command to find the paths to the LUN:

# multipath -l

3. Resize your paths. For SCSI devices, writing 1 to the  rescan  file for the device causes the SCSI driver to

rescan, as in the following command:

# echo 1 > /sys/block/device_name/device/rescan

4. Resize your multipath device by running the multipathd resize command:

# multipathd -k 'resize map mpatha'

5. Resize the file system (assuming no LVM or DOS partitions are used):

# resize2fs /dev/mapper/mpatha

3.2. troubleshotting

# multipathd -k

> > show config

> > CTRL-D

The following command sequence ensures that multipath has picked up any changes to the multipath.conf,

# multipathd -k

> > reconfigure

> > CTRL-D

Use the following command sequence to ensure that the path checker is working properly.

# multipathd -k

> > show paths

> > CTRL-D

Commands can also be streamed into multipathd using stdin like so:

# echo 'show config' | multipathd -k

4. 远程管理

4.1. ssh

apt-get install openssh-client

apt-get install openssh-server

备份配置文件

cp /etc/ssh/sshd_config /etc/ssh/sshd_config.original

chmod a-w /etc/ssh/sshd_config.original

service ssh restart

ssh-keygen -t rsa

ssh-copy-id username@remotehost

chmod 600 .ssh/authorized_keys

4.2. puppet

Puppet server's  /etc/hosts  file add:

127.0.0.1 localhost.localdomain localhost puppet

192.168.1.17 puppetclient.example.com puppetclient

On each Puppet client, add an entry for the server:

192.168.1.16 puppetmaster.example.com puppetmaster puppet

apt-get install puppetmaster   --服务端

apt-get install puppet          --客户端

服务端

mkdir -p /etc/puppet/modules/apache2/manifests

# vim  /etc/puppet/modules/apache2/manifests/init.pp

containing the following:
class apache2 {
  package { 'apache2':
    ensure => installed,
  }
  service { 'apache2':
    ensure  => true,
    enable  => true,
    require => Package['apache2'],
  }
}

# vim  /etc/puppet/manifests/site.pp

node 'puppetclient.example.com' {
   include apache2
}

service puppetmaster restart

客户端

First, configure the Puppet agent daemon to start. Edit  /etc/default/puppet ,changing START to yes:

START=yes

Then start the service:

sudo service puppet start

View the client cert fingerprint

sudo puppet agent --fingerprint

Back on the Puppet server, view pending certificate signing requests:

sudo puppet cert list

On the Puppet server, verify the fingerprint of the client and sign puppetclient's cert:

sudo puppet cert sign puppetclient.example.com

On the Puppet client, run the puppet agent manually in the foreground. This step isn't strictly speaking necessary, but it is the best way to test and debug the puppet service.

sudo puppet agent --test

Check  /var/log/syslog  on both hosts for any errors with the configuration. If all goes well the apache2 package and it's dependencies will be installed on the Puppet client.

5. DNS

sudo apt-get install bind9

sudo apt-get install dnsutils           --测试和排障

/etc/bind/named.conf

/etc/bind/named.conf.options

/etc/bind/db.root

6. 安全

6.1. 用户管理

开启root

sudo passwd

禁用root密码

sudo passwd -l root

禁用root账号

usermod --expiredate 1

man sudo

/etc/sudoers

6.1.1. 用户操作

创建和删除用户

sudo adduser username

sudo deluser username

锁住和解锁用户

sudo passwd -l username

sudo passwd -u username

增加和删除组

sudo addgroup groupname

sudo delgroup groupname

添加用户到组

sudo adduser username groupname

用户属性

ls -ld /home/username

sudo chmod 0750 /home/username

vim /etc/adduser.conf

DIR_MODE=0750

6.1.2. 密码策略

密码长度

/etc/pam.d/common-password

password        [success=1 default=ignore]      pam_unix.so obscure sha512 minlen=8

查看用户密码状态

sudo chage -l username

设置密码策略

sudo chage username

sudo chage -E 01/31/2015 -m 5 -M 90 -I 30 -W 14 username

6.1.3. ssh连接

who | grep username  (to get the pts/# terminal)

sudo pkill -f pts/#

6.2. console安全

6.2.1. Disable Ctrl+Alt+Delete

/etc/init/control-alt-delete.conf

#exec shutdown -r now "Control-Alt-Delete pressed"

6.3. Firewall

sudo ufw enable

sudo ufw allow 22

sudo ufw insert 1 allow 80

sudo ufw deny 22

sudo ufw delete deny 22

sudo ufw allow proto tcp from 192.168.0.2 to any port 22

sudo ufw --dry-run allow http    --测试

sudo ufw disable

sudo ufw status

6.3.1. ufw Application Integration

配置文件 /etc/ufw/applications.d

sudo ufw app list

sudo ufw allow Samba

ufw allow from 192.168.0.0/24 to any app Samba

ufw app info Samba

6.3.2. IP Masquerading

1) ufw Masquerading

First, packet forwarding needs to be enabled in ufw. Two configuration files will need to be adjusted, in  /etc/default/ufw  change the DEFAULT_FORWARD_POLICY to “ACCEPT”:

DEFAULT_FORWARD_POLICY="ACCEPT"

Then edit  /etc/ufw/sysctl.conf  and uncomment:

net/ipv4/ip_forward=1

Now add rules to the  /etc/ufw/before.rules  file. The default rules only configure the filter table, and to enable masquerading the nat table will need to be configured. Add the following to the top of the file just after the header comments:

# nat Table rules
*nat
:POSTROUTING ACCEPT [0:0]

# Forward traffic from eth1 through eth0.
-A POSTROUTING -s 192.168.0.0/24 -o eth0 -j MASQUERADE

# don't delete the 'COMMIT' line or these nat table rules won't be processed
COMMIT

重启ufw

sudo ufw disable && sudo ufw enable

2) iptables Masquerading

Similar to ufw, the first step is to enable IPv4 packet forwarding by editing  /etc/sysctl.conf  and

uncomment the following line:

net.ipv4.ip_forward=1

sudo sysctl -p

sudo iptables -t nat -A POSTROUTING -s 192.168.0.0/16 -o ppp0 -j MASQUERADE

sudo iptables -A FORWARD -s 192.168.0.0/16 -o ppp0 -j ACCEPT

sudo iptables -A FORWARD -d 192.168.0.0/16 -m state \

--state ESTABLISHED,RELATED -i ppp0 -j ACCEPT

6.3.3. Logs

sudo ufw logging on

sudo ufw logging off

If using iptables instead of ufw, enter:

sudo iptables -A INPUT -m state --state NEW -p tcp --dport 80 \
-j LOG --log-prefix "NEW_HTTP_CONN: "

A request on port 80 from the local machine, then, would generate a log in dmesg that looks like this (single line split into 3 to fit this document):

[4304885.870000] NEW_HTTP_CONN: IN=lo OUT= MAC=00:00:00:00:00:00:00:00:00:00:00:00:08:00
SRC=127.0.0.1 DST=127.0.0.1 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=58288 DF PROTO=TCP
SPT=53981 DPT=80 WINDOW=32767 RES=0x00 SYN URGP=0

The above log will also appear in  /var/log/messages ,  /var/log/syslog , and  /var/log/kern.log

7. 文件服务

7.1. vsftpd

sudo apt-get install vsftpd

edit  /etc/vsftpd.conf  by changing:

anonymous_enable=Yes

修改ftp家目录

sudo mkdir /srv/files/ftp

sudo usermod -d /srv/files/ftp ftp

重启服务

sudo restart vsftpd

7.2. nfs

sudo apt-get install nfs-kernel-server

vim   /etc/exports

/ubuntu  *(ro,sync,no_root_squash)

/home    *(rw,sync,no_root_squash)

sudo service nfs-kernel-server start

客户端

sudo apt-get install nfs-common

sudo mount example.hostname.com:/ubuntu /local/ubuntu

vim /etc/fstab

example.hostname.com:/ubuntu /local/ubuntu nfs rsize=8192,wsize=8192,timeo=14,intr

7.3. iSCSI Initiator

sudo apt-get install open-iscsi

edit  /etc/iscsi/iscsid.conf

node.startup = automatic

sudo iscsiadm -m discovery -t st -p 192.168.0.10

192.168.0.10:3260,1 iqn.1992-05.com.emc:sl7b92030000520000-2

sudo iscsiadm -m node --login

sudo fdisk /dev/sdb

n

p

enter

w

sudo mkfs.ext4 /dev/sdb1

sudo mount /dev/sdb1 /srv

vim /etc/fstab

/dev/sdb1       /srv        ext4    defaults,auto,_netdev 0 0

8. 备份

#!/bin/bash
####################################
#
# Backup to NFS mount script.
#
####################################
# What to backup.
backup_files="/home /var/spool/mail /etc /root /boot /opt"

# Where to backup to.
dest="/mnt/backup"

# Create archive filename.
day=$(date +%A)
hostname=$(hostname -s)
archive_file="$hostname-$day.tgz"

# Print start status message.
echo "Backing up $backup_files to $dest/$archive_file"
date
echo

# Backup the files using tar.
tar czf $dest/$archive_file $backup_files
# Print end status message.
echo
echo "Backup finished"
date

# Long listing of files in $dest to check file sizes.
ls -lh $dest

chmod u+x backup.sh

sudo ./backup.sh

sudo crontab -e

0 0 * * * bash /usr/local/bin/backup.sh

还原

tar -tzvf /mnt/backup/host-Monday.tgz

tar -xzvf /mnt/backup/host-Monday.tgz -C /tmp etc/hosts

另外一个shell脚本

#!/bin/bash
####################################
#
# Backup to NFS mount script with
# grandfather-father-son rotation.
#
####################################
# What to backup.
backup_files="/home /var/spool/mail /etc /root /boot /opt"

# Where to backup to.
dest="/mnt/backup"

# Setup variables for the archive filename.
day=$(date +%A)
hostname=$(hostname -s)

# Find which week of the month 1-4 it is.
day_num=$(date +%d)
if (( $day_num <= 7 )); then
        week_file="$hostname-week1.tgz"
elif (( $day_num > 7 && $day_num <= 14 )); then
        week_file="$hostname-week2.tgz"
elif (( $day_num > 14 && $day_num <= 21 )); then
        week_file="$hostname-week3.tgz"
elif (( $day_num > 21 && $day_num < 32 )); then
        week_file="$hostname-week4.tgz"
fi

# Find if the Month is odd or even.
month_num=$(date +%m)
month=$(expr $month_num % 2)
if [ $month -eq 0 ]; then
        month_file="$hostname-month2.tgz"
else
        month_file="$hostname-month1.tgz"
fi

# Create archive filename.
if [ $day_num == 1 ]; then
 archive_file=$month_file
elif [ $day != "Saturday" ]; then
        archive_file="$hostname-$day.tgz"
else
 archive_file=$week_file
fi

# Print start status message.
echo "Backing up $backup_files to $dest/$archive_file"
date
echo

# Backup the files using tar.
tar czf $dest/$archive_file $backup_files

# Print end status message.
echo
echo "Backup finished"
date

# Long listing of files in $dest to check file sizes.
ls -lh $dest/

9. kvm

kvm-ok  --检查是否支持kvm

sudo apt-get install qemu-kvm libvirt-bin

sudo adduser $USER libvirtd

sudo apt-get install virtinst

sudo virt-install -n web_devel -r 256 \
--disk path=/var/lib/libvirt/images/web_devel.img,bus=virtio,size=4 -c \
ubuntu-14.04-server-i386.iso --network network=default,model=virtio \
--graphics vnc,listen=0.0.0.0 --noautoconsole -v

sudo virt-clone -o web_devel -n database_devel -f /path/to/database_devel.img \

--connect=qemu:///system

virsh -c qemu:///system list
virsh -c qemu:///system start web_devel
virsh -c qemu:///system autostart web_devel
virsh -c qemu:///system reboot web_devel
virsh -c qemu:///system save web_devel web_devel-022708.state
virsh -c qemu:///system restore web_devel-022708.state
virsh -c qemu:///system shutdown web_devel
virsh -c qemu:///system attach-disk web_devel /dev/cdrom /media/cdrom

sudo apt-get install virt-manager

virt-manager -c qemu:///system

virt-manager -c qemu+ssh://virtnode1.mydomain.com/system  --用其他主机连接

sudo apt-get install virt-viewer

virt-viewer -c qemu:///system web_devel

virt-viewer -c qemu+ssh://virtnode1.mydomain.com/system web_devel

10. 开机启动项

sudo update-rc.d -f  boa remove   --删除启动项

sudo update-rc.d  boa default      --添加启动项

sudo apt-get install bum  #图形界面

sudo apt-get install sysv-rc-conf #字符界面

sudo bum

sudo sysv-rc-conf #进入交互界面

sudo sysv-rc-conf --list #直接打印列表

11. 图形桌面

apt install xinit

apt install gdm

apt install ubuntu-desktop    --gnome桌面

apt install kubuntu-desktop   --kde桌面

ubuntu系统运行级别，runlevel

0       系统停机状态

1       单用户或系统维护状态

2~5     多用户状态

6       重新启动

修改系统运行级别

vim /etc/init/rc-sysinit.conf

entry env DEFAULT_RUNLEVEL=2