centos7官方的ISO镜像太大且安装时间太久，线上应用往往只需要使用部分的包，定制化可以有效精简镜像和减少安装时间，通过定制化的KS文件更是可以进行操作系统的初始化配置。

一、获取官方ISO镜像

CentOS7的官方ISO镜像自行下载，下载后挂载到自己的虚拟并将ISO文件拷贝出来

mount /dev/cdrom /media
mkdir centos ; cd centos ; cp -ra /media/* .

二、安装镜像制作工具

yum -y install createrepo mkisofs

三、KS文件制作

3.1 KS文件的语法自行学习，可以从一台已经安装好的服务器的/root/anaconda-ks.cfg拷下来修改并放到镜像文件里的isolinux目录。

cp /root/anaconda-ks.cfg /root/centos/isolinux/ks.cfg

install
cdrom	# Use CDROM installation media
text	# Use text install
# Keyboard layouts
keyboard --vckeymap=us --xlayouts='us'
# System language
lang en_US.UTF-8
# System services
services --disabled="chronyd"
# System timezone
timezone Asia/Shanghai --isUtc

# SELinux configuration
selinux --disabled
# Firewall configuration
firewall --disabled
# Network information
network  --bootproto=dhcp --device=eth0 --onboot=yes --ipv6=no --no-activate
network  --hostname=localhost.localdomain

# System authorization information
auth --enableshadow --passalgo=sha512
# user password
rootpw --iscrypted $6$z4ecbtnCwYNRgJVy$F.vv.twuNIfJQZF6tcEbyJ7Dcyw2ZYt4X0zwFG6nf0FRGVIEYJtDTpr4qmblRjZSd7UTt9XUUlp2S7LQDM9Fs/
user --name=Apps --password=$6$gAIUkrddD/qYdtb1$utKAaA6T/8qWcI/79SrP3xcVvMuA6/8SjHOrJzuSv5tKIwrzVBggkuUL7hLbPUPJNHfbs90jJIUH2NnKDCULm1 --iscrypted --gecos="apps"



# Run the Setup Agent on first boot
firstboot --disabled
# Clear the Master Boot Record
zerombr   
ignoredisk --only-use=sda
# System bootloader configuration
bootloader --append=" crashkernel=auto" --location=mbr --boot-drive=sda
# Partition clearing information
clearpart --all --initlabel --drives=sda
# Disk partitioning information
part / --asprimary --fstype="ext4" --size=51200
part /boot --asprimary --fstype="ext4" --size=1024
part swap --fstype="swap"--size=8192
part /home --fstype="ext4" --grow --size=1

%packages
@base
@compat-libraries
@core
kexec-tools
vim
lrzsz
%end

%addon com_redhat_kdump --enable --reserve-mb='auto'

%end

%post
mv /bin/vi /bin/vi.bak && ln -s /bin/vim /bin/vi
systemctl disable NetworkManager
systemctl stop NetworkManager

# SSH
sed -i "s@#Port 22@Port 8222@g" /etc/ssh/sshd_config
sed -i "s@#PermitRootLogin yes@PermitRootLogin no@g" /etc/ssh/sshd_config
sed -i "s@GSSAPIAuthentication yes@GSSAPIAuthentication no@g" /etc/ssh/sshd_config

# 系统优化
echo -e "* soft nofile 262144n* hard nofile 262144n* soft nproc 65535n* hard nproc 65535" >>/etc/security/limits.conf
sed -i "s@*@#*@g" /etc/security/limits.d/20-nproc.conf
sed -i "s@root@#root@g" /etc/security/limits.d/20-nproc.conf

cat > /etc/sysctl.conf << EOF
# TCP 
net.ipv4.tcp_fin_timeout = 30
net.ipv4.tcp_keepalive_time = 3600
net.ipv4.tcp_keepalive_intvl = 15
net.ipv4.tcp_keepalive_probes = 3
net.ipv4.tcp_max_tw_buckets  = 20480
net.ipv4.tcp_max_syn_backlog = 65535
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_synack_retries = 2
net.ipv4.tcp_syn_retries = 2
net.ipv4.tcp_timestamps = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_orphan_retries = 3
net.ipv4.tcp_max_orphans = 65536
net.ipv4.ip_forward = 1
net.ipv4.ip_local_port_range = 1024  65535
net.core.netdev_max_backlog = 30000
net.core.somaxconn = 65535
fs.file-max = 262144

# TCP memory
net.ipv4.tcp_rmem = 4096 4096 16777216
net.ipv4.tcp_wmem = 4096 4096 16777216
net.ipv4.tcp_mem = 786432 2097152 3145728
net.core.rmem_default = 262144
net.core.wmem_default = 262144
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216

# ipv6
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
EOF

%end

# Reboot after installation
reboot

3.2 修改引导加载程序

cd /root/centos/isolinux;	vi isolinux.cfg

label linux
  menu label ^Install CentOS 7
  menu default
  kernel vmlinuz
  #在quit后面添加inst.ks=cdrom:/isolinux/ks.cfg net.ifnames=0 bIOSdevname=0
  #LABEL=CentOS7与下面生成镜像指定的保持一致
  append initrd=initrd.img inst.stage2=hd:LABEL=CentOS7 quiet inst.ks=cdrom:/isolinux/ks.cfg net.ifnames=0 biosdevname=0

四、精简安装包

4.1 进入Packages目录 下，根据自己的实际情况精简不需要用的安装包。

cd /root/centos/Packages

4.2 制作comps文件，将repodata目录下除“*-comps.xml”的所有文件删除，并将“*-comps.xml”文件改为comps.xml

cd /root/centos/repodata; rm -rf *.bz2 *.gz repomd.xml TRANS.TBL 
mv cca56f*-comps.xml comps.xml

4.3 重新生成repodata目录和文件

cd /root/centos; createrepo -g repodata/comps.xml .

四、生成ISO镜像

cd /root/centos
genisoimage -joliet-long -V CentOS7 -o /root/CentOS7-v1-x86_64.iso -b isolinux/isolinux.bin -c isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -R -J -v -cache-inodes -T -eltorito-alt-boot -e images/efiboot.img -no-emul-boot /root/centos

至此、精简镜像的工作就完成了，我这里精简后的镜像还有1.1G。