After installation of the system configuration and optimization CentOS7

1. Configuring source and domestic source epel

   /etc/yum.repos.d/ cd
   mkdir repo_bak
   mv * .repo repo_bak /
   # source file basis
   wget -P /etc/yum.repos.d/ http://mirrors.aliyun.com/repo/Centos-7. repo
   #epel source file
   wget -O /etc/yum.repos.d/epel-7.repo http://mirrors.aliyun.com/repo/epel-7.repo
   # regenerate the cache yum
   yum Clean All
   yum makecache
   # upgrade the system
   yum update -y

2. Mounting base dependencies

   yum install -y htop lrzsz nmap screen man expect \
   gcc gcc-c++ autoconf automake bzip2-devel \
   openssl-devel multitail kernel-devel \
   pam-devel zlib-devel perl-devel tcp_wrappers-devel

3. Close selinux

   -i Sed 'S / the SELINUX = ^. * / the SELINUX = Disabled / G' / etc / selinux / config
   the setenforce 0
   # selinux provided See
   getenforce

4. Turn off the default mail service

   # (Default port 25)
   systemctl disable postfix
   systemctl STOP postfix
   # view the system default listening ports
   netstat -nlput | grep -v "Proto" | grep "LISTEN"

5. Set system environment variables

   # Add execute permissions
   chmod A + the X-/etc/rc.d/rc.local
   # set the environment variable
   cat >> / etc / profile << EOF

   $(date +%F)

   VI = Alias 'Vim'
   Alias = grep '= Auto --color grep'
   # 300 seconds is provided to a user operation field without disconnecting the terminal
   Export the TMOUT = 300
   # The value to prevent users from changing readonly
   readonly the TMOUT
   the EOF
   Source / etc / Profile
   #vimrc provided
   CAT >> / etc / << the vimrc the EOF
   sET = TabStop. 4
   sET = softtabstop. 4
   sET = shiftwidth. 4
   sET expandtab
   the EOF

6. Open File Set Descriptor

   cat >/etc/security/limits.conf <<EOF
   ##### $(date) #####
   * soft noproc 65535
   * hard noproc 65535
   * soft nofile 409600
   * hard nofile 409600
   EOF

7. Optimize system kernel parameters

   Optimize the kernel parameter ### ###
   IF [-f '/etc/sysctl.conf.bak'!]; The then
   \} CP /etc/sysctl.conf{,.bak
   CAT> << /etc/sysctl.conf EOF

   $(date)

   # Modify the maximum number of connections
   net.nf_conntrack_max = 655360
   net.netfilter.nf_conntrack_tcp_timeout_established = 1200
   # socket is closed by the end of this time it must parameter FIN-WAIT-2 state, default is 60 seconds.
   net.ipv4.tcp_fin_timeout = 2
   the number of retries before #socket waste, heavily loaded web server is recommended to decrease
   net.ipv4.tcp_orphan_retries. 1 =
   # indicate on reuse. TIME-WAIT sockets allow re-used for new TCP connection.
   =. 1 net.ipv4.tcp_tw_reuse
   # represents enable the rapid recovery of TCP connection of TIME-WAIT sockets.
   = 1 net.ipv4.tcp_tw_recycle
   # indicate on SYN Cookies. When the SYN queue overflow occurs, enable cookies to deal with, can prevent a small amount of SYN ***.
   =. 1 net.ipv4.tcp_syncookies
   # represents the time when only use keepalive, TCP transmission frequency of keepalive messages. The default is 2 hours to 10 minutes.
   = 600 net.ipv4.tcp_keepalive_time
   # indicates a port range outgoing connections. By default small: 32768-61000, instead 1024-65000.
   net.ipv4.ip_local_port_range = 1024 65000
   # SYN increase the queue length, the default is 1024. The number of network connections may accommodate more wait for a connection.
   net.ipv4.tcp_max_syn_backlog = 262144
   number #imewait, the default is 180,000.
   6000 = net.ipv4.tcp_max_tw_buckets
   # route cache refresh rate, when a route fails how long jump to another route, the default is 300.
   = 100 net.ipv4.route.gc_timeout
   # kernel abandoning transmission of SYN + ACK before the connection time
   net.ipv4.tcp_syn_retries. 1 =
   # Number of transmitted core abandon the SYN packet to establish a connection before.
   =. 1 net.ipv4.tcp_synack_retries
   # mediation systems simultaneously initiated number of TCP connections, the default is 128. highly concurrent request, the default value may cause connection timeout or retransmission.
   = 262144 net.core.somaxconn
   # This parameter determines, when the rate of the fast rate of the received data packet network device packages than those processing cores, the maximum allowed number of packets to the queue.
   = 262144 net.core.netdev_max_backlog
   # to set the system up to the number of TCP sockets are not linked to any user file handle. To prevent simple DoS ***.
   = 262144 net.ipv4.tcp_max_orphans
   the EOF
   Fi
   # refresh system kernel parameters:
   / sbin / sysctl -p