查看进程

控制进程

进程之间关系

进程通信方式

信号

Kill

守护进程

一般进程都是通过命令终端输入启动然后前台或者后台执行，而守护进程是机器刚刚开机就自动启动的进程，同时守护进程在执行过程中会打印相应日志到指定目录中，除此之外守护进程存在与根目录下，不会导致磁盘或光盘等介质无法卸载。

nohup … &

使用nobup命令打开一个进程，与守护进程类似，在关闭终端后，仍然可以执行。也即 nohub 命令使进程忽略 hangup(挂起)信号—比如说关闭执行命令终端。

在一个终端下执行 tail 进程，另一个终端下查询进程
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关闭第一个终端后，再次查看进程发现没有虚拟终端在运行
image.png
使用 nohub 和 &结合将 tail 命令进程在后台执行，并且不会受到关闭终端的影响，而且忽略输入将输出内容打印到当前目录的 nohup.out文件中
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在另一个终端中发现该进程的父进程即终端进程结束后，变为 1,即孤儿进程被祖先进程收养
image.png

守护进程daemon

不需要终端的进程，与 nohup命令相比：父进程不是终端进程，而是祖先进程；输出不是终端而是指定日志目录；使用的目录切换为根目录，只有在重启时进程才可结束

进入系统自动创建的相应进程号目录，文件和目录显示进程信息
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查看进程执行目录，为 /root目录，不能随便卸载
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0表示标准输入，表示关闭 1、2表示标准输出
image.png

查看demon进程 sshd
image.png
sshd守护进程父进程为1，进入到该进程目录下，发现执行路径为根目录 /，标注输入为 关闭， 标准输出为 socket套接字，输出信息到 /var/log/sshd目录下。

nohup 和 守护进程运行的进程都可以脱离终端，避免关闭终端后，出现异常

screen

进行终端操作时，进入screen环境，即使终端关闭或者网络中断，再次打开后仍然可以继续执行

screen 进入screen环境
ctrl+a d 退出（detached）screen环境
screen -ls 查看screen会话
screen -r sessionid 恢复会话
exit 结束screen进程

安装并进入screen环境
image.pngimage.png

执行命令进程
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ctrl + a d退出screen环境
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查看保留session

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恢复指定session环境
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image.png

服务管理工具

服务，也就是守护进程，可以通过以下两种工具集中管理

service

Centos 6之前使用

  1. [root@centos7 ~]# cd /etc/init.d/
  2. [root@centos7 init.d]# cat network

以下是network的启停脚本

  1. #! /bin/bash
  2. #
  3. # network       Bring up/down networking
  4. #
  5. # chkconfig: 2345 10 90
  6. # description: Activates/Deactivates all network interfaces configured to \
  7. #              start at boot time.
  8. #
  9. ### BEGIN INIT INFO
  10. # Provides: $network
  11. # Should-Start: iptables ip6tables NetworkManager-wait-online NetworkManager $network-pre
  12. # Short-Description: Bring up/down networking
  13. # Description: Bring up/down networking
  14. ### END INIT INFO
  16. # Source function library.
  17. . /etc/init.d/functions
  19. if [ ! -f /etc/sysconfig/network ]; then
  20.     exit 6
  21. fi
  23. . /etc/sysconfig/network
  25. if [ -f /etc/sysconfig/pcmcia ]; then
  26.         . /etc/sysconfig/pcmcia
  27. fi
  30. # Check that networking is up.
  31. [ "${NETWORKING}" = "no" ] && exit 6
  33. # if the ip configuration utility isn't around we can't function.
  34. [ -x /sbin/ip ] || exit 1
  37. CWD=$(pwd)
  38. cd /etc/sysconfig/network-scripts
  40. . ./network-functions
  42. # find all the interfaces besides loopback.
  43. # ignore aliases, alternative configurations, and editor backup files
  44. interfaces=$(ls ifcfg-* | \
  45.             LC_ALL=C sed -e "$__sed_discard_ignored_files" \
  46.                        -e '/\(ifcfg-lo$\|:\|ifcfg-.*-range\)/d' \
  47.                        -e '{ s/^ifcfg-//g;s/[0-9]/ &/}' | \
  48.             LC_ALL=C sort -k 1,1 -k 2n | \
  49.             LC_ALL=C sed 's/ //')
  50. rc=0
  52. # See how we were called.
  53. case "$1" in
  54.   start)
  55.         [ "$EUID" != "0" ] && exit 4
  56.         rc=0
  57.         # IPv6 hook (pre IPv4 start)
  58.         if [ -x /etc/sysconfig/network-scripts/init.ipv6-global ]; then
  59.                 /etc/sysconfig/network-scripts/init.ipv6-global start pre
  60.         fi
  62.         apply_sysctl
  64.         #tell NM to reload its configuration
  65.         if [ "$(LANG=C nmcli -t --fields running general status 2>/dev/null)" = "running" ]; then
  66.                 nmcli connection reload
  67.         fi
  69.         # bring up loopback interface
  70.         action $"Bringing up loopback interface: " ./ifup ifcfg-lo
  72.         case "$VLAN" in
  73.           yes)
  74.             if [ ! -d /proc/net/vlan ] && ! modprobe 8021q >/dev/null 2>&1 ; then
  75.                 net_log $"No 802.1Q VLAN support available in kernel."
  76.             fi
  77.             ;;
  78.         esac
  80.         vlaninterfaces=""
  81.         vpninterfaces=""
  82.         xdslinterfaces=""
  83.         bridgeinterfaces=""
  85.         # bring up all other interfaces configured to come up at boot time
  86.         for i in $interfaces; do
  87.                 unset DEVICE TYPE SLAVE
  88.                 eval $(LANG=C grep -F "DEVICE=" ifcfg-$i)
  89.                 eval $(LANG=C grep -F "TYPE=" ifcfg-$i)
  90.                 eval $(LANG=C grep -F "SLAVE=" ifcfg-$i)
  91.                 eval $(LANG=C grep -F "NM_CONTROLLED=" ifcfg-$i)
  93.                 if [ -z "$DEVICE" ] ; then DEVICE="$i"; fi
  95.                 if [ "$SLAVE" = "yes" ] && ( ! is_nm_running || is_false $NM_CONTROLLED ) ; then
  96.                         continue
  97.                 fi
  99.                 if [ "${DEVICE##cipcb}" != "$DEVICE" ] ; then
  100.                         vpninterfaces="$vpninterfaces $i"
  101.                         continue
  102.                 fi
  103.                 if [ "$TYPE" = "xDSL" ]; then
  104.                         xdslinterfaces="$xdslinterfaces $i"
  105.                         continue
  106.                 fi
  108.                 if [ "$TYPE" = "Bridge" ]; then
  109.                         bridgeinterfaces="$bridgeinterfaces $i"
  110.                         continue
  111.                 fi
  112.                 if [ "$TYPE" = "IPSEC" ]; then
  113.                         vpninterfaces="$vpninterfaces $i"
  114.                         continue
  115.                 fi
  117.                 if [ "${DEVICE%%.*}" != "$DEVICE"  -o  "${DEVICE##vlan}" != "$DEVICE" ] ; then
  118.                         vlaninterfaces="$vlaninterfaces $i"
  119.                         continue
  120.                 fi
  122.                 if LANG=C grep -EL "^ONBOOT=['\"]?[Nn][Oo]['\"]?" ifcfg-$i > /dev/null ; then
  123.                         # this loads the module, to preserve ordering
  124.                         is_available $i
  125.                         continue
  126.                 fi
  127.                 action $"Bringing up interface $i: " ./ifup $i boot
  128.                 [ $? -ne 0 ] && rc=1
  129.         done
  131.         # Bring up xDSL and VPN interfaces
  132.         for i in $vlaninterfaces $bridgeinterfaces $xdslinterfaces $vpninterfaces ; do
  133.             if ! LANG=C grep -EL "^ONBOOT=['\"]?[Nn][Oo]['\"]?" ifcfg-$i >/dev/null 2>&1 ; then
  134.                 action $"Bringing up interface $i: " ./ifup $i boot
  135.                 [ $? -ne 0 ] && rc=1
  136.             fi
  137.         done
  139.         # Add non interface-specific static-routes.
  140.         if [ -f /etc/sysconfig/static-routes ]; then
  141.            if [ -x /sbin/route ]; then
  142.                grep "^any" /etc/sysconfig/static-routes | while read ignore args ; do
  143.                    /sbin/route add -$args
  144.                done
  145.            else
  146.                net_log $"Legacy static-route support not available: /sbin/route not found"
  147.            fi
  148.         fi    
  150.         # IPv6 hook (post IPv4 start)
  151.         if [ -x /etc/sysconfig/network-scripts/init.ipv6-global ]; then
  152.                 /etc/sysconfig/network-scripts/init.ipv6-global start post
  153.         fi
  154.         # Run this again to catch any interface-specific actions
  155.         apply_sysctl
  157.         touch /var/lock/subsys/network
  159.         [ -n "${NETWORKDELAY}" ] && /bin/sleep ${NETWORKDELAY}
  160.         ;;
  161.   stop)
  162.         [ "$EUID" != "0" ] && exit 4
  163.         # Don't shut the network down if root is on NFS or a network
  164.         # block device.
  165.         rootfs=$(awk '{ if ($1 !~ /^[ \t]*#/ && $2 == "/" && $3 != "rootfs") { print $3; }}' /proc/mounts)
  166.         rootopts=$(awk '{ if ($1 !~ /^[ \t]*#/ && $2 == "/") { print $4; }}' /etc/mtab)
  168.         if [[ "$rootfs" == nfs* || "$rootopts" =~ _r?netdev ]] ; then
  169.                 exit 1
  170.         fi
  172.         systemctl show --property=RequiredBy -- -.mount | grep -q 'remote-fs.target' && exit 1
  174.         vlaninterfaces=""
  175.         vpninterfaces=""
  176.         xdslinterfaces=""
  177.         bridgeinterfaces=""
  178.         remaining=""
  179.         rc=0
  181.         # get list of bonding, vpn, and xdsl interfaces
  182.         for i in $interfaces; do
  183.                 unset DEVICE TYPE
  184.                 eval $(LANG=C grep -F "DEVICE=" ifcfg-$i)
  185.                 eval $(LANG=C grep -F "TYPE=" ifcfg-$i)
  187.                 if [ -z "$DEVICE" ] ; then DEVICE="$i"; fi
  189.                 if [ "${DEVICE##cipcb}" != "$DEVICE" ] ; then
  190.                         vpninterfaces="$vpninterfaces $i"
  191.                         continue
  192.                 fi
  193.                 if [ "$TYPE" = "IPSEC" ]; then
  194.                         vpninterfaces="$vpninterfaces $i"
  195.                         continue
  196.                 fi
  197.                 if [ "$TYPE" = "Bridge" ]; then
  198.                         bridgeinterfaces="$bridgeinterfaces $i"
  199.                         continue
  200.                 fi
  201.                 if [ "$TYPE" = "xDSL" ]; then
  202.                         xdslinterfaces="$xdslinterfaces $i"
  203.                         continue
  204.                 fi
  206.                 if [ "${DEVICE%%.*}" != "$DEVICE"  -o  "${DEVICE##vlan}" != "$DEVICE" ] ; then
  207.                         vlaninterfaces="$vlaninterfaces $i"
  208.                         continue
  209.                 fi
  210.                 remaining="$remaining $i"
  211.         done
  213.         for i in $vpninterfaces $xdslinterfaces $bridgeinterfaces $vlaninterfaces $remaining; do
  214.                 unset DEVICE TYPE
  215.                 (. ./ifcfg-$i
  216.                 if [ -z "$DEVICE" ] ; then DEVICE="$i"; fi
  218.                 if ! check_device_down $DEVICE; then
  219.                    action $"Shutting down interface $i: " ./ifdown $i boot
  220.                    [ $? -ne 0 ] && rc=1
  221.                 fi
  222.                 )
  223.         done
  225.         action $"Shutting down loopback interface: " ./ifdown ifcfg-lo
  227.         sysctl -w net.ipv4.ip_forward=0 > /dev/null 2>&1
  229.         # IPv6 hook (post IPv4 stop)
  230.         if [ -x /etc/sysconfig/network-scripts/init.ipv6-global ]; then
  231.                 /etc/sysconfig/network-scripts/init.ipv6-global stop post
  232.         fi
  234.         rm -f /var/lock/subsys/network
  235.         ;;
  236.   status)
  237.         echo $"Configured devices:"
  238.         echo lo $interfaces
  240.         echo $"Currently active devices:"
  241.         echo $(/sbin/ip -o link show up | awk -F ": " '{ print $2 }')
  242.         ;;
  243.   restart|reload|force-reload)
  244.         cd "$CWD"
  245.         $0 stop
  246.         $0 start
  247.         rc=$?
  248.         ;;
  249.   *)
  250.         echo $"Usage: $0 {start|stop|status|restart|reload|force-reload}"
  251.         exit 2
  252. esac
  254. exit $rc

服务运行级别

centos6祖先进程为init，使用init控制运行级别，centos7祖先进程改为systemd，自然也有init转变为systemd来管理运行级别

  1. [root@centos7 system]# chkconfig --list
  3. Note: This output shows SysV services only and does not include native
  4.       systemd services. SysV configuration data might be overridden by native
  5.       systemd configuration.
  7.       If you want to list systemd services use 'systemctl list-unit-files'.
  8.       To see services enabled on particular target use
  9.       'systemctl list-dependencies [target]'.
  11. aegis           0:off   1:off   2:on    3:on    4:on    5:on    6:off
  12. netconsole      0:off   1:off   2:off   3:off   4:off   5:off   6:off
  13. network         0:off   1:off   2:on    3:on    4:on    5:on    6:off
  14. [root@centos7 system]#
init 0 关机
init 1 单用户
init 2 不带网络模式多用户
init 3 字符模式多用户
init 4 未使用
init 5 图形界面多用户
init 6 重启

控制服务命令

  1. service network start  # 启动服务

systemctl

Centos 7之后使用，service的强化

  1. [root@centos7 init.d]# cd /usr/lib/systemd/system
  2. [root@centos7 system]# cat sshd.service

以下是sshd服务的启停脚本

  1. [Unit]
  2. Description=OpenSSH server daemon
  3. Documentation=man:sshd(8) man:sshd_config(5)
  4. After=network.target sshd-keygen.service hschen.service  # 增加一个hschen.service
  5. Requires=hschen.service  #在 sshd服务之前启动
  6. Wants=sshd-keygen.service
  8. [Service]
  9. Type=notify
  10. EnvironmentFile=/etc/sysconfig/sshd  # 配置文件
  11. ExecStart=/usr/sbin/sshd -D $OPTIONS  # 启动
  12. ExecReload=/bin/kill -HUP $MAINPID
  13. KillMode=process
  14. Restart=on-failure  # 重启
  15. RestartSec=42s
  16. RestartPreventExitStatus=255
  18. [Install]
  19. WantedBy=multi-user.target  # 默认在多用户运行级别下引导

运行级别

.service 表示服务 .target 表示运行级别

  1. [root@centos7 ~]# cd /lib/systemd/system
  2. [root@centos7 system]# ll
  3. total 944
  4. -rw-r--r--  1 root root  275 Jun 10  2014 arp-ethers.service
  5. -rw-r--r--  1 root root  222 Nov  6  2016 atd.service
  6. -rw-r--r--  1 root root  947 Mar  3  2017 auditd.service
  7. lrwxrwxrwx  1 root root   14 Aug 18  2017 autovt@.service -> getty@.service
  8. -rw-r--r--  1 root root  517 May 26  2017 basic.target
  9. drwxr-xr-x. 2 root root 4096 Aug 18  2017 basic.target.wants
  10. -r--r--r--  1 root root  383 Jun 29  2017 blk-availability.service
  11. -rw-r--r--  1 root root  379 May 26  2017 bluetooth.target
  12. -rw-r--r--  1 root root  160 Sep 12  2016 brandbot.path
  13. ... ...
  1. [root@centos7 system]# ll runlevel*.target
  2. lrwxrwxrwx 1 root root 15 Aug 18  2017 runlevel0.target -> poweroff.target
  3. lrwxrwxrwx 1 root root 13 Aug 18  2017 runlevel1.target -> rescue.target  # 救援模式
  4. lrwxrwxrwx 1 root root 17 Aug 18  2017 runlevel2.target -> multi-user.target
  5. lrwxrwxrwx 1 root root 17 Aug 18  2017 runlevel3.target -> multi-user.target
  6. lrwxrwxrwx 1 root root 17 Aug 18  2017 runlevel4.target -> multi-user.target
  7. lrwxrwxrwx 1 root root 16 Aug 18  2017 runlevel5.target -> graphical.target
  8. lrwxrwxrwx 1 root root 13 Aug 18  2017 runlevel6.target -> reboot.target
  9. [root@centos7 system]#

查看当前运行级别 & 设置下一次开机运行级别

  1. [root@centos7 system]# systemctl get-default
  2. multi-user.target
  4. [root@centos7 system]# systemctl set-default multi-user.target
  5. Removed symlink /etc/systemd/system/default.target.
  6. Created symlink from /etc/systemd/system/default.target to /usr/lib/systemd/system/multi-user.target.
  7. [root@centos7 system]#

控制服务

  1. systemctl start|stop|restart|reload|enable|disable|status sshd.service

系统日志

image.png

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标志内核运行信息
image.png

系统安全日志
image.png

日常任务进程
image.png