Linux访问权限控制及时间同步实践
客户机上也需要安装chrony软件和运行其服务，当然客户端也可以安装ntp软件包，用ntpdate 加时间服务器地址来同步时间；用ntpdate + 时间服务器地址同步时间简单粗暴，这种方式同步时间实际上是将服务器时间跳到当前时间，中间有一段空白段，强烈不建议这样同步时间。
1、编写脚本/root/bin/checkip.sh，每5分钟检查一次，如果发现通过ssh登录失败 次数超过10次，自动将此远程IP放入Tcp Wrapper的黑名单中予以禁止防问
方式一：脚本+定时任务
1）编写脚本
[root@test ~]#cat checkip.sh
#!/bin/bash
#
#************************************************************************
#Author: qiuhom
#QQ: 467697313
#mail: qiuhom467697313@qq.com
#Date: 2019-12-22
#FileName： checkip.sh
#URL: https://www.cnblogs.com/qiuhom-1874/
#Description：
#Copyright (C): 2019 All rights reserved
#************************************************************************
[ $UID -ne 0 ]&&echo "this script must root run it " && exit 1
if [[ ! -e "/work" ]]; then
mkdir /work
fi
cmd=`cat /var/log/secure|grep "Failed password for qiuhom"|awk '{print $(NF-3)}'|sort|uniq -c|awk '{print $2"==>"$1}'`
echo "$cmd">/work/ip.txt
for i in `cat /work/ip.txt`
do
ip=`echo "$i"|awk -F "==>" '{print $1}'`
count=`echo "$i"|awk -F "==>" '{print $2}'`
if [ $count -gt 10 ];then
xx=`grep $ip /etc/hosts.deny |wc -l`
if [ $xx == 0 ];then
echo "ALL:$ip" >> /etc/hosts.deny
fi
fi
done
[root@test ~]#
说明：此脚本主要思想是通过日志来过滤出登录失败的用户，然后取出其ip地址，统计其ip出现的次数，如果登录失败10次，则把其ip放入/etc/hosts.deny（TCP Warpper的黑名单）中将其ip禁用。
2）指定计划任务
[root@test ~]#crontab -l */5 * * * * bash /root/bin/checkip.sh &> /dev/null
方式二：脚本方式，死循环加sleep 来控制执行时长周期
[root@test ~]#cat checkip.sh
#!/bin/bash
#
#************************************************************************
#Author: qiuhom
#QQ: 467697313
#mail: qiuhom467697313@qq.com
#Date: 2019-12-22
#FileName： checkip.sh
#URL: https://www.cnblogs.com/qiuhom-1874/
#Description：
#Copyright (C): 2019 All rights reserved
#************************************************************************
[ $UID -ne 0 ]&&echo "this script must root run it " && exit 1
if [[ ! -e "/work" ]]; then
mkdir /work
fi
while true
do
sleep 300
cmd=`cat /var/log/secure|grep "Failed password for qiuhom"|awk '{print $(NF-3)}'|sort|uniq -c|awk '{print $2"==>"$1}'`
echo "$cmd">/work/ip.txt
for i in `cat /work/ip.txt`
do
ip=`echo "$i"|awk -F "==>" '{print $1}'`
count=`echo "$i"|awk -F "==>" '{print $2}'`
if [ $count -gt 10 ];then
xx=`grep $ip /etc/hosts.deny |wc -l`
if [ $xx == 0 ];then
echo "ALL:$ip" >> /etc/hosts.deny
fi
fi
done
done
[root@test ~]#
2、配置magedu用户的sudo权限，允许magedu用户拥有root权限
方式一：将magedu用户加入到wheel组中，不改动其/etc/sudoers文件
[root@test ~]#id magedu uid=1004(magedu) gid=1004(magedu) 组=1004(magedu) [root@test ~]# [root@test ~]#id magedu uid=1004(magedu) gid=1004(magedu) 组=1004(magedu) [root@test ~]#su - magedu 上一次登录：日 12月 22 13:52:50 CST 2019pts/0 上 [magedu@test ~]$cat /etc/sudoers cat: /etc/sudoers: 权限不够 [magedu@test ~]$su - 密码： 上一次登录：日 12月 22 13:26:01 CST 2019pts/0 上 [root@test ~]#usermod -aG wheel magedu [root@test ~]#id magedu uid=1004(magedu) gid=1004(magedu) 组=1004(magedu),10(wheel) [root@test ~]#su - magedu 上一次登录：日 12月 22 13:55:04 CST 2019pts/0 上 [magedu@test ~]$cat /etc/sudoers cat: /etc/sudoers: 权限不够 [magedu@test ~]$sudo cat /etc/sudoers ## Sudoers allows particular users to run various commands as ## the root user, without needing the root password. ## ## Examples are provided at the bottom of the file for collections ## of related commands, which can then be delegated out to particular ## users or groups. ## ## This file must be edited with the 'visudo' command. ## Host Aliases ## Groups of machines. You may prefer to use hostnames (perhaps using ## wildcards for entire domains) or IP addresses instead. # Host_Alias FILESERVERS = fs1, fs2 # Host_Alias MAILSERVERS = smtp, smtp2 ## User Aliases ## These aren't often necessary, as you can use regular groups ## (ie, from files, LDAP, NIS, etc) in this file - just use %groupname ## rather than USERALIAS # User_Alias ADMINS = jsmith, mikem ## Command Aliases ## These are groups of related commands... ## Networking # Cmnd_Alias NETWORKING = /sbin/route, /sbin/ifconfig, /bin/ping, /sbin/dhclient, /usr/bin/net, /sbin/iptables, /usr/bin/rfcomm, /usr/bin/wvdial, /sbin/iwconfig, /sbin/mii-tool ## Installation and management of software # Cmnd_Alias SOFTWARE = /bin/rpm, /usr/bin/up2date, /usr/bin/yum ## Services # Cmnd_Alias SERVICES = /sbin/service, /sbin/chkconfig, /usr/bin/systemctl start, /usr/bin/systemctl stop, /usr/bin/systemctl reload, /usr/bin/systemctl restart, /usr/bin/systemctl status, /usr/bin/systemctl enable, /usr/bin/systemctl disable ## Updating the locate database # Cmnd_Alias LOCATE = /usr/bin/updatedb ## Storage # Cmnd_Alias STORAGE = /sbin/fdisk, /sbin/sfdisk, /sbin/parted, /sbin/partprobe, /bin/mount, /bin/umount ## Delegating permissions # Cmnd_Alias DELEGATING = /usr/sbin/visudo, /bin/chown, /bin/chmod, /bin/chgrp ## Processes # Cmnd_Alias PROCESSES = /bin/nice, /bin/kill, /usr/bin/kill, /usr/bin/killall ## Drivers # Cmnd_Alias DRIVERS = /sbin/modprobe # Defaults specification # # Refuse to run if unable to disable echo on the tty. # Defaults !visiblepw # # Preserving HOME has security implications since many programs # use it when searching for configuration files. Note that HOME # is already set when the the env_reset option is enabled, so # this option is only effective for configurations where either # env_reset is disabled or HOME is present in the env_keep list. # Defaults always_set_home Defaults match_group_by_gid # Prior to version 1.8.15, groups listed in sudoers that were not # found in the system group database were passed to the group # plugin, if any. Starting with 1.8.15, only groups of the form # %:group are resolved via the group plugin by default. # We enable always_query_group_plugin to restore old behavior. # Disable this option for new behavior. Defaults always_query_group_plugin Defaults env_reset Defaults env_keep = "COLORS DISPLAY HOSTNAME HISTSIZE KDEDIR LS_COLORS" Defaults env_keep += "MAIL PS1 PS2 QTDIR USERNAME LANG LC_ADDRESS LC_CTYPE" Defaults env_keep += "LC_COLLATE LC_IDENTIFICATION LC_MEASUREMENT LC_MESSAGES" Defaults env_keep += "LC_MONETARY LC_NAME LC_NUMERIC LC_PAPER LC_TELEPHONE" Defaults env_keep += "LC_TIME LC_ALL LANGUAGE LINGUAS _XKB_CHARSET XAUTHORITY" # # Adding HOME to env_keep may enable a user to run unrestricted # commands via sudo. # # Defaults env_keep += "HOME" Defaults secure_path = /sbin:/bin:/usr/sbin:/usr/bin ## Next comes the main part: which users can run what software on ## which machines (the sudoers file can be shared between multiple ## systems). ## Syntax: ## ## user MACHINE=COMMANDS ## ## The COMMANDS section may have other options added to it. ## ## Allow root to run any commands anywhere root ALL=(ALL) ALL qiuhom ALL=(ALL) ALL ## Allows members of the 'sys' group to run networking, software, ## service management apps and more. # %sys ALL = NETWORKING, SOFTWARE, SERVICES, STORAGE, DELEGATING, PROCESSES, LOCATE, DRIVERS ## Allows people in group wheel to run all commands %wheel ALL=(ALL) ALL ## Same thing without a password # %wheel ALL=(ALL) NOPASSWD: ALL ## Allows members of the users group to mount and unmount the ## cdrom as root # %users ALL=/sbin/mount /mnt/cdrom, /sbin/umount /mnt/cdrom ## Allows members of the users group to shutdown this system # %users localhost=/sbin/shutdown -h now ## Read drop-in files from /etc/sudoers.d (the # here does not mean a comment) #includedir /etc/sudoers.d [magedu@test ~]$
说明：此方式能行的原因是/etc/sudoers文件中配置了wheel组允许在其组里的成员运行所有命令
方式二：将magedu用户配置成能够代替root用户做任何事情
[magedu@test ~]$su - 密码： 上一次登录：日 12月 22 13:55:26 CST 2019pts/0 上 [root@test ~]#usermod -G magedu magedu [root@test ~]#id magedu uid=1004(magedu) gid=1004(magedu) 组=1004(magedu) [root@test ~]#echo "magedu ALL=(root) ALL" >> /etc/sudoers [root@test ~]#tail /etc/sudoers ## Allows members of the users group to mount and unmount the ## cdrom as root # %users ALL=/sbin/mount /mnt/cdrom, /sbin/umount /mnt/cdrom ## Allows members of the users group to shutdown this system # %users localhost=/sbin/shutdown -h now ## Read drop-in files from /etc/sudoers.d (the # here does not mean a comment) #includedir /etc/sudoers.d magedu ALL=(root) ALL [root@test ~]#su - magedu 上一次登录：日 12月 22 13:55:49 CST 2019pts/0 上 [magedu@test ~]$cat /etc/sudoers cat: /etc/sudoers: 权限不够 [magedu@test ~]$sudo cat /etc/sudoers [sudo] magedu 的密码： ## Sudoers allows particular users to run various commands as ## the root user, without needing the root password. ## ## Examples are provided at the bottom of the file for collections ## of related commands, which can then be delegated out to particular ## users or groups. ## ## This file must be edited with the 'visudo' command. ## Host Aliases ## Groups of machines. You may prefer to use hostnames (perhaps using ## wildcards for entire domains) or IP addresses instead. # Host_Alias FILESERVERS = fs1, fs2 # Host_Alias MAILSERVERS = smtp, smtp2 ## User Aliases ## These aren't often necessary, as you can use regular groups ## (ie, from files, LDAP, NIS, etc) in this file - just use %groupname ## rather than USERALIAS # User_Alias ADMINS = jsmith, mikem ## Command Aliases ## These are groups of related commands... ## Networking # Cmnd_Alias NETWORKING = /sbin/route, /sbin/ifconfig, /bin/ping, /sbin/dhclient, /usr/bin/net, /sbin/iptables, /usr/bin/rfcomm, /usr/bin/wvdial, /sbin/iwconfig, /sbin/mii-tool ## Installation and management of software # Cmnd_Alias SOFTWARE = /bin/rpm, /usr/bin/up2date, /usr/bin/yum ## Services # Cmnd_Alias SERVICES = /sbin/service, /sbin/chkconfig, /usr/bin/systemctl start, /usr/bin/systemctl stop, /usr/bin/systemctl reload, /usr/bin/systemctl restart, /usr/bin/systemctl status, /usr/bin/systemctl enable, /usr/bin/systemctl disable ## Updating the locate database # Cmnd_Alias LOCATE = /usr/bin/updatedb ## Storage # Cmnd_Alias STORAGE = /sbin/fdisk, /sbin/sfdisk, /sbin/parted, /sbin/partprobe, /bin/mount, /bin/umount ## Delegating permissions # Cmnd_Alias DELEGATING = /usr/sbin/visudo, /bin/chown, /bin/chmod, /bin/chgrp ## Processes # Cmnd_Alias PROCESSES = /bin/nice, /bin/kill, /usr/bin/kill, /usr/bin/killall ## Drivers # Cmnd_Alias DRIVERS = /sbin/modprobe # Defaults specification # # Refuse to run if unable to disable echo on the tty. # Defaults !visiblepw # # Preserving HOME has security implications since many programs # use it when searching for configuration files. Note that HOME # is already set when the the env_reset option is enabled, so # this option is only effective for configurations where either # env_reset is disabled or HOME is present in the env_keep list. # Defaults always_set_home Defaults match_group_by_gid # Prior to version 1.8.15, groups listed in sudoers that were not # found in the system group database were passed to the group # plugin, if any. Starting with 1.8.15, only groups of the form # %:group are resolved via the group plugin by default. # We enable always_query_group_plugin to restore old behavior. # Disable this option for new behavior. Defaults always_query_group_plugin Defaults env_reset Defaults env_keep = "COLORS DISPLAY HOSTNAME HISTSIZE KDEDIR LS_COLORS" Defaults env_keep += "MAIL PS1 PS2 QTDIR USERNAME LANG LC_ADDRESS LC_CTYPE" Defaults env_keep += "LC_COLLATE LC_IDENTIFICATION LC_MEASUREMENT LC_MESSAGES" Defaults env_keep += "LC_MONETARY LC_NAME LC_NUMERIC LC_PAPER LC_TELEPHONE" Defaults env_keep += "LC_TIME LC_ALL LANGUAGE LINGUAS _XKB_CHARSET XAUTHORITY" # # Adding HOME to env_keep may enable a user to run unrestricted # commands via sudo. # # Defaults env_keep += "HOME" Defaults secure_path = /sbin:/bin:/usr/sbin:/usr/bin ## Next comes the main part: which users can run what software on ## which machines (the sudoers file can be shared between multiple ## systems). ## Syntax: ## ## user MACHINE=COMMANDS ## ## The COMMANDS section may have other options added to it. ## ## Allow root to run any commands anywhere root ALL=(ALL) ALL qiuhom ALL=(ALL) ALL ## Allows members of the 'sys' group to run networking, software, ## service management apps and more. # %sys ALL = NETWORKING, SOFTWARE, SERVICES, STORAGE, DELEGATING, PROCESSES, LOCATE, DRIVERS ## Allows people in group wheel to run all commands %wheel ALL=(ALL) ALL ## Same thing without a password # %wheel ALL=(ALL) NOPASSWD: ALL ## Allows members of the users group to mount and unmount the ## cdrom as root # %users ALL=/sbin/mount /mnt/cdrom, /sbin/umount /mnt/cdrom ## Allows members of the users group to shutdown this system # %users localhost=/sbin/shutdown -h now ## Read drop-in files from /etc/sudoers.d (the # here does not mean a comment) #includedir /etc/sudoers.d magedu ALL=(root) ALL [magedu@test ~]$
说明：以上方式就是把magedu用户配置成能够以root身份执行所有命令
4、配置chrony服务，实现服务器时间自动同步
1）安装chrony服务
yum install chrony -y
说明：ntp作为时间同步的服务器软件和客户端软件它都必须运行成守护进程，用ntp作为服务器软件有个缺陷就是同步时间周期很长，所以此实验是chrony作为客户端软件和服务器软件，它比ntp更加精准，其同步周期较短。
2）配置chrony.conf 允许其运行为时间服务器并允许内网网段来同步时间并启动服务
[root@test ~]#cat /etc/chrony.conf # Use public servers from the pool.ntp.org project. # Please consider joining the pool (http://www.pool.ntp.org/join.html). #server 0.centos.pool.ntp.org iburst #server 1.centos.pool.ntp.org iburst #server 2.centos.pool.ntp.org iburst server 3.centos.pool.ntp.org iburst # Record the rate at which the system clock gains/losses time. driftfile /var/lib/chrony/drift # Allow the system clock to be stepped in the first three updates # if its offset is larger than 1 second. makestep 1.0 3 # Enable kernel synchronization of the real-time clock (RTC). rtcsync # Enable hardware timestamping on all interfaces that support it. #hwtimestamp * # Increase the minimum number of selectable sources required to adjust # the system clock. #minsources 2 # Allow NTP client access from local network. allow 192.168.0.0/16 # Serve time even if not synchronized to a time source. #local stratum 10 # Specify file containing keys for NTP authentication. #keyfile /etc/chrony.keys # Specify directory for log files. logdir /var/log/chrony # Select which information is logged. #log measurements statistics tracking [root@test ~]#
说明：server：时间服务器地址 ，allow后面跟允许客户端地址/子网掩码 或者直接配置成allow all 则表示允许所有客户端来同步时间
systemctl start chronyd
说明：启动chronyd服务后，此时就可以用该服务器作为时间同步服务器，我们可以用chronyc这个工具来查看当前的时间服务器上从那个服务器同步时间的；chronyd默认监听在UDP的123端口和323端口
[root@test ~]#ss -nulp
State Recv-Q Send-Q Local Address:Port Peer Address:Port
UNCONN 0 0 *:123 *:* users:(("chronyd",pid=17074,fd=7))
UNCONN 0 0 127.0.0.1:323 *:* users:(("chronyd",pid=17074,fd=5))
UNCONN 0 0 ::1:323 :::* users:(("chronyd",pid=17074,fd=6))
[root@test ~]#
[root@test ~]#chronyc sources -v
210 Number of sources = 1
.-- Source mode '^' = server, '=' = peer, '#' = local clock.
/ .- Source state '*' = current synced, '+' = combined , '-' = not combined,
| / '?' = unreachable, 'x' = time may be in error, '~' = time too variable.
|| .- xxxx [ yyyy ] +/- zzzz
|| Reachability register (octal) -. | xxxx = adjusted offset,
|| Log2(Polling interval) --. | | yyyy = measured offset,
|| \ | | zzzz = estimated error.
|| | | \
MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================
^* sv1.ggsrv.de 2 7 377 10 -361us[ -538us] +/- 128ms
[root@test ~]#chronyc sourcestats -v
210 Number of sources = 1
.- Number of sample points in measurement set.
/ .- Number of residual runs with same sign.
| / .- Length of measurement set (time).
| | / .- Est. clock freq error (ppm).
| | | / .- Est. error in freq.
| | | | / .- Est. offset.
| | | | | | On the -.
| | | | | | samples. \
| | | | | | |
Name/IP Address NP NR Span Frequency Freq Skew Offset Std Dev
==============================================================================
sv1.ggsrv.de 22 12 22m -0.040 2.784 -937ns 1441us
[root@test ~]#
说明：可以看到当前chrony作为客户端是从互联网sv1.ggsrv.de服务器上同步时间的；chronyc 是一个交互工具，它可查看时间服务器的状态以及管理实践服务器，它有很多子命令，其帮助信息可以通过chronyc help 命令查看
3）配置客户端，并指定其服务器地址为刚才我们搭建的时间服务器地址
[root@test ~]#yum info chrony
Loaded plugins: fastestmirror, security
Determining fastest mirrors
* base: mirrors.aliyun.com
* extras: mirrors.aliyun.com
* updates: mirrors.aliyun.com
base | 3.7 kB 00:00
epel | 5.3 kB 00:00
epel/primary_db | 6.1 MB 00:01
extras | 3.4 kB 00:00
extras/primary_db | 29 kB 00:00
updates | 3.4 kB 00:00
updates/primary_db | 7.5 MB 00:02
Available Packages
Name : chrony
Arch : x86_64
Version : 2.1.1
Release : 2.el6_8
Size : 266 k
Repo : base
Summary : An NTP client/server
URL : http://chrony.tuxfamily.org
License : GPLv2
Description : A client/server for the Network Time Protocol, this program keeps your
: computer's clock accurate. It was specially designed to support
: systems with intermittent internet connections, but it also works well
: in permanently connected environments. It can use also hardware reference
: clocks, system real-time clock or manual input as time references.
[root@test ~]#yum install chrony -y
Loaded plugins: fastestmirror, security
Setting up Install Process
Loading mirror speeds from cached hostfile
base: mirrors.aliyun.com
* extras: mirrors.aliyun.com
* updates: mirrors.aliyun.com
Resolving Dependencies
There are unfinished transactions remaining. You might consider running yum-complete-transaction first to finish them.
--> Running transaction check
---> Package chrony.x86_64 0:2.1.1-2.el6_8 will be installed
--> Finished Dependency Resolution
Dependencies Resolved
=====================================================================================================================
Package Arch Version Repository Size
=====================================================================================================================
Installing:
chrony x86_64 2.1.1-2.el6_8 base 266 k
Transaction Summary
=====================================================================================================================
Install 1 Package(s)
Total download size: 266 k
Installed size: 453 k
Downloading Packages:
chrony-2.1.1-2.el6_8.x86_64.rpm | 266 kB 00:00
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
Installing : chrony-2.1.1-2.el6_8.x86_64 1/1
Verifying : chrony-2.1.1-2.el6_8.x86_64 1/1
Installed:
chrony.x86_64 0:2.1.1-2.el6_8
Complete!
[root@test ~]#vim /etc/chrony.conf
# Use public servers from the pool.ntp.org project.
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
#server 0.rhel.pool.ntp.org iburst
#server 1.rhel.pool.ntp.org iburst
#server 2.rhel.pool.ntp.org iburst
#server 3.rhel.pool.ntp.org iburst
server 192.168.0.99
# Ignore stratum in source selection.
stratumweight 0
# Record the rate at which the system clock gains/losses time.
driftfile /var/lib/chrony/drift
# In first three updates step the system clock instead of slew
# if the adjustment is larger than 10 seconds.
makestep 10 3
# Enable kernel synchronization of the real-time clock (RTC).
rtcsync
# Allow NTP client access from local network.
#allow 192.168/16
# Serve time even if not synchronized to any NTP server.
#local stratum 10
# Specify file containing keys for NTP and command authentication.
keyfile /etc/chrony.keys
# Specify key number for command authentication.
commandkey 1
# Generate new command key on start if missing.
generatecommandkey
# Disable logging of client accesses.
noclientlog
# Send message to syslog when clock adjustment is larger than 0.5 seconds.
"/etc/chrony.conf" 46L, 1272C written
[root@test ~]#
说明：客户机上也需要安装chrony软件和运行其服务，当然客户端也可以安装ntp软件包，用ntpdate 加时间服务器地址来同步时间；用ntpdate + 时间服务器地址同步时间简单粗暴，这种方式同步时间实际上是将服务器时间跳到当前时间，中间有一段空白段，强烈不建议这样同步时间。
[root@test ~]#date Thu Dec 12 12:14:08 CST 2019 [root@test ~]#chronyc sources 210 Number of sources = 1 MS Name/IP address Stratum Poll Reach LastRx Last sample =============================================================================== ^* 192.168.0.99 3 6 17 3 -21us[-14582m] +/- 131ms [root@test ~]#date Sun Dec 22 15:16:15 CST 2019
[root@test ~]#date -s "20191212 12:12:00" Thu Dec 12 12:12:00 CST 2019 [root@test ~]#date Thu Dec 12 12:12:02 CST 2019 [root@test ~]#ntpdate 192.168.0.99 22 Dec 15:18:15 ntpdate[3911]: step time server 192.168.0.99 offset 875161.922491 sec [root@test ~]#date Sun Dec 22 15:18:17 CST 2019 [root@test ~]#
5、实现cobbler+pxe自动化装机
详情请参考本人博客https://www.cnblogs.com/qiuhom-1874/p/12081310.html
作者：Linux-1874
本文版权归作者和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利.
