系统日志分析

时间:2024-04-14 22:58:58

                                                                                      系统日志分析

 

 

案例3:系统日志分析

3.1 问题

本例要求熟悉Linux系统中的常见日志文件,使用必要的命令工具完成下列任务:

  1. 列出所有包含关键词8909的系统日志消息
  2. 查看启动时识别的鼠标设备信息
  3. 列出最近2条成功/不成功的用户登录消息
  4. 列出最近10条重要程度在 ERR 及以上的日志消息
  5. 列出所有与服务httpd相关的消息
  6. 列出前4个小时内新记录的日志

3.2 方案

常见的系统日志及各自用途:

  • /var/log/messages,记录内核消息、各种服务的公共消息
  • /var/log/dmesg,记录系统启动过程的各种消息
  • /var/log/cron,记录与cron计划任务相关的消息
  • /var/log/maillog,记录邮件收发相关的消息
  • /var/log/secure,记录与访问限制相关的安全消息

日志消息的优先级(高-->低):

  • EMERG(紧急):级别0,系统不可用的情况
  • ALERT(警报):级别1,必须马上采取措施的情况
  • CRIT(严重):级别2,严重情形
  • ERR(错误):级别3,出现错误
  • WARNING(警告):级别4,值得警告的情形
  • NOTICE(注意):级别5,普通但值得引起注意的事件
  • INFO(信息):级别6,一般信息
  • DEBUG(调试):级别7,程序/服务调试消息

RHEL7提供的journalctl日志工具的常见用法:

  • journalctl | grep 关键词
  • journalctl -u 服务名 -p 优先级
  • journalctl -n 消息条数
  • journalctl --since="yyyy-mm-dd HH:MM:SS" --until="yyyy-mm-dd HH:MM:SS"

3.3 步骤

实现此案例需要按照如下步骤进行。

步骤一:分析系统日志及用户日志

1)列出所有包含关键词8909的系统日志消息

简单模拟一个故障(SELinux阻止Web开放8909端口):

  1. [root@svr7 ~]# vim  /etc/httpd/conf.d/8909.conf          //添加开8909端口配置
  2. Listen 8909
  3. [root@svr7 ~]# setenforce 1                             //开启强制模式
  4. [root@svr7 ~]# systemctl  restart  httpd                 //起服务失败
  5. Job for httpd.service failed because the control process exited with error code. See "systemctl status httpd.service" and "journalctl -xe" for details.

从日志文件/var/log/messages中检索信息:

  1. [root@svr7 ~]# grep  8909  /var/log/messages
  2. Jan  6 17:53:48 svr7 setroubleshoot: SELinux is preventing /usr/sbin/httpd from name_bind access on the tcp_socket port 8909. For complete SELinux messages. run sealert -l 6d37b8f0-ab8a-4082-9295-c784f4f57190
  3. Jan  6 17:53:48 svr7 python: SELinux is preventing /usr/sbin/httpd from name_bind access on the tcp_socket port 8909.#012#012*****  Plugin bind_ports (92.2 confidence) suggests   ************************#012#012If you want to allow /usr/sbin/httpd to bind to network port 8909#012Then you need to modify the port type.#012Do#012# semanage port -a -t PORT_TYPE -p tcp 8909#012    where PORT_TYPE is one of the following: http_cache_port_t, http_port_t, jboss_management_port_t, jboss_messaging_port_t, ntop_port_t, puppet_port_t.#012#012*****  Plugin catchall_boolean (7.83 confidence) suggests   ******************#012#012If you want to allow nis to enabled#012Then you must tell SELinux about this by enabling the \'nis_enabled\' boolean.#012#012Do#012setsebool -P nis_enabled 1#012#012*****  Plugin catchall (1.41 confidence) suggests   **************************#012#012If you believe that httpd should be allowed name_bind access on the port 8909 tcp_socket by default.#012Then you should report this as a bug.#012You can generate a local policy module to allow this access.#012Do#012allow this access for now by executing:#012# grep httpd /var/log/audit/audit.log | audit2allow -M mypol#012# semodule -i mypol.pp#012
  4. .. ..

使用完毕记得删除测试配置文件:

  1. [root@svr7 ~]# rm  -rf  /etc/httpd/conf.d/8909.conf
  2. [root@svr7 ~]# systemctl  restart  httpd

2)查看启动时识别的鼠标设备信息

  1. [root@svr7 ~]# dmesg  |  grep  -i  mouse
  2. [    1.020385] mousedev: PS/2 mouse device common for all mice
  3. [    1.249422] input: ImPS/2 Generic Wheel Mouse as /devices/platform/i8042/serio1/input/input2
  4. [    2.279665] usb 2-1: Product: VMware Virtual USB Mouse
  5. [    2.603999] input: VMware VMware Virtual USB Mouse as /devices/pci0000:00/0000:00:11.0/0000:02:00.0/usb2/2-1/2-1:1.0/input/input3
  6. [    2.604222] hid-generic 0003:0E0F:0003.0001: input,hidraw0: USB HID v1.10 Mouse [VMware VMware Virtual USB Mouse] on usb-0000:02:00.0-1/input0

3)列出最近2条成功/不成功的用户登录消息

查看成功登录的事件消息:

  1. [root@svr7 ~]# last  -2
  2. zhsan    pts/2        192.168.4.207    Fri Jan  6 18:00 - 18:00  (00:00)    
  3. root     pts/2        192.168.4.110    Fri Jan  6 17:26 - 17:59  (00:33)    
  4. wtmp begins Thu Aug  4 00:10:16 2016

查看失败登录的事件消息:

  1. [root@svr7 ~]# lastb  -2
  2. anonymou ssh:notty    192.168.4.207    Fri Jan  6 18:00 - 18:00  (00:00)    
  3. anonymou ssh:notty    192.168.4.207    Fri Jan  6 18:00 - 18:00  (00:00)    
  4. btmp begins Fri Jan  6 18:00:34 2017

步骤二:使用journalctl日志提取工具

1)列出最近10条重要程度在 ERR 及以上的日志消息

  1. [root@svr7 ~]# journalctl  -p err  -n  10
  2. -- Logs begin at Thu 2017-01-05 15:50:08 CST, end at Fri 2017-01-06 18:01:01 CST. --
  3. Jan 06 14:56:57 svr7 setroubleshoot[23702]: SELinux is preventing /usr/sbin/vsftpd from getattr access on the file /rhel7/repodata/repomd.xml. For complete SELinux mes
  4. Jan 06 14:56:57 svr7 setroubleshoot[23702]: SELinux is preventing /usr/sbin/vsftpd from read access on the file repomd.xml. For complete SELinux messages. run sealert
  5. Jan 06 14:56:57 svr7 setroubleshoot[23702]: SELinux is preventing /usr/sbin/vsftpd from read access on the file repomd.xml. For complete SELinux messages. run sealert
  6. Jan 06 14:56:57 svr7 setroubleshoot[23702]: SELinux is preventing /usr/sbin/vsftpd from lock access on the file /rhel7/repodata/repomd.xml. For complete SELinux messag
  7. Jan 06 17:53:48 svr7 setroubleshoot[33743]: Plugin Exception restorecon_source
  8. Jan 06 17:53:48 svr7 setroubleshoot[33743]: SELinux is preventing /usr/sbin/httpd from name_bind access on the tcp_socket port 8909. For complete SELinux messages. run
  9. Jan 06 17:53:53 svr7 setroubleshoot[33743]: SELinux is preventing /usr/sbin/httpd from name_connect access on the tcp_socket port 8909. For complete SELinux messages. 
  10. Jan 06 17:53:54 svr7 systemd[1]: Failed to start The Apache HTTP Server.
  11. .. ..
  12. lines 1-11/11 (END)

2)列出所有与服务httpd相关的消息

  1. [root@svr7 ~]# journalctl   -u  httpd
  2. -- Logs begin at Thu 2017-01-05 15:50:08 CST, end at Fri 2017-01-06 18:01:01 CST. --
  3. Jan 06 14:57:16 svr7 systemd[1]: Starting The Apache HTTP Server...
  4. Jan 06 14:57:16 svr7 httpd[23812]: AH00557: httpd: apr_sockaddr_info_get() failed for svr7
  5. Jan 06 14:57:16 svr7 httpd[23812]: AH00558: httpd: Could not reliably determine the server\'s fully qualified domain name, using 127.0.0.1. Set the \'ServerName\' directi
  6. Jan 06 14:57:16 svr7 systemd[1]: Started The Apache HTTP Server.
  7. Jan 06 17:53:44 svr7 systemd[1]: Stopping The Apache HTTP Server...
  8. Jan 06 17:53:46 svr7 systemd[1]: Starting The Apache HTTP Server...
  9. Jan 06 17:53:46 svr7 httpd[33741]: AH00557: httpd: apr_sockaddr_info_get() failed for svr7
  10. .. ..

3)列出前4个小时内新记录的日志

根据当前日期时间往前推4个小时,确定--since起始和--until结束时刻:

  1. [root@svr7 ~]# journalctl  --since  "2017-01-06 14:11"  --until  "2017-01-06 18:11"
  2. -- Logs begin at Thu 2017-01-05 15:50:08 CST, end at Fri 2017-01-06 18:10:01 CST. --
  3. Jan 06 14:20:01 svr7 systemd[1]: Started Session 160 of user root.
  4. Jan 06 14:20:01 svr7 CROND[22869]: (root) CMD (/usr/lib64/sa/sa1 1 1)
  5. Jan 06 14:20:01 svr7 systemd[1]: Starting Session 160 of user root.
  6. Jan 06 14:30:01 svr7 systemd[1]: Started Session 161 of user root.
  7. Jan 06 14:30:01 svr7 CROND[23028]: (root) CMD (/usr/lib64/sa/sa1 1 1)
  8. Jan 06 14:31:39 svr7 systemd[1]: Starting Session 162 of user root.
  9. Jan 06 14:32:17 svr7 sshd[23046]: pam_unix(sshd:session): session closed for user root
  10. Jan 06 14:31:39 svr7 systemd[1]: Started Session 162 of user root.
  11. Jan 06 14:31:39 svr7 sshd[23046]: pam_unix(sshd:session): session opened for user root by (uid=0)
  12. Jan 06 14:31:39 svr7 systemd-logind[985]: New session 162 of user root.
  13. .. .