本例要求熟悉Linux系统中常见日志文件，使用必要的命令工具完成下列任务：
列出所有包含关键词8909的系统日志消息查看启动时识别的鼠标设备信息列出最近2条成功/不成功的用户登录消息列出最贱10条重要程度在ERR及以上的日志消息列出所有于服务httpd相关的消息列出前4个小时内新纪录的日志常见的系统日志及各自用途：
/var/log/messages，记录内核消息、各种服务的公认消息/var/og/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journactl -n 消息条数journalctl --since="yyyy-mm-dd HH:MM:SS" --until="yyyy-mm-dd HH:MM:SS"实现此案例需要按如下步骤进行。
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）：
[root@svr7 ~]# vim /etc/httpd/conf.d/8909.conf //添加开8909端口配置 Listen 8909 [root@svr7 ~]# setenforce 1 //开启强制模式 [root@svr7 ~]# systemctl restart httpd //起服务失败 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：
[root@svr7 ~]# grep 8909 /var/log/messages 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 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 .. ..使用完毕记得删除测试配置文件：
[root@svr7 ~]# rm -rf /etc/httpd/conf.d/8909.conf [root@svr7 ~]# systemctl restart httpd2）查看启动识别的鼠标设备信息
[root@svr7 ~]# dmesg | grep -i mouse [ 1.020385] mousedev: PS/2 mouse device common for all mice [ 1.249422] input: ImPS/2 Generic Wheel Mouse as /devices/platform/i8042/serio1/input/input2 [ 2.279665] usb 2-1: Product: VMware Virtual USB Mouse [ 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 [ 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/input03）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：
[root@svr7 ~]# last -2 zhsan pts/2 192.168.4.207 Fri Jan 6 18:00 - 18:00 (00:00) root pts/2 192.168.4.110 Fri Jan 6 17:26 - 17:59 (00:33) wtmp begins Thu Aug 4 00:10:16 2016查看失败登录的事件消息：
[root@svr7 ~]# lastb -2 anonymou ssh:notty 192.168.4.207 Fri Jan 6 18:00 - 18:00 (00:00) anonymou ssh:notty 192.168.4.207 Fri Jan 6 18:00 - 18:00 (00:00) btmp begins Fri Jan 6 18:00:34 20171）列出最近10条重要程度在ERR及以上的日志消息
[root@svr7 ~]# journalctl -p err -n 10 -- Logs begin at Thu 2017-01-05 15:50:08 CST, end at Fri 2017-01-06 18:01:01 CST. -- 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 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 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 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 Jan 06 17:53:48 svr7 setroubleshoot[33743]: Plugin Exception restorecon_source 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 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. Jan 06 17:53:54 svr7 systemd[1]: Failed to start The Apache HTTP Server. .. .. lines 1-11/11 (END)2）列出所有与服务httpd相关的消息
[root@svr7 ~]# journalctl -u httpd -- Logs begin at Thu 2017-01-05 15:50:08 CST, end at Fri 2017-01-06 18:01:01 CST. -- Jan 06 14:57:16 svr7 systemd[1]: Starting The Apache HTTP Server... Jan 06 14:57:16 svr7 httpd[23812]: AH00557: httpd: apr_sockaddr_info_get() failed for svr7 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 Jan 06 14:57:16 svr7 systemd[1]: Started The Apache HTTP Server. Jan 06 17:53:44 svr7 systemd[1]: Stopping The Apache HTTP Server... Jan 06 17:53:46 svr7 systemd[1]: Starting The Apache HTTP Server... Jan 06 17:53:46 svr7 httpd[33741]: AH00557: httpd: apr_sockaddr_info_get() failed for svr7 .. ..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：
[root@svr7 ~]# journalctl --since "2017-01-06 14:11" --until "2017-01-06 18:11" -- Logs begin at Thu 2017-01-05 15:50:08 CST, end at Fri 2017-01-06 18:10:01 CST. -- Jan 06 14:20:01 svr7 systemd[1]: Started Session 160 of user root. Jan 06 14:20:01 svr7 CROND[22869]: (root) CMD (/usr/lib64/sa/sa1 1 1) Jan 06 14:20:01 svr7 systemd[1]: Starting Session 160 of user root. Jan 06 14:30:01 svr7 systemd[1]: Started Session 161 of user root. Jan 06 14:30:01 svr7 CROND[23028]: (root) CMD (/usr/lib64/sa/sa1 1 1) Jan 06 14:31:39 svr7 systemd[1]: Starting Session 162 of user root. Jan 06 14:32:17 svr7 sshd[23046]: pam_unix(sshd:session): session closed for user root Jan 06 14:31:39 svr7 systemd[1]: Started Session 162 of user root. Jan 06 14:31:39 svr7 sshd[23046]: pam_unix(sshd:session): session opened for user root by (uid=0) Jan 06 14:31:39 svr7 systemd-logind[985]: New session 162 of user root. .. .
