文件跟踪查看/实时查看添加到⽂件中的内容/linux日志查看

追踪更新中的文件

• tail -f -n <lineNumbers> <logFile> | nl

查看某个文件的末尾N行,并带上源文件中的行号

• nl <logFile> tail -n <lineNumbers>

查看linux内核日志

相关参考

• What are Linux Logs? Code Examples, Tutorials & More (stackify.com)

  • A Definition of Linux Logs
  • How to View Linux Logs
  • Most Important Linux Logs
  • Critical, Must Monitor Logs
  • Sample Output
  • Additional Resources and Tutorials on Linux Logs

• Classic SysAdmin: Viewing Linux Logs from the Command Line

  • /var/log
  • Viewing logs with less
  • Viewing logs with dmesg
  • Viewing logs with tail

• How to View System Log Files in Linux (linuxhint.com)

• Analyzing and Managing System Log Files | System Analysis and Tuning Guide | SUSE Linux Enterprise Server 12 SP4

• How to View & Read Linux Log Files
  • What are Linux Log Files?
  • How to View Linux Logs
  • Important Linux System Logs
    • System Logs
    • System Logging Daemon
    • Application Logs
    • Non-Human-Readable Logs
  • Supplemental GUIs for Viewing Linux Log Files
  • How to Configure Log Files on Ubuntu and CentOS
  • Execute Log Rotation

日志查看示例

查看开机日志

ubuntu

• sudo tail -f /var/log/boot.log

# cxxu @ cxxuAli in /var/log [19:00:25] C:1
$ sudo tail -f boot.log
[sudo] password for cxxu:
[  OK  ] Started Permit User Sessions.
[  OK  ] Started ECS enable networking multiqueue.
[  OK  ] Started resolvconf-pull-resolved.service.
[  OK  ] Started OpenBSD Secure Shell server.
[  OK  ] Started chrony, an NTP client/server.
[  OK  ] Started LSB: starts the nginx web server.
[  OK  ] Started LSB: Record successful boot for GRUB.
[  OK  ] Started Accounts Service.
         Starting Terminate Plymouth Boot Screen...
         Starting Hold until boot process finishes up...

授权日志

# cxxu @ cxxuAli in /var/log [19:02:53]
$ sudo tail /var/log/auth.log
Sep 29 18:59:37 cxxuAli sshd[24798]: pam_unix(sshd:session): session opened for user cxxu by (uid=0)
Sep 29 18:59:37 cxxuAli systemd-logind[584]: New session 23215 of user cxxu.
Sep 29 19:00:35 cxxuAli sudo:     cxxu : TTY=pts/0 ; PWD=/var/log ; USER=root ; COMMAND=/usr/bin/tail -f boot.log
Sep 29 19:00:35 cxxuAli sudo: pam_unix(sudo:session): session opened for user root by cxxu(uid=0)
Sep 29 19:00:45 cxxuAli sudo: pam_unix(sudo:session): session closed for user root
Sep 29 19:02:53 cxxuAli sudo:     cxxu : TTY=pts/0 ; PWD=/var/log ; USER=root ; COMMAND=/bin/cat /var/log/auth.log
Sep 29 19:02:53 cxxuAli sudo: pam_unix(sudo:session): session opened for user root by cxxu(uid=0)
Sep 29 19:02:53 cxxuAli sudo: pam_unix(sudo:session): session closed for user root
Sep 29 19:03:10 cxxuAli sudo:     cxxu : TTY=pts/0 ; PWD=/var/log ; USER=root ; COMMAND=/usr/bin/tail /var/log/auth.log
Sep 29 19:03:10 cxxuAli sudo: pam_unix(sudo:session): session opened for user root by cxxu(uid=0)

Conclusion

• Examining various log files can help in debugging system freeze and crash issues, especially when new and unsupported hardware is present in the PC.
• These log files are also useful for finding out security breaches or security loopholes if there are any.
• If you are getting unexpected behavior from software installed on your system or frequent reboots and crashes, the first thing you should do is to examine various system log files.