Linux - Analyzing and Troubleshooting System Faults

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Table of contents

log function

Classification of log files

log message level

User log analysis tools:

command summary

log function

1>It is used to record various events that occur in the system and program operation
2>By reading the log, it is helpful for diagnosing and solving system failures

Classification of log files

1 Kernel and system logs
Unified management by the system service syslog, the log format is basically similar
2 user logs
Record system user login and logout information
3 program log
Log files independently managed by various applications, the record format is not uniform

log message level

0 EMERG (emergency): a condition that would render the host system unavailable
1 ALERT: A problem that requires immediate action
2 CRIT (serious): more serious situation
3 ERR (error): An error occurred while running
4 WARNING: Events that may affect system functionality
5 NOTICE (Note): Will not affect the system but worth noting
6 INFO (information): general information
7 DEBUG (debugging): program or system debugging information, etc.

User log analysis tools:

1> Query the status of the currently logged-in user: users, who, w
2> Query the history of user login: last (success), lastb (failure)

Save the user login, logout system and other related information
/var/log/lastlog: recent user login events
/var/log/wtmp: user login, logout and system startup and shutdown events
/var/run/utmp: details of each user currently logged in
/var/log/secure: Security events related to user authentication
Analysis tools users, who, w, last, lastb

command summary

Log default save location: /var/log directory

forget ROOT password, use the command
chroot /mnt/sysimage
passwd root

View the usage of i nodes in the file system
df -i /data

The command to detect disk bad sectors:
badblocks -sv /dev/sdb
("-v": display details "-s": display progress information)