Summary of essential linux commands for fire fighting (1) ------ query problems

Summary of essential linux commands for fire fighting (I) ------ some commands are essential when you check online problems. it is necessary to summarize some common commands (such commands and related parameters are quite a lot, only summarize the commonly used ones). Generally, you can find problems by system parameters, performance parameters, processes ,... summary of essential linux commands for fire fighting (I) ------ some commands are essential when you check online problems. it is necessary to summarize some common commands (such commands and related parameters are quite a lot, you can only summarize the commonly used ones). Generally, you can find problems in the following categories: System parameters, performance parameters, processes, memory, network, storage, memory, and jvm: system parameters cat/proc/cpuinfo cpu-related parameters cat/proc/meminfo memory-related parameters cat/proc/loadavg performance parameters 1) top M: Sort by memory usage P: sort by CPU usage 1: Display the usage of each CPU k: kill process o: more sorting rules press enter: refresh data 2) ulimitulimit-: displays the user's system restriction parameter ulimit-Hn : Change the maximum number of Hard open files ulimit-Sn : Change the maximum number of Soft open files 3) vmstatvmstat 5-S m: Refresh vmstat data (unit: m) process 1) ps aux: show all user process details ps-ef: show all user process details another style if not all display can be widened via-w, such as ps aux-www network 1) netstat-na: show all network connections netstat-nap: show all network connections with process-related information netstat-nat: show all tcp network connections netstat-ln: display network connection storage in all monitoring statuses 1) df-h: hard disk storage Overall situation 2) du -- max-depth = 1-h <路径> : Specify the size of all folders in the path (recursive layer) 3) du-sh <路径> : Specify the directory size memory free-m it is worth noting that: Idle memory = free + buffers + cached = total-usedJVM 1) jstatjstat-gccapacity : Remaining jstat-gcutil status in each JVM region : Jstat-gccause : The reason for jstat-gcutil base addition of gc can also specify the update frequency, such as-h5 1 s: update every second, and add the header to display 2 at every five) jps currently running java process 3) jmap-dump: format = B, file = jmap. log : Generate heap dump file jmap-heap : Displays the overall situation of jvm heap. jmap-histo: live : Display memory usage of class instances 4) jstack-l : Display thread blocking/deadlock