Shulou(Shulou.com)06/03 Report--

1. System monitoring 1. Free command

The free command displays the physical free and used memory in the system, as well as swapped memory, as well as the buffers and caches used by the kernel

Syntax: free [param]

Param can be:

-b: displays memory usage in Byte

-k: displays memory usage in KB

-m: displays memory usage in MB

-o: do not show buffer adjustment column

-s: continuously observe memory usage

-t: displays the memory sum column

-V: displays version information.

Mem: represents physical memory statistics

Total: represents the total physical memory (total=used+free)

Used: indicates the amount that the system allocates to cache usage (the cache here includes buffer and cache)

Free: represents the total number of unallocated physical memory

Shared: indicates shared memory

Buffers: the number of buffers allocated by the system but not used.

Cached: the number of cache allocated by the system but not used.

-/ + buffers/cache: indicates the cache statistics of physical memory

(- buffers/cache) memory: (refers to the used-buffers-cached in the first part of the Mem line)

(+ buffers/cache) memory: (refers to free + buffers + cached in the first part of the Mem line)

(- buffers/cache) indicates the number of memory actually used, and (+ buffers/cache) indicates the number of memory that is really unused

Swap: indicates the use of swapped partitions on the hard disk

2. Ulimit command

Ulimit is used to display information about system resource limits

Syntax: ulimit [param]

The param parameter can be:

-a displays the current resource limit settings.

-c sets the maximum value of the core file in blocks.

-d the maximum value of the program data section in KB.

-f shell can create the largest file, in chunks.

-H sets hard limits on resources, that is, those set by administrators.

-m specifies the upper limit of available memory in KB.

-n specifies the maximum number of files that can be opened at a time.

-p specifies the size of the pipe buffer in 512 bytes.

-s specifies the upper limit of the stack in KB.

-S sets flexible limits for resources.

-t specifies the upper limit of CPU usage time (in seconds).

-u the maximum number of programs that users can open.

-v specifies the upper limit of virtual memory available in KB

3. Top command

The top command can view the overall operation of the system in real time and dynamically. It is a practical tool that integrates multi-party information to monitor the performance and operation information of the system.

Syntax: top [param]

The param is:

-b: operate in batch mode

-c: displays the complete governance command

-d: screen refresh interval

-I: ignore the failure process

-s: secret mode

-S: cumulative mode

-u [user name]: specify a user name

-p [process number]: specify the process

-n [times]: the number of times the loop is displayed.

4. Df command

Df-h to view disk usage

Df-I view inode usage

5. Ps command

The ps command is used to view process statistics

Common parameters:

A: displays all the process information under the current terminal, including the processes of other users.

U: use a user-based format to output process information.

X: displays the progress of the current user under all terminals.

-e: displays all process information in the system.

-l: displays process information in long format.

-f: displays process information in full (full) format.

You can use it with the grep command, or you can use it alone

Situations where the ps command is used alone

Ps-elf tomcat

# filter with pipeline operation and grep command to query the information of a process

Ps-elf | grep tomcat

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