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Chapter 2. The

proc

File System

2.2.18.

/proc/mdstat

This file contains the current information for multiple disk, RAID configurations. If your system does

not contain such a configuration, then your

/proc/mdstat

file will look similar to this:

Personalities :

read_ahead not set

unused devices:

none

This file remains in the state above unless you create a software RAID or

md

device. In that case, you

can view

/proc/mdstat

to give you a picture of what is currently happening with your

mdX

RAID

devices.

The

/proc/mdstat

file below shows a system with its

md0

configured as a RAID 1 device. It is

currently re syncing the disks:

Personalities : [linear] [raid1]

read_ahead 1024 sectors

md0: active raid1 sda2[1] sdb2[0] 9940 blocks [2/2] [UU] resync=1% finish=12.3min

algorithm 2 [3/3] [UUU]

unused devices:

none

2.2.19.

/proc/meminfo

This is one of the more commonly used files in the

/proc/

directory, as it reports back plenty of

valuable information about the current RAM usage on the system. A system with 256MB of RAM

and 384MB of swap space will likely have a

/proc/meminfo

file similar to this one:

total:

used:

free:

shared: buffers:

cached:

Mem:

261709824 253407232

8302592

0 120745984 48689152

Swap: 402997248

8192 402989056

MemTotal:

255576 kB

MemFree:

8108 kB

MemShared:

0 kB

Buffers:

117916 kB

Cached:

47548 kB

Active:

135300 kB

Inact_dirty:

29276 kB

Inact_clean:

888 kB

Inact_target:

0 kB

HighTotal:

0 kB

HighFree:

0 kB

LowTotal:

255576 kB

LowFree:

8108 kB

SwapTotal:

393552 kB

SwapFree:

393544 kB

Much of the information here is used by the

free

,

top

, and

ps

commands. In fact, the output of the

free

command is even similar in appearance to the contents and structure of

/proc/meminfo

. But

by looking directly at

/proc/meminfo

, more details are revealed:

  Mem

  Displays the current state of physical RAM in the system, including a full breakdown of

total, used, free, shared, buffered, and cached memory utilization in bytes.

  Swap

  Displays the total, used, and free amounts of swap space, in bytes.

  MemTotal

  Total amount of physical RAM, in kilobytes.