Installation guide

32 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.