Last time we talked about how /proc has directories for each process but that there were also some files in that directory.  This time we’ll talk about a couple of those files.  /proc and its files have lots of information about the running of your system.

Let’s start with meminfo.  That’s a weird name, right?  Well, surprise, surprise, it has something to do with memory.  It has the current state of the memory on your system.

MemTotal:       32953488 kB
MemFree:        12891648 kB
Buffers:           56460 kB
Cached:          7736136 kB
SwapCached:       720288 kB
Active:         12263732 kB
Inactive:        5540668 kB
Active(anon):    9316432 kB
Inactive(anon):  3067828 kB
Active(file):    2947300 kB
Inactive(file):  2472840 kB
Unevictable:       26100 kB
Mlocked:           15880 kB
SwapTotal:       3117180 kB
SwapFree:        1736868 kB
Dirty:              1820 kB
Writeback:             0 kB
AnonPages:       9560840 kB
Mapped:          2414060 kB
Shmem:           2369068 kB
Slab:             768816 kB
SReclaimable:     521000 kB
SUnreclaim:       247816 kB
KernelStack:       18416 kB
PageTables:       365784 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:    19593924 kB
Committed_AS:   27252100 kB
VmallocTotal:   34359738367 kB
VmallocUsed:      276548 kB
VmallocChunk:   34359361512 kB
AnonHugePages:    491520 kB
DirectMap4k:        7488 kB
DirectMap2M:     4179968 kB
DirectMap1G:    29360128 kB

That’s a lot of information and we don’t really care what it all means.  The first two lines are the interesting part, they tell us the total memory on the system (in kilobytes). This system has 32 Gigabytes of memory installed on it and 39% of it is being used.  (I figured that out by dividing the amount of memory being used by the memory on the system).

Another file is the devices file.  That’s a list of devices on the system.  Remember, /dev/  has a list of all possible devices, the devices file in /proc has a list of all the devices on the system.  I can cat that one and see:

Character devices:
  1 mem
  2 pty
  3 ttyp
  4 /dev/vc/0
  4 tty
  5 /dev/tty
  5 /dev/console
  5 /dev/ptmx
  7 vcs
 10 misc
 13 input
108 ppp
128 ptm
136 pts
229 hvc
254 uio

Block devices:
  1 ramdisk
259 blkext
  7 loop
  9 md
 43 nbd
147 drbd
202 xvd
253 device-mapper
254 mdp

So the question now is, what’s a block device and what’s a character device?  Tune in next time for more information… Same bat time, same bat station!