===/proc===
stat (cpu,disk,swap)
  cpu user nice system idle iowait irq softirq (in 1/100ths of a second)
partitions partition sizes in 1k blocks
diskstats /usr/src/linux/Documentation/iostats.txt
net/tcp tcp open connection list
meminfo
  used = total - free - buffers - cached - slab
  swaptotal, swapfree
vmstat
  pswpin, pswpout
mounts
acpi/battery/BAT1/{state|info}
acpi/ac_adapter/ACAD/state
uptime
  total idle
acpi/thermal_zone/THRM/temperature

===commands===
amixer get PCM