Here are 3 simple ways to check your systems current RAM usage, when working via command line.
The free command has multiple options. Free on its own will provide you the ram usage in bytes. This is probably useless to most so adding -m after it will give you the value in megabytes.
free -m
The output should be something like this
total used free shared buffers cached
total used free shared buffers cached Mem: 4096 712 3383 131 0 307 -/+ buffers/cache: 405 3690 Swap: 128 0 128
An alternative is to use top. This will give you the specific applications that are using the memory along with CPU usage. The best thing about this command is it’s in real time. The data is very much like that displayed in task manager for Windows.
top
This should output something like this
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1 root 20 0 19364 436 132 S 0.0 0.0 0:01.11 init 2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd/69576 3 root 20 0 0 0 0 S 0.0 0.0 0:00.00 khelper/69576 4 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rpciod/69576/0 5 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rpciod/69576/1 6 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rpciod/69576/2 7 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rpciod/69576/3 8 root 20 0 0 0 0 S 0.0 0.0 0:00.00 nfsiod/69576 127 root 16 -4 10652 280 0 S 0.0 0.0 0:00.01 udevd 499 root 20 0 179m 2256 324 S 0.0 0.1 0:10.23 rsyslogd 545 named 20 0 307m 26m 1720 S 0.0 0.7 1:24.78 named 563 root 20 0 4580 148 60 S 0.0 0.0 0:00.06 mdadm 572 dbus 20 0 21436 236 4 S 0.0 0.0 0:00.00 dbus-daemon 610 root 20 0 66220 900 192 S 0.0 0.0 0:07.61 sshd 621 root 20 0 52112 628 88 S 0.0 0.0 0:00.28 vsftpd 657 root 20 0 105m 304 4 S 0.0 0.0 0:00.05 mysqld_safe 864 mysql 20 0 1727m 170m 3940 S 0.0 4.2 49:40.23 mysqld
vmstat is another simple way to check RAM usage. This isn’t quite as useful if you want to quicky check. It will display most of what the free command displays along with a few extra details.
vmstat -s
Output
4194304 total memory 728952 used memory 296176 active memory 383972 inactive memory 3465352 free memory 0 buffer memory 314504 swap cache 131072 total swap 0 used swap 131072 free swap 887837 non-nice user cpu ticks 1429 nice user cpu ticks 199846 system cpu ticks 182661931 idle cpu ticks 134832 IO-wait cpu ticks 0 IRQ cpu ticks 0 softirq cpu ticks 0 stolen cpu ticks 13589860 pages paged in 5739148 pages paged out 0 pages swapped in 0 pages swapped out 0 interrupts 46730701 CPU context switches 1423896862 boot time 105029 forks
While on the subject of RAM the following commands will give you the technical information about the RAM that is installed on the system you are working on. dmidecode will get you the max capacity, number of devices and some other basic information.
dmidecode -t 16
dmidecode -t 17