You can use the following commands to find out actual RAM size under Linux operating systems.
/proc/meminfo file
Type the following command to view total installed ram and used ram, enter:$ less /proc/meminfoOR
$ cat /proc/meminfoSample outputs:
MemTotal: 8177444 kB
MemFree: 1528304 kB
Buffers: 353152 kB
Cached: 2301132 kB
SwapCached: 0 kB
Active: 5250532 kB
Inactive: 983832 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 8177444 kB
LowFree: 1528304 kB
SwapTotal: 1052248 kB
SwapFree: 1052248 kB
Dirty: 1796 kB
Writeback: 0 kB
AnonPages: 3579784 kB
Mapped: 106548 kB
Slab: 295500 kB
PageTables: 82956 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
CommitLimit: 5140968 kB
Committed_AS: 4959796 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 263900 kB
VmallocChunk: 34359473347 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
Hugepagesize: 2048 kB
free Command
The free command displays the total amount of free and used physical and swap memory in the system, as well as the buffers used by the kernel:$ free -mOR
$ free -gSample outputs:
total used free shared buffers cached
Mem: 7985 6466 1519 0 344 2249
-/+ buffers/cache: 3871 4114
Swap: 1027 0 1027
Options
From the man page:The -b switch displays the amount of memory in bytes; the -k switch (set by default) displays it in kilobytes; the -m switch displays it in megabytes.
The -t switch displays a line containing the totals.
The -o switch disables the display of a "buffer adjusted" line. If the -o option is not specified, free subtracts buffer memory from the used memory and adds it to the free memory reported.
The -s switch activates continuous polling delay seconds apart. You may actually specify any floating point number for delay, usleep(3) is used for microsecond resolution delay times.
vmstat command
The vmstat command can display memory statistics including additional information about processes, paging, block IO, traps, and cpu activity. Type the following command:$ vmstat -sSample outputs:
8177444 total memory
6655064 used memory
5251360 active memory
989748 inactive memory
1522380 free memory
353316 buffer memory
2308588 swap cache
1052248 total swap
0 used swap
1052248 free swap
38412570 non-nice user cpu ticks
100117 nice user cpu ticks
5153239 system cpu ticks
271927635 idle cpu ticks
45717 IO-wait cpu ticks
63003 IRQ cpu ticks
564561 softirq cpu ticks
0 stolen cpu ticks
1846153 pages paged in
158053429 pages paged out
0 pages swapped in
0 pages swapped out
1226003322 interrupts
740976858 CPU context switches
1295805340 boot time
659452 forks
top Command
The top command provides a dynamic real-time view of a running system including a quick summary information about RAM, CPU as well as a list of tasks currently being managed by the Linux kernel. Type the following command:$ topSample outputs:
Fig.01: Display Linux RAM Size with the top commad
GUI System Information Tool
The System Monitor Gnome application enables you to display basic system information and monitor system processes, usage of system resources, and file systems. You can start System Monitor in the following ways:Click on System menu > Choose Administration > System Monitor
Or type the following command:
$ gnome-system-monitorSample outputs:
Fig.02: Linux view installed memory with the System Monitor application
dmidecode Command
The dmidecode command is used for dumping a computer's DMI (some say SMBIOS) table contents in a human-readable format. This table contains a description of the system's hardware components, as well as other useful pieces of information such as serial numbers and BIOS revision. Thanks to this table, you can retrieve this information without having to probe for the actual hardware. To see complete information about memory, enter:$ sudo dmidecode --type memorySample outputs:
# dmidecode 2.9
SMBIOS 2.6 present.
Handle 0x1000, DMI type 16, 15 bytes
Physical Memory Array
Location: System Board Or Motherboard
Use: System Memory
Error Correction Type: None
Maximum Capacity: 16 GB
Error Information Handle: Not Provided
Number Of Devices: 4
Handle 0x1100, DMI type 17, 28 bytes
Memory Device
Array Handle: 0x1000
Error Information Handle: Not Provided
Total Width: 64 bits
Data Width: 64 bits
Size: 4096 MB
Form Factor: DIMM
Set: None
Locator: DIMM_A
Bank Locator: Not Specified
Type:
Type Detail: Synchronous
Speed: 1333 MHz (0.8 ns)
Manufacturer: 80CE000080CE
Serial Number: 45AAFB60
Asset Tag: 01101800
Part Number: M471B5273CH0-CH9
Handle 0x1101, DMI type 17, 28 bytes
Memory Device
Array Handle: 0x1000
Error Information Handle: Not Provided
Total Width: 64 bits
Data Width: 64 bits
Size: 4096 MB
Form Factor: DIMM
Set: None
Locator: DIMM_B
Bank Locator: Not Specified
Type:
Type Detail: Synchronous
Speed: 1333 MHz (0.8 ns)
Manufacturer: 80CE000080CE
Serial Number: 45AAFDAD
Asset Tag: 01101800
Part Number: M471B5273CH0-CH9
Handle 0x1102, DMI type 17, 28 bytes
Memory Device
Array Handle: 0x1000
Error Information Handle: Not Provided
Total Width: 64 bits
Data Width: 64 bits
Size: No Module Installed
Form Factor: DIMM
Set: None
Locator: DIMM_C
Bank Locator: Not Specified
Type:
Type Detail: Synchronous
Speed: Unknown
Manufacturer:
Serial Number:
Asset Tag:
Part Number:
Handle 0x1103, DMI type 17, 28 bytes
Memory Device
Array Handle: 0x1000
Error Information Handle: Not Provided
Total Width: 64 bits
Data Width: 64 bits
Size: No Module Installed
Form Factor: DIMM
Set: None
Locator: DIMM_D
Bank Locator: Not Specified
Type:
Type Detail: Synchronous
Speed: Unknown
Manufacturer:
Serial Number:
Asset Tag:
Part Number:
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