There are a few commands that can help us to check the memory usage in linux server. The usage including free memory, used physical memory, swap memory and also buffers used by the kernel.
1. Type top command at ssh login or terminal.
[root@server ~]# top
Sample outputs:
top - 23:35:48 up 1:36, 1 user, load average: 0.00, 0.01, 0.02
Tasks: 67 total, 1 running, 66 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.4%us, 1.8%sy, 0.1%ni, 95.6%id, 2.1%wa, 0.1%hi, 0.0%si, 0.0%st
Mem: 604324k total, 329952k used, 274372k free, 65428k buffers
Swap: 1052248k total, 0k used, 1052248k free, 208324k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1 root 15 0 2156 640 548 S 0.0 0.1 0:01.03 init
2 root RT -5 0 0 0 S 0.0 0.0 0:00.00 migration/0
3 root 34 19 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/0
4 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/0
5 root 10 -5 0 0 0 S 0.0 0.0 0:00.00 events/0
6 root 10 -5 0 0 0 S 0.0 0.0 0:00.00 khelper
7 root 11 -5 0 0 0 S 0.0 0.0 0:00.00 kthread
10 root 10 -5 0 0 0 S 0.0 0.0 0:00.01 kblockd/0
11 root 20 -5 0 0 0 S 0.0 0.0 0:00.00 kacpid
170 root 15 -5 0 0 0 S 0.0 0.0 0:00.00 cqueue/0
173 root 15 -5 0 0 0 S 0.0 0.0 0:00.00 khubd
175 root 10 -5 0 0 0 S 0.0 0.0 0:00.00 kseriod
240 root 15 0 0 0 0 S 0.0 0.0 0:00.00 khungtaskd
241 root 20 0 0 0 0 S 0.0 0.0 0:00.00 pdflush
242 root 15 0 0 0 0 S 0.0 0.0 0:00.20 pdflush
243 root 15 -5 0 0 0 S 0.0 0.0 0:00.00 kswapd0
244 root 15 -5 0 0 0 S 0.0 0.0 0:00.00 aio/0
2. Type vmstat command at ssh login or terminal
[root@server ~]# vmstat
Sample outputs:
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------ r b swpd free buff cache si so bi bo in cs us sy id wa st 0 0 0 273256 65688 208884 0 0 79 39 1039 84 0 2 96 2 0
3. Display free memory in bytes, KB, MB, or GB
usage: free [-b|-k|-m|-g] [-l] [-o] [-t] [-s delay] [-c count] [-V]
-b,-k,-m,-g show output in bytes, KB, MB, or GB
-l show detailed low and high memory statistics
-o use old format (no -/+buffers/cache line)
-t display total for RAM + swap
-s update every [delay] seconds
-c update [count] times
-V display version information and exit
Type below command if you want to displays a line containing the totals memory in MB:
[root@server ~]# free -m -t
Sample outputs:
total used free shared buffers cached Mem: 590 323 266 0 64 204 -/+ buffers/cache: 54 535 Swap: 1027 0 1027 Total: 1617 323 1294
4. Cat the /proc/meminfo to get the memory usage information as below:
[root@server ~]# cat /proc/meminfo
Sample outputs:
MemTotal: 604324 kB MemFree: 272512 kB Buffers: 66040 kB Cached: 209256 kB SwapCached: 0 kB Active: 61864 kB Inactive: 222596 kB HighTotal: 0 kB HighFree: 0 kB LowTotal: 604324 kB LowFree: 272512 kB SwapTotal: 1052248 kB SwapFree: 1052248 kB Dirty: 1032 kB Writeback: 0 kB AnonPages: 9172 kB Mapped: 6468 kB Slab: 39896 kB PageTables: 972 kB NFS_Unstable: 0 kB Bounce: 0 kB CommitLimit: 1354408 kB Committed_AS: 76248 kB VmallocTotal: 417784 kB VmallocUsed: 4052 kB VmallocChunk: 413304 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 Hugepagesize: 4096 kB