Free RAMであれば、以下のコマンドで確認できます。

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service show sysinfo

System Information:

Free RAM: 50.3% (416696 of 828332) Min: 10.0%
File Descriptors: free: 81634 used: 1056 max: 25500
CPU load averages: 1 min: 0.5% 5 min: 0.2% 15 min: 0.2%

Kernel Buffers:
Size: 32 64 128 256 512 1k 2k 4k 8k 16k 32k 64k 128k
Usage: 0 0 0 0 0 0 0 0 0 0 0 0 0
Limit: 32768 32678 4096 4096 8192 8192 16384 16384 1024 512 256 64 64

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