You might be disappointed in this report if you're trying to answer the question "How much RAM is installed on this system?" This is the same system shown in the example above that was described as having 6GB of RAM.
With the -t option, free shows the same values as it does with no options (don't confuse -t with terabytes!) but by adding a total line at the bottom of its output. With the -g option, free reports the values in gigabytes. Total used free shared buff/cache available It gives you an easy-to-understand report on memory. $ expr 1024 \* 1024 \* 1024 \* 1024 \* 128 + 4096Īnother and more human-friendly command for examining memory is the free command.
Calculations of what 128 terabytes and that number, plus 4K would look like are fairly easy to make on the command line: $ expr 1024 \* 1024 \* 1024 \* 1024 \* 128 This number would suggest that the virtual memory on these systems is 128 terabytes! That number seems to represent instead how much memory a 64-bit systems might be capable of addressing - not how much is available on the system. r- 1 root root 140737477881856 Feb 5 13:00 /proc/kcoreĮxplanations that claim the size of this file represents the amount of available virtual memory (maybe plus 4K) don't hold much weight. The first of these two systems has 4 GB of memory installed the second has 6 GB. Interestingly, the two systems queried below do not have the same amount of memory installed, yet the size of /proc/kcore is the same on both. Instead, it is a virtual file like all of the files in /proc. This file looks like a normal (though extremely large) file, but it does not occupy disk space at all. One file that plays a role in memory management is /proc/kcore. Swap expands memory by providing disk space that can be used to house inactive pages that are moved to disk when physical memory fills up.
Some Linux commands provide information on both. Swap may include partitions set aside for this usage or files that are created to add to the available swap space when creating a new partition may not be practical. The latter includes disk space configured to be used as swap. Physical memory and virtual memory are not the same. In this post, we'll look at some of the more useful tools for checking on memory and its usage.īefore we get into the details, however, let's review a few basics. Some commands provide an overwhelming amount of detail, while others provide succinct, though not necessarily easy-to-digest, answers. There are numerous ways to get information on the memory installed on Linux systems and view how much of that memory is being used.
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