free displays the total amount of free and used physical and swap memory in the system, as well as the buffers and caches used by the kernel. The information is gathered by parsing /proc/meminfo.
The displayed columns are:
total Total usable memory (MemTotal and SwapTotal in /proc/meminfo). This includes the physical and swap memory minus a few reserved bits and kernel binary code.
used Used or unavailable memory (calculated as total – available)
free Unused memory (MemFree and SwapFree in /proc/meminfo)
shared Memory used (mostly) by tmpfs (Shmem in /proc/meminfo)
buffers Memory used by kernel buffers (Buffers in /proc/meminfo)
cache Memory used by the page cache and slabs (Cached and SReclaimable in /proc/meminfo)
buff/cache Sum of buffers and cache
available Estimation of how much memory is available for starting new applications, without swapping. Unlike the data provided by the cache or free fields, this field takes into account page cache and also that not all reclaimable memory slabs will be reclaimed due to items being in use (MemAvailable in /proc/meminfo, available on kernels 3.14, emulated on kernels 2.6.27+, otherwise the same as free)
| Alternatives to free | |
|---|---|
| frei | Modern replacement for the free command |
| vmstat | Reports info about processes, memory, paging, block IO, traps, disks and cpu activity |
| musage | Command line memory usage information tool |
| bfree | Human-friendly view of Linux memory and swap |
All the CLI tools in this series.
| Alternatives to CLI tools |
|---|
| age // awk // bc // cal // cat // cd // chmod // cksum // cloc // cmp // compress // cp // cron // curl // cut // date // dd // df // diff // dig // du // fdisk // file // find // free // ftp // grep // gzip // hexdump // history // jq // kill // less // locate // ls // lsof // make // man // more // mv / ping // ps // psql // rename // rm // sed // split // ssh // stow // strings // sudo // sysctl // tail // talk // tar // telnet // time // top // touch // traceroute // tree // uname // uniq // uptime // vi // watch // Wget // who // whois // xargs |
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