freeramdisk

Free loadlin ramdisk memory

$ sudo freeramdisk

The `freeramdisk` command was typically invoked with the path to the RAM disk device.
Syntax (historical/illustrative):
freeramdisk /dev/ramN

/dev/ramN
    The device node corresponding to the RAM disk (e.g., /dev/ram0, /dev/ram1) whose memory pages were to be freed. No standard options were typically associated with this command.

The `freeramdisk` command is an obsolete utility historically used in early Linux kernel versions (primarily 2.0.x and 2.2.x) to explicitly mark memory pages associated with a kernel RAM disk device (e.g., /dev/ram0) as free, allowing them to be reused by the system. In older Linux kernels, RAM disks were typically managed by the `ramdisk` kernel module, and their memory might not have been automatically released upon unmounting or system shutdown as efficiently as modern memory management. This command provided a way to reclaim that memory manually after a RAM disk was no longer needed. It was often employed in early boot scripts (e.g., in `initrd`) before transitioning to the root filesystem.

Modern Linux distributions no longer include or require `freeramdisk`. Its functionality has been superseded by more advanced and automatic memory management within the kernel, particularly through the use of `tmpfs` and `ramfs` filesystems, which automatically handle memory allocation and deallocation for in-memory storage, and the `brd` (block ramdisk) module for block-device-based RAM disks. Memory used by these modern in-memory filesystems or block devices is automatically freed when they are unmounted or removed.

This command is obsolete and not available in modern Linux distributions. Attempting to run `freeramdisk` on a contemporary system will result in a "command not found" error. Its functionality has been entirely absorbed and improved upon by the kernel's built-in memory management and modern in-memory filesystem types like `tmpfs` and `ramfs`. Users should use `tmpfs` for temporary filesystems residing in RAM, and memory will be automatically managed.

For creating and managing RAM-based storage in modern Linux, consider using `tmpfs` for file system-like storage in RAM, or the `brd` kernel module (block ramdisk) for block device-like storage. `tmpfs` is a virtual memory filesystem that stores its contents in virtual memory (RAM and swap). It is created using `mount -t tmpfs -o size=... tmpfs /mnt/ramdisk`. Memory is automatically freed upon unmount. `ramfs` is a simpler, older in-memory filesystem that doesn't support swapping, primarily used for very small, ephemeral data.

The `freeramdisk` utility was part of the early Linux toolset, particularly prominent during the 2.0.x to 2.2.x kernel series. It addressed a specific need for explicit memory reclamation from RAM disks when kernel memory management for these devices was less sophisticated. As the Linux kernel evolved, particularly with the introduction of virtual filesystems like `tmpfs` (which became standard around kernel 2.4) and enhancements to the block device layer, the need for a separate `freeramdisk` command diminished. Its functionality was integrated directly into the kernel's handling of RAM-based storage, leading to its deprecation and eventual removal from common Linux distributions.

tmpfs(5), mount(8), brd(4), ramfs