mem(4)

💖 mem — bestie, we're going straight into the machine 💖

okay so this is mem(4) from the Kernel Interfaces Manual, and it's the one where you literally vibe-check the computer's actual memory. raw. unfiltered. main character energy on the lowest level possible.

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✨ NAME ✨

mem, kmem, port</p> — system memory, kernel memory and system ports. that's the trio. the whole squad. 🫶

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🌸 DESCRIPTION 🌸

/dev/mem is a character device file that is an image of the main memory of the computer. like, the whole memory. the actual memory. no cap. 🔥

it may be used, for example, to examine (and even patch) the system. yes, patch. we love a file that lets you poke the machine directly.

Byte addresses in /dev/mem are interpreted as physical memory addresses. so when you seek somewhere, you're seeking in real, actual, physical space. References to nonexistent locations cause errors to be returned — the kernel is not gonna pretend it knows what you're talking about, bestie. it'll just error out. 💀

heads up, babes: examining and patching is likely to lead to unexpected results when read-only or write-only bits are present. it's giving chaos. stay aware.

Since Linux 2.6.26, and depending on the architecture, the CONFIG_STRICT_DEVMEM kernel configuration option limits the areas which can be accessed through this file. For example: on x86, RAM access is not allowed, but accessing memory-mapped PCI regions is. so it's a selective-access situation. an exclusive club. 🎀

It is typically created by:

mknod -m 660 /dev/mem c 1 1
chown root:kmem /dev/mem

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The file /dev/kmem is the same as /dev/mem, except that the kernel virtual memory rather than physical memory is accessed. same vibe, different address space. 🦋

Since Linux 2.6.26, this file is available only if the CONFIG_DEVKMEM kernel configuration option is enabled. no config option, no /dev/kmem. that's the rule.

It is typically created by:

mknod -m 640 /dev/kmem c 1 2
chown root:kmem /dev/kmem

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/dev/port is similar to /dev/mem, but the I/O ports are accessed. different door, same energy. ✨

It is typically created by:

mknod -m 660 /dev/port c 1 4
chown root:kmem /dev/port

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🎀 FILES 🎀

• /dev/mem
• /dev/kmem
• /dev/port

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👑 SEE ALSO 👑

• chown(1)
• mknod(1)
• ioperm(2)

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and that's the tea, bestie — this page came to you straight out of Linux man-pages 6.20, dated 2025-05-17, and it's mem(4) so you know where to find it again. go forth and respect the memory. periodt. 💅💖🌈