Anonymoususer852: vmlinuz actually also contains COFF. Also discuss about vmlinux versus vmlinuz.

2025-08-15T14:09:09Z

vmlinuz actually also contains COFF. Also discuss about vmlinux versus vmlinuz.

Anonymoususer852: Created page with "{{FormatInfo |name=vmlinuz |formattype=electronic |subcat=Executables |extensions={{noext}} |compression=lossless }} '''vmlinuz''' is a ELF..."

2025-08-15T11:23:00Z

Created page with "{{FormatInfo |name=vmlinuz |formattype=electronic |subcat=Executables |extensions={{noext}} |compression=lossless }} '''vmlinuz''' is a ELF..."

New page

{{FormatInfo
|name=vmlinuz
|formattype=electronic
|subcat=Executables
|extensions={{noext}}
|compression=lossless
}}

'''vmlinuz''' is a [[Executable and Linkable Format|ELF]] that contains a pre-compiled, compressed [[Linux]] kernel image, and is required to boot into a Linux environment. While the filename may vary across Linux distributions, e.g. <code>vmlinuz-6.15.9-201.fc42.x86_64</code><ref>[https://koji.fedoraproject.org/koji/rpminfo?rpmID=43854624 Information for RPM kernel-core-6.15.9-201.fc42.x86_64.rpm - Fedora buildsystem - koji.fedoraproject.org]</ref> or <code>vmlinuz-linux</code><ref>[https://bbs.archlinux.org/viewtopic.php?pid=2101137#p2101137 (SOLVED) What creates /boot/vmlinuz-linux ? - bbs.archlinux.org]</ref> the filename generally starts with <code>vmlinuz</code>.

This file is also commonly paired with [[initramfs]], residing in <code>/boot</code> directory, enables loading of extra kernel objects (<code>.ko</code>)<ref>[https://unix.stackexchange.com/a/424603 Is "update-initramfs -u" needed after adding or removing a module with "modprobe"? - Unix & Linux Stack Exchange]</ref> along with any other added data that is necessary to;
* <code>mount</code> the filesystem, for example provide OpenZFS on deployments that uses OpenZFS filesystem as its rootfs,<ref>[https://packages.debian.org/sid/zfs-initramfs Debian -- Details of package zfs-initramfs in sid - packages.debian.org]</ref>
* Early load files, such as AMD/Intel CPU microcodes,<ref>[https://docs.kernel.org/arch/x86/microcode.html 25. The Linux Microcode Loader - docs.kernel.org]</ref>
* Provide a rescue environment if in case there is an issue while trying to initialize <code>pivot_root</code>.<ref>[https://wiki.gentoo.org/wiki/Initramfs_-_make_your_own#Elements_of_the_Init_Script Elements of the Init Script section - Initramfs - make your own - Gentoo Wiki]</ref>

Without vmlinuz, the system may fail booting at the bootloader stage, typically instructing the user the stated file is not found.

== Discussion ==
There are no agreed amount of vmlinuz and initramfs to have inside any Linux installation. Fedora Linux retains a maximum of three, any older versions are replaced with newer versions when the system updates includes newer kernel in distro repository. Arch Linux, on the other hand defaults to one, which will automatically replace the contents as soon as linux package is located during system upgrade.

"vmlinu'''x'''" as opposed to "vmlinu'''z''', are considered to be uncompressed and unbootable variant of vmlinu'''z'''.<ref>[[wikipedia:Vmlinux#Etymology|Etymology section on Wikipedia]]</ref><ref>[https://stackoverflow.com/a/41813945 What is the use of vmlinux file generated when we compile linux kernel - StackOverflow]</ref><ref>[https://www.linfo.org/vmlinuz.html vmlinuz Definition - linfo.org]</ref> While [[Compression#Stream_compression_formats|stream compression]] typically used<ref>[https://raw.githubusercontent.com/torvalds/linux/master/scripts/extract-vmlinux extract-vmlinux (shell script) - Linus Torvalds' Linux (kernel) repository - GitHub]</ref> are either:
* [[gzip|gunzip or gzip]],
* [[bzip2]],
* [[LZ4]],
* [[lzop]],
* [[LZMA]],
* [[XZ]],
* [[Zstandard]]

== Identification ==
A x86 <code>vmlinuz</code> contains {{magic|48 64 72 53}} at offset 0x202, which in ASCII format is the string <code>HdrS</code>.<ref>[https://github.com/file/file/blob/master/magic/Magdir/linux#L145 linux (line 145) - file - GitHub]</ref>

== Software ==
* Generation:
** [https://www.gnu.org/software/make/ <code>make bzImage</code>]<ref>[https://www.linfo.org/vmlinuz.html vmlinuz Definition - linfo.org]</ref>
* Other:
** [[File command|<code>file</code>]] - Used to identify the type of file by its magic bytes
** [https://raw.githubusercontent.com/torvalds/linux/master/scripts/extract-vmlinux <code>extract-vmlinux</code>] - From Linus Torvald's Linux kernel repository. Used to extract vmlinuz
** [https://www.gnu.org/software/binutils/ GNU Binutils] → objdump - For examining the [[Executable and Linkable Format|ELF]]
** [https://www.gnu.org/software/binutils/ GNU Binutils] → readelf - For examining the [[Executable and Linkable Format|ELF]]

== Links ==
* [[wikipedia:vmlinux|vmlinux page on Wikipedia]]
* [https://trendoceans.com/how-to-extract-and-disassemble-vmlinuz-file/ How to extract and disassemble vmlinuz file - Trend Oceans]

== Referencs ==
<references/>

@@ Line 7: / Line 7: @@
 }}
-'''vmlinuz''' is a [[Executable and Linkable Format|ELF]] that contains a pre-compiled, compressed [[Linux]] kernel image, and is required to boot into a Linux environment. While the filename may vary across Linux distributions, e.g. <code>vmlinuz-6.15.9-201.fc42.x86_64</code><ref>[https://koji.fedoraproject.org/koji/rpminfo?rpmID=43854624 Information for RPM kernel-core-6.15.9-201.fc42.x86_64.rpm - Fedora buildsystem - koji.fedoraproject.org]</ref> or <code>vmlinuz-linux</code><ref>[https://bbs.archlinux.org/viewtopic.php?pid=2101137#p2101137 (SOLVED) What creates /boot/vmlinuz-linux ? - bbs.archlinux.org]</ref> the filename generally starts with <code>vmlinuz</code>.
+'''vmlinuz''' is a file comprising of [[Executable and Linkable Format|Executable and Linkable Format (ELF)]] and [[COFF|Common Object File Format (COFF)]], that contains a pre-compiled, (typically) compressed [[Linux]] kernel image, and is required to boot into a Linux environment. While the filename may vary across Linux distributions, e.g. <code>vmlinuz-6.15.9-201.fc42.x86_64</code><ref>[https://koji.fedoraproject.org/koji/rpminfo?rpmID=43854624 Information for RPM kernel-core-6.15.9-201.fc42.x86_64.rpm - Fedora buildsystem - koji.fedoraproject.org]</ref> or <code>vmlinuz-linux</code><ref>[https://bbs.archlinux.org/viewtopic.php?pid=2101137#p2101137 (SOLVED) What creates /boot/vmlinuz-linux ? - bbs.archlinux.org]</ref> the filename generally starts with <code>vmlinuz</code>.
 This file is also commonly paired with [[initramfs]], residing in <code>/boot</code> directory, enables loading of extra kernel objects (<code>.ko</code>)<ref>[https://unix.stackexchange.com/a/424603 Is "update-initramfs -u" needed after adding or removing a module with "modprobe"? - Unix & Linux Stack Exchange]</ref> along with any other added data that is necessary to;
@@ Line 27: / Line 27: @@
 * [[XZ]],
 * [[Zstandard]]
 == Identification ==
@@ Line 37: / Line 38: @@
 ** [[File command|<code>file</code>]] - Used to identify the type of file by its magic bytes
 ** [https://raw.githubusercontent.com/torvalds/linux/master/scripts/extract-vmlinux <code>extract-vmlinux</code>] - From Linus Torvald's Linux kernel repository. Used to extract vmlinuz
-** [https://www.gnu.org/software/binutils/ GNU Binutils] → objdump - For examining the [[Executable and Linkable Format|ELF]]
+** [https://www.gnu.org/software/binutils/ GNU Binutils] → objdump - For examining the file
-** [https://www.gnu.org/software/binutils/ GNU Binutils] → readelf - For examining the [[Executable and Linkable Format|ELF]]
+** [https://www.gnu.org/software/binutils/ GNU Binutils] → readelf - For examining the [[Executable and Linkable Format|ELF]] portion of the file
 == Links ==

Vmlinuz - Revision history

Anonymoususer852: vmlinuz actually also contains COFF. Also discuss about vmlinux versus vmlinuz.

Anonymoususer852: Created page with "{{FormatInfo |name=vmlinuz |formattype=electronic |subcat=Executables |extensions={{noext}} |compression=lossless }} '''vmlinuz''' is a ELF..."