Editing Vmlinux (section)

==bzImage==
[[Image:Anatomy-of-bzimage.png|thumb|Anatomy of a bzImage]]

As the Linux kernel matured, the size of the kernels generated by users grew beyond the limits imposed by some architectures, where the space available to store the compressed kernel code is limited. The bzImage (''big zImage'') format was developed to overcome this limitation by splitting the kernel over non-contiguous [[computer storage|memory]] regions.{{citation needed|date=October 2018}}

The bzImage was compressed using [[gzip]] until Linux 2.6.30,<ref name="linux-2.6.30_compression" /> which [[#Compression|introduced more algorithms]]. Although the <code>bz</code> [[prefix (linguistics)|prefix]] may suggest that [[bzip2]] compression is used, this is not the case.<ref name="linfo"/> (The bzip2 package is often distributed with tools prefixed with <code>bz</code>, such as <code>bzless</code>, <code>bzcat</code>, etc.)

The bzImage file is in a specific format. It contains concatenated <code>bootsect.o</code> + <code>setup.o</code> + <code>misc.o</code> + <code>piggy.o</code>.<ref>{{cite mailing list
 | url         = https://lkml.org/lkml/1999/9/28/29
 | title       = Re: bzImage decompression
 | date        = 1999-09-28
 | mailing-list = [[Linux kernel mailing list|LKML]]
 | author      = Yann Droneaud
 | quote       = The zImage contain bootsect.o + setup.o + misc.o + piggy.o}}</ref> <code>piggy.o</code> contains the gzipped vmlinux file in its data section. The script <code>extract-vmlinux</code> found under <code>scripts/</code> in the kernel sources decompresses a kernel image. Some distributions (e.g. [[Red Hat]] and clones) may come with a <code>kernel-debuginfo</code> [[RPM Package Manager|RPM]] that contains the <code>vmlinux</code> file for the matching kernel RPM, and it typically gets installed under <code>/usr/lib/debug/lib/modules/`uname -r`/vmlinux</code> or <code>/usr/lib/debug/lib64/modules/`uname -r`/vmlinux</code>.