This section is for additional requirements and recommendations that only apply to a specific operating system. The material in this section should never conflict with the base standard.

This is the annex for the Linux operating system.

On Linux systems, if the kernel is located in /, we recommend using the names vmlinux or vmlinuz, which have been used in recent Linux kernel source packages.

Linux systems which require them place these additional files into /bin: setserial

The following devices must exist under /dev. /dev/null All data written to this device is discarded. A read from this device will return an EOF condition. /dev/zero This device is a source of zeroed out data. All data written to this device is discarded. A read from this device will return as many bytes containing the value zero as was requested. /dev/tty This device is a synonym for the controlling terminal of a process. Once this device is opened, all reads and writes will behave as if the actual controlling terminal device had been opened. Previous versions of the FHS had stricter requirements for /dev. Other devices may also exist in /dev. Device names may exist as symbolic links to other device nodes located in /dev or subdirectories of /dev. There is no requirement concerning major/minor number values.

Linux systems which require them place these additional files into /etc. lilo.conf

The 64-bit architectures PPC64, s390x, sparc64 and AMD64 must place 64-bit libraries in /lib64, and 32-bit (or 31-bit on s390) libraries in /lib. The 64-bit architecture IA64 must place 64-bit libraries in /lib. This is a refinement of the general rules for /lib<qual> and /usr/lib<qual>. The architectures PPC64, s390x, sparc64 and AMD64 support support both 32-bit (for s390 more precise 31-bit) and 64-bit programs. Using lib for 32-bit binaries allows existing binaries from the 32-bit systems to work without any changes: such binaries are expected to be numerous. IA-64 uses a different scheme, reflecting the deprecation of 32-bit binaries (and hence libraries) on that architecture.

The proc filesystem is the de-facto standard Linux method for handling process and system information, rather than /dev/kmem and other similar methods. We strongly encourage this for the storage and retrieval of process information as well as other kernel and memory information.

Linux systems place these additional files into /sbin. Second extended filesystem commands (optional): badblocks dumpe2fs e2fsck mke2fs mklost+found tune2fs Boot-loader map installer (optional): lilo Optional files for /sbin: Static binaries: ldconfig sln ssync Static ln (sln) and static sync (ssync) are useful when things go wrong. The primary use of sln (to repair incorrect symlinks in /lib after a poorly orchestrated upgrade) is no longer a major concern now that the ldconfig program (usually located in /usr/sbin) exists and can act as a guiding hand in upgrading the dynamic libraries. Static sync is useful in some emergency situations. Note that these need not be statically linked versions of the standard ln and sync, but may be. The ldconfig binary is optional for /sbin since a site may choose to run ldconfig at boot time, rather than only when upgrading the shared libraries. (It's not clear whether or not it is advantageous to run ldconfig on each boot.) Even so, some people like ldconfig around for the following (all too common) situation: I've just removed /lib/<file>. I can't find out the name of the library because ls is dynamically linked, I'm using a shell that doesn't have ls built-in, and I don't know about using "echo *" as a replacement. I have a static sln, but I don't know what to call the link. Miscellaneous: ctrlaltdel kbdrate So as to cope with the fact that some keyboards come up with such a high repeat rate as to be unusable, kbdrate may be installed in /sbin on some systems. Since the default action in the kernel for the Ctrl-Alt-Del key combination is an instant hard reboot, it is generally advisable to disable the behavior before mounting the root filesystem in read-write mode. Some init suites are able to disable Ctrl-Alt-Del, but others may require the ctrlaltdel program, which may be installed in /sbin on those systems.

These symbolic links are required if a C or C++ compiler is installed and only for systems not based on glibc. /usr/include/asm -> /usr/src/linux/include/asm-<arch> /usr/include/linux -> /usr/src/linux/include/linux

For systems based on glibc, there are no specific guidelines for this directory. For systems based on Linux libc revisions prior to glibc, the following guidelines and rationale apply: The only source code that should be placed in a specific location is the Linux kernel source code. It is located in /usr/src/linux. If a C or C++ compiler is installed, but the complete Linux kernel source code is not installed, then the include files from the kernel source code must be located in these directories: /usr/src/linux/include/asm-<arch> /usr/src/linux/include/linux <arch> is the name of the system architecture. /usr/src/linux may be a symbolic link to a kernel source code tree. It is important that the kernel include files be located in /usr/src/linux and not in /usr/include so there are no problems when system administrators upgrade their kernel version for the first time.

This directory contains the variable data for the cron and at programs.