Table of Contents
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/nullAll data written to this device is discarded. A read from this device will return an EOF condition.
/dev/zeroThis 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/ttyThis 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 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 commands relating to filesystem maintenance and
boot loader management into /sbin.
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.
The sys filesystem
is the location where
information about devices, drivers, and some kernel features is
exposed. Its underlying structure is determined by the particular
Linux kernel being used at the moment, and is otherwise
unspecified.
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.