os-release, initrd-release, extension-release — Operating system identification
/etc/os-release
/usr/lib/os-release
/etc/initrd-release
/usr/lib/extension-release.d/extension-release.IMAGE
The /etc/os-release and
/usr/lib/os-release files contain operating
system identification data.
The format of os-release is a newline-separated list of
environment-like shell-compatible variable assignments. It is possible to source the configuration from
Bourne shell scripts, however, beyond mere variable assignments, no shell features are supported (this
means variable expansion is explicitly not supported), allowing applications to read the file without
implementing a shell compatible execution engine. Variable assignment values must be enclosed in double
or single quotes if they include spaces, semicolons or other special characters outside of A–Z, a–z,
0–9. (Assignments that do not include these special characters may be enclosed in quotes too, but this is
optional.) Shell special characters ("$", quotes, backslash, backtick) must be escaped with backslashes,
following shell style. All strings should be in UTF-8 encoding, and non-printable characters should not
be used. Concatenation of multiple individually quoted strings is not supported. Lines beginning with "#"
are treated as comments. Blank lines are permitted and ignored.
The file /etc/os-release takes
precedence over /usr/lib/os-release.
Applications should check for the former, and exclusively use its
data if it exists, and only fall back to
/usr/lib/os-release if it is missing.
Applications should not read data from both files at the same
time. /usr/lib/os-release is the recommended
place to store OS release information as part of vendor trees.
/etc/os-release should be a relative symlink
to /usr/lib/os-release, to provide
compatibility with applications only looking at
/etc/. A relative symlink instead of an
absolute symlink is necessary to avoid breaking the link in a
chroot or initrd environment such as dracut.
os-release contains data that is
defined by the operating system vendor and should generally not be
changed by the administrator.
As this file only encodes names and identifiers it should not be localized.
The /etc/os-release and
/usr/lib/os-release files might be symlinks
to other files, but it is important that the file is available
from earliest boot on, and hence must be located on the root file
system.
os-release must not contain repeating keys. Nevertheless, readers should pick
the entries later in the file in case of repeats, similarly to how a shell sourcing the file would. A
reader may warn about repeating entries.
For a longer rationale for os-release
please refer to the Announcement of /etc/os-release.
/etc/initrd-release¶In the initrd,
/etc/initrd-release plays the same role as os-release in the
main system. Additionally, the presence of that file means that the system is in the initrd phase.
/etc/os-release should be symlinked to /etc/initrd-release
(or vice versa), so programs that only look for /etc/os-release (as described
above) work correctly.
The rest of this document that talks about os-release should be understood
to apply to initrd-release too.
/usr/lib/extension-release.d/extension-release.IMAGE¶/usr/lib/extension-release.d/extension-release.
plays the same role for extension images as IMAGEos-release for the main system, and
follows the syntax and rules as described in the Portable Services page. The purpose of this
file is to identify the extension and to allow the operating system to verify that the extension image
matches the base OS. This is typically implemented by checking that the ID= options
match, and either SYSEXT_LEVEL= exists and matches too, or if it is not present,
VERSION_ID= exists and matches. This ensures ABI/API compatibility between the
layers and prevents merging of an incompatible image in an overlay.
In order to identify the extension image itself, the same fields defined below can be added to the
extension-release file with a SYSEXT_ prefix (to disambiguate
from fields used to match on the base image). E.g.: SYSEXT_ID=myext,
SYSEXT_VERSION_ID=1.2.3.
In the extension-release. filename, the
IMAGEIMAGE part must exactly match the file name of the containing image with the
suffix removed. In case it is not possible to guarantee that an image file name is stable and doesn't
change between the build and the deployment phases, it is possible to relax this check: if exactly one
file whose name matches "extension-release.*user.extension-release.strict
xattr(7) set to the
string "0", it will be used instead.
The rest of this document that talks about os-release should be understood
to apply to extension-release too.
The following OS identifications parameters may be set using
os-release:
NAME=¶A string identifying the operating system, without a version component, and
suitable for presentation to the user. If not set, a default of "NAME=Linux" may
be used.
Examples: "NAME=Fedora", "NAME="Debian GNU/Linux"".
ID=¶A lower-case string (no spaces or other characters outside of 0–9, a–z, ".", "_"
and "-") identifying the operating system, excluding any version information and suitable for
processing by scripts or usage in generated filenames. If not set, a default of
"ID=linux" may be used. Note that even though this string may not include
characters that require shell quoting, quoting may nevertheless be used.
Examples: "ID=fedora", "ID=debian".
ID_LIKE=¶A space-separated list of operating system identifiers in the same syntax as the
ID= setting. It should list identifiers of operating systems that are closely
related to the local operating system in regards to packaging and programming interfaces, for
example listing one or more OS identifiers the local OS is a derivative from. An OS should
generally only list other OS identifiers it itself is a derivative of, and not any OSes that are
derived from it, though symmetric relationships are possible. Build scripts and similar should
check this variable if they need to identify the local operating system and the value of
ID= is not recognized. Operating systems should be listed in order of how
closely the local operating system relates to the listed ones, starting with the closest. This
field is optional.
Examples: for an operating system with "ID=centos", an assignment of
"ID_LIKE="rhel fedora"" would be appropriate. For an operating system with
"ID=ubuntu", an assignment of "ID_LIKE=debian" is appropriate.
PRETTY_NAME=¶A pretty operating system name in a format suitable for presentation to the
user. May or may not contain a release code name or OS version of some kind, as suitable. If not
set, a default of "PRETTY_NAME="Linux"" may be used
Example: "PRETTY_NAME="Fedora 17 (Beefy Miracle)"".
CPE_NAME=¶A CPE name for the operating system, in URI binding syntax, following the Common Platform Enumeration Specification as proposed by the NIST. This field is optional.
Example: "CPE_NAME="cpe:/o:fedoraproject:fedora:17""
VARIANT=¶A string identifying a specific variant or edition of the operating system suitable for presentation to the user. This field may be used to inform the user that the configuration of this system is subject to a specific divergent set of rules or default configuration settings. This field is optional and may not be implemented on all systems.
Examples: "VARIANT="Server Edition"", "VARIANT="Smart Refrigerator
Edition"".
Note: this field is for display purposes only. The VARIANT_ID field should
be used for making programmatic decisions.
VARIANT_ID=¶A lower-case string (no spaces or other characters outside of 0–9, a–z, ".", "_" and "-"), identifying a specific variant or edition of the operating system. This may be interpreted by other packages in order to determine a divergent default configuration. This field is optional and may not be implemented on all systems.
Examples: "VARIANT_ID=server", "VARIANT_ID=embedded".
VERSION=¶A string identifying the operating system version, excluding any OS name information, possibly including a release code name, and suitable for presentation to the user. This field is optional.
Examples: "VERSION=17", "VERSION="17 (Beefy Miracle)"".
VERSION_ID=¶A lower-case string (mostly numeric, no spaces or other characters outside of 0–9, a–z, ".", "_" and "-") identifying the operating system version, excluding any OS name information or release code name, and suitable for processing by scripts or usage in generated filenames. This field is optional.
Examples: "VERSION_ID=17", "VERSION_ID=11.04".
VERSION_CODENAME=¶A lower-case string (no spaces or other characters outside of 0–9, a–z, ".", "_" and "-") identifying the operating system release code name, excluding any OS name information or release version, and suitable for processing by scripts or usage in generated filenames. This field is optional and may not be implemented on all systems.
Examples: "VERSION_CODENAME=buster",
"VERSION_CODENAME=xenial".
BUILD_ID=¶A string uniquely identifying the system image originally used as the installation
base. In most cases, VERSION_ID or
IMAGE_ID+IMAGE_VERSION are updated when the entire system
image is replaced during an update. BUILD_ID may be used in distributions where
the original installation image version is important: VERSION_ID would change
during incremental system updates, but BUILD_ID would not. This field is
optional.
Examples: "BUILD_ID="2013-03-20.3"", "BUILD_ID=201303203".
IMAGE_ID=¶A lower-case string (no spaces or other characters outside of 0–9, a–z, ".", "_" and "-"), identifying a specific image of the operating system. This is supposed to be used for environments where OS images are prepared, built, shipped and updated as comprehensive, consistent OS images. This field is optional and may not be implemented on all systems, in particularly not on those that are not managed via images but put together and updated from individual packages and on the local system.
Examples: "IMAGE_ID=vendorx-cashier-system",
"IMAGE_ID=netbook-image".
IMAGE_VERSION=¶A lower-case string (mostly numeric, no spaces or other characters outside of 0–9,
a–z, ".", "_" and "-") identifying the OS image version. This is supposed to be used together with
IMAGE_ID described above, to discern different versions of the same image.
Examples: "IMAGE_VERSION=33", "IMAGE_VERSION=47.1rc1".
To summarize: if the image updates are built and shipped as comprehensive units,
IMAGE_ID+IMAGE_VERSION is the best fit. Otherwise, if updates
eventually completely replace previously installed contents, as in a typical binary distribution,
VERSION_ID should be used to identify major releases of the operating system.
BUILD_ID may be used instead or in addition to VERSION_ID when
the original system image version is important.
HOME_URL=, DOCUMENTATION_URL=, SUPPORT_URL=, BUG_REPORT_URL=, PRIVACY_POLICY_URL=¶Links to resources on the Internet related to the operating system.
HOME_URL= should refer to the homepage of the operating system, or alternatively
some homepage of the specific version of the operating system.
DOCUMENTATION_URL= should refer to the main documentation page for this
operating system. SUPPORT_URL= should refer to the main support page for the
operating system, if there is any. This is primarily intended for operating systems which vendors
provide support for. BUG_REPORT_URL= should refer to the main bug reporting page
for the operating system, if there is any. This is primarily intended for operating systems that
rely on community QA. PRIVACY_POLICY_URL= should refer to the main privacy
policy page for the operating system, if there is any. These settings are optional, and providing
only some of these settings is common. These URLs are intended to be exposed in "About this system"
UIs behind links with captions such as "About this Operating System", "Obtain Support", "Report a
Bug", or "Privacy Policy". The values should be in RFC3986 format, and should be
"http:" or "https:" URLs, and possibly "mailto:"
or "tel:". Only one URL shall be listed in each setting. If multiple resources
need to be referenced, it is recommended to provide an online landing page linking all available
resources.
Examples: "HOME_URL="https://fedoraproject.org/"",
"BUG_REPORT_URL="https://bugzilla.redhat.com/"".
SUPPORT_END=¶The date at which support for this version of the OS ends. (What exactly "lack of
support" means varies between vendors, but generally users should assume that updates, including
security fixes, will not be provided.) The value is a date in the ISO 8601 format
"YYYY-MM-DD", and specifies the first day on which support is
not provided.
For example, "SUPPORT_END=2001-01-01" means that the system was supported
until the end of the last day of the previous millennium.
LOGO=¶A string, specifying the name of an icon as defined by freedesktop.org Icon Theme Specification. This can be used by graphical applications to display an operating system's or distributor's logo. This field is optional and may not necessarily be implemented on all systems.
Examples: "LOGO=fedora-logo", "LOGO=distributor-logo-opensuse"
ANSI_COLOR=¶A suggested presentation color when showing the OS name on the console. This should be specified as string suitable for inclusion in the ESC [ m ANSI/ECMA-48 escape code for setting graphical rendition. This field is optional.
Examples: "ANSI_COLOR="0;31"" for red, "ANSI_COLOR="1;34""
for light blue, or "ANSI_COLOR="0;38;2;60;110;180"" for Fedora blue.
VENDOR_NAME=¶The name of the OS vendor. This is the name of the organization or company which produces the OS. This field is optional.
This name is intended to be exposed in "About this system" UIs or software update UIs when needed to distinguish the OS vendor from the OS itself. It is intended to be human readable.
Examples: "VENDOR_NAME="Fedora Project"" for Fedora Linux,
"VENDOR_NAME="Canonical"" for Ubuntu.
VENDOR_URL=¶The homepage of the OS vendor. This field is optional. The
VENDOR_NAME= field should be set if this one is, although clients must be
robust against either field not being set.
The value should be in RFC3986 format, and should be
"http:" or "https:" URLs. Only one URL shall be listed in the
setting.
Examples: "VENDOR_URL="https://fedoraproject.org/"",
"VENDOR_URL="https://canonical.com/"".
DEFAULT_HOSTNAME=¶A string specifying the hostname if hostname(5) is not present and no other configuration source specifies the hostname. Must be either a single DNS label (a string composed of 7-bit ASCII lower-case characters and no spaces or dots, limited to the format allowed for DNS domain name labels), or a sequence of such labels separated by single dots that forms a valid DNS FQDN. The hostname must be at most 64 characters, which is a Linux limitation (DNS allows longer names).
See org.freedesktop.hostname1(5) for a description of how systemd-hostnamed.service(8) determines the fallback hostname.
ARCHITECTURE=¶A string that specifies which CPU architecture the userspace binaries require.
The architecture identifiers are the same as for ConditionArchitecture=
described in systemd.unit(5).
The field is optional and should only be used when just single architecture is supported.
It may provide redundant information when used in a GPT partition with a GUID type that already
encodes the architecture. If this is not the case, the architecture should be specified in
e.g., an extension image, to prevent an incompatible host from loading it.
SYSEXT_LEVEL=¶A lower-case string (mostly numeric, no spaces or other characters outside of 0–9,
a–z, ".", "_" and "-") identifying the operating system extensions support level, to indicate which
extension images are supported. See /usr/lib/extension-release.d/extension-release.,
initrd and
systemd-sysext(8))
for more information.IMAGE
Examples: "SYSEXT_LEVEL=2", "SYSEXT_LEVEL=15.14".
CONFEXT_LEVEL=¶Semantically the same as SYSEXT_LEVEL= but for confext images.
See /etc/extension-release.d/extension-release.
for more information.IMAGE
Examples: "CONFEXT_LEVEL=2", "CONFEXT_LEVEL=15.14".
SYSEXT_SCOPE=¶Takes a space-separated list of one or more of the strings
"system", "initrd" and "portable". This field is
only supported in extension-release.d/ files and indicates what environments
the system extension is applicable to: i.e. to regular systems, to initrds, or to portable service
images. If unspecified, "SYSEXT_SCOPE=system portable" is implied, i.e. any system
extension without this field is applicable to regular systems and to portable service environments,
but not to initrd environments.
CONFEXT_SCOPE=¶Semantically the same as SYSEXT_SCOPE= but for confext images.
PORTABLE_PREFIXES=¶Takes a space-separated list of one or more valid prefix match strings for the Portable Services logic. This field serves two purposes: it is informational, identifying portable service images as such (and thus allowing them to be distinguished from other OS images, such as bootable system images). It is also used when a portable service image is attached: the specified or implied portable service prefix is checked against the list specified here, to enforce restrictions how images may be attached to a system.
If you are using this file to determine the OS or a specific version of it, use the
ID and VERSION_ID fields, possibly with
ID_LIKE as fallback for ID. When looking for an OS identification
string for presentation to the user use the PRETTY_NAME field.
Note that operating system vendors may choose not to provide version information, for example to
accommodate for rolling releases. In this case, VERSION and
VERSION_ID may be unset. Applications should not rely on these fields to be
set.
Operating system vendors may extend the file format and introduce new fields. It is highly recommended to prefix new fields with an OS specific name in order to avoid name clashes. Applications reading this file must ignore unknown fields.
Example: "DEBIAN_BTS="debbugs://bugs.debian.org/"".
Container and sandbox runtime managers may make the host's identification data available to
applications by providing the host's /etc/os-release (if available, otherwise
/usr/lib/os-release as a fallback) as
/run/host/os-release.
Example 1. os-release file for Fedora Workstation
NAME=Fedora VERSION="32 (Workstation Edition)" ID=fedora VERSION_ID=32 PRETTY_NAME="Fedora 32 (Workstation Edition)" ANSI_COLOR="0;38;2;60;110;180" LOGO=fedora-logo-icon CPE_NAME="cpe:/o:fedoraproject:fedora:32" HOME_URL="https://fedoraproject.org/" DOCUMENTATION_URL="https://docs.fedoraproject.org/en-US/fedora/f32/system-administrators-guide/" SUPPORT_URL="https://fedoraproject.org/wiki/Communicating_and_getting_help" BUG_REPORT_URL="https://bugzilla.redhat.com/" REDHAT_BUGZILLA_PRODUCT="Fedora" REDHAT_BUGZILLA_PRODUCT_VERSION=32 REDHAT_SUPPORT_PRODUCT="Fedora" REDHAT_SUPPORT_PRODUCT_VERSION=32 PRIVACY_POLICY_URL="https://fedoraproject.org/wiki/Legal:PrivacyPolicy" VARIANT="Workstation Edition" VARIANT_ID=workstation
Example 3. Reading os-release in
sh(1)
#!/bin/sh -eu
# SPDX-License-Identifier: MIT-0
test -e /etc/os-release && os_release='/etc/os-release' || os_release='/usr/lib/os-release'
. "${os_release}"
echo "Running on ${PRETTY_NAME:-Linux}"
if [ "${ID:-linux}" = "debian" ] || [ "${ID_LIKE#*debian*}" != "${ID_LIKE}" ]; then
echo "Looks like Debian!"
fi
Example 4. Reading os-release in
python(1) (versions >= 3.10)
#!/usr/bin/python
# SPDX-License-Identifier: MIT-0
import platform
os_release = platform.freedesktop_os_release()
pretty_name = os_release.get('PRETTY_NAME', 'Linux')
print(f'Running on {pretty_name!r}')
if 'fedora' in [os_release.get('ID', 'linux'),
*os_release.get('ID_LIKE', '').split()]:
print('Looks like Fedora!')
See docs for
platform.freedesktop_os_release for more details.
Example 5. Reading os-release in
python(1) (any version)
#!/usr/bin/python
# SPDX-License-Identifier: MIT-0
import ast
import re
import sys
def read_os_release():
try:
filename = '/etc/os-release'
f = open(filename)
except FileNotFoundError:
filename = '/usr/lib/os-release'
f = open(filename)
for line_number, line in enumerate(f, start=1):
line = line.rstrip()
if not line or line.startswith('#'):
continue
m = re.match(r'([A-Z][A-Z_0-9]+)=(.*)', line)
if m:
name, val = m.groups()
if val and val[0] in '"\'':
val = ast.literal_eval(val)
yield name, val
else:
print(f'{filename}:{line_number}: bad line {line!r}',
file=sys.stderr)
os_release = dict(read_os_release())
pretty_name = os_release.get('PRETTY_NAME', 'Linux')
print(f'Running on {pretty_name!r}')
if 'debian' in [os_release.get('ID', 'linux'),
*os_release.get('ID_LIKE', '').split()]:
print('Looks like Debian!')
Note that the above version that uses the built-in implementation is preferred in most cases, and the open-coded version here is provided for reference.