systemd prerelease 248-rc4
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systemd tag bot
2021-03-17 22:31:53 UTC
A new systemd ☠️ pre-release ☠️ has just been tagged. Please download the tarball here:


NOTE: This is ☠️ pre-release ☠️ software. Do not run this on production
systems, but please test this and report any issues you find to GitHub:


Changes since the previous release:

* A concept of system extension images is introduced. Such images may
be used to extend the /usr/ and /opt/ directory hierarchies at
runtime with additional files (even if the file system is read-only).
When a system extension image is activated, its /usr/ and /opt/
hierarchies and os-release information are combined via overlayfs
with the file system hierarchy of the host OS.

A new systemd-sysext tool can be used to merge, unmerge, list, and
refresh system extension hierarchies. See

The systemd-sysext.service automatically merges installed system
extensions during boot (before basic.target, but not in very early
boot, since various file systems have to be mounted first).

The SYSEXT_LEVEL= field in os-release(5) may be used to specify the
supported system extension level.

* A new ExtensionImages= unit setting can be used to apply the same
system extension image concept from systemd-sysext to the namespaced
file hierarchy of specific services, following the same rules and

* Support for a new special "root=tmpfs" kernel command-line option has
been added. When specified, a tmpfs is mounted on /, and mount.usr=
should be used to point to the operating system implementation.

* A new configuration file /etc/veritytab may be used to configure
dm-verity integrity protection for block devices. Each line is in the
format "volume-name data-device hash-device roothash options",
similar to /etc/crypttab.

* A new kernel command-line option systemd.verity.root_options= may be
used to configure dm-verity behaviour for the root device.

* The key file specified in /etc/crypttab (the third field) may now
refer to an AF_UNIX/SOCK_STREAM socket in the file system. The key is
acquired by connecting to that socket and reading from it. This
allows the implementation of a service to provide key information
dynamically, at the moment when it is needed.

* When the hostname is set explicitly to "localhost", systemd-hostnamed
will respect this. Previously such a setting would be mostly silently
ignored. The goal is to honour configuration as specified by the

* The fallback hostname that will be used by the system manager and
systemd-hostnamed can now be configured in two new ways: by setting
DEFAULT_HOSTNAME= in os-release(5), or by setting
$SYSTEMD_DEFAULT_HOSTNAME in the environment block. As before, it can
also be configured during compilation. The environment variable is
intended for testing and local overrides, the os-release(5) field is
intended to allow customization by different variants of a
distribution that share the same compiled packages.

* The environment block of the manager itself may be configured through
a new ManagerEnvironment= setting in system.conf or user.conf. This
complements existing ways to set the environment block (the kernel
command line for the system manager, the inherited environment and
***@.service unit file settings for the user manager).

* systemd-hostnamed now exports the default hostname and the source of
the configured hostname ("static", "transient", or "default") as
D-Bus properties.

* systemd-hostnamed now exports the "HardwareVendor" and
"HardwareModel" D-Bus properties, which are supposed to contain a
pair of cleaned up, human readable strings describing the system's
vendor and model. It's typically sourced from the firmware's DMI
tables, but may be augmented from a new hwdb database. hostnamectl
shows this in the status output.

* Support has been added to systemd-cryptsetup for extracting the
PKCS#11 token URI and encrypted key from the LUKS2 JSON embedded
metadata header. This allows the information how to open the
encrypted device to be embedded directly in the device and obviates
the need for configuration in an external file.

* systemd-cryptsetup gained support for unlocking LUKS2 volumes using
TPM2 hardware, as well as FIDO2 security tokens (in addition to the
pre-existing support for PKCS#11 security tokens).

* systemd-repart may enroll encrypted partitions using TPM2
hardware. This may be useful for example to create an encrypted /var
partition bound to the machine on first boot.

* A new systemd-cryptenroll tool has been added to enroll TPM2, FIDO2
and PKCS#11 security tokens to LUKS volumes, list and destroy
them. See:


It also supports enrolling "recovery keys" and regular passphrases.

* The libfido2 dependency is now based on dlopen(), so that the library
is used at runtime when installed, but is not a hard runtime

* systemd-cryptsetup gained support for two new options in
/etc/crypttab: "no-write-workqueue" and "no-read-workqueue" which
request synchronous processing of encryption/decryption IO.

* The manager may be configured at compile time to use the fexecve()
instead of the execve() system call when spawning processes. Using
fexecve() closes a window between checking the security context of an
executable and spawning it, but unfortunately the kernel displays
stale information in the process' "comm" field, which impacts ps
output and such.

* The configuration option -Dcompat-gateway-hostname has been dropped.
"_gateway" is now the only supported name.

* The ConditionSecurity=tpm2 unit file setting may be used to check if
the system has at least one TPM2 (tpmrm class) device.

* A new ConditionCPUFeature= has been added that may be used to
conditionalize units based on CPU features. For example,
ConditionCPUFeature=rdrand will condition a unit so that it is only
run when the system CPU supports the RDRAND opcode.

* The existing ConditionControlGroupController= setting has been
extended with two new values "v1" and "v2". "v2" means that the
unified v2 cgroup hierarchy is used, and "v1" means that legacy v1
hierarchy or the hybrid hierarchy are used.

* A new PrivateIPC= setting on a unit file allows executed processes to
be moved into a private IPC namespace, with separate System V IPC
identifiers and POSIX message queues.

A new IPCNamespacePath= allows the unit to be joined to an existing
IPC namespace.

* The tables of system calls in seccomp filters are now automatically
generated from kernel lists exported on

The following architectures should now have complete lists:
alpha, arc, arm64, arm, i386, ia64, m68k, mips64n32, mips64, mipso32,
powerpc, powerpc64, s390, s390x, tilegx, sparc, x86_64, x32.

* The MountAPIVFS= service file setting now additionally mounts a tmpfs
on /run/ if it is not already a mount point. A writable /run/ has
always been a requirement for a functioning system, but this was not
guaranteed when using a read-only image.

Users can always specify BindPaths= or InaccessiblePaths= as
overrides, and they will take precedence. If the host's root mount
point is used, there is no change in behaviour.

* New bind mounts and file system image mounts may be injected into the
mount namespace of a service (without restarting it). This is exposed
respectively as 'systemctl bind <unit> <path>…' and
'systemctl mount-image <unit> <image>…'.

* The StandardOutput= and StandardError= settings can now specify files
to be truncated for output (as "truncate:<path>").

* The ExecPaths= and NoExecPaths= settings may be used to specify
noexec for parts of the file system.

* sd-bus has a new function sd_bus_open_user_machine() to open a
connection to the session bus of a specific user in a local container
or on the local host. This is exposed in the existing -M switch to
systemctl and similar tools:

systemctl --user -M ***@foobar start foo

This will connect to the user bus of a user "lennart" in container
"foobar". If no container name is specified, the specified user on
the host itself is connected to

systemctl --user -M lennart@ start quux

* sd-bus also gained a convenience function sd_bus_message_send() to
simplify invocations of sd_bus_send(), taking only a single
parameter: the message to send.

* sd-event allows rate limits to be set on event sources, for dealing
with high-priority event sources that might starve out others. See
the new man page sd_event_source_set_ratelimit(3) for details.

* systemd.link files gained a [Link] Promiscuous= switch, which allows
the device to be raised in promiscuous mode.

New [Link] TransmitQueues= and ReceiveQueues= settings allow the
number of TX and RX queues to be configured.

New [Link] TransmitQueueLength= setting allows the size of the TX
queue to be configured.

New [Link] GenericSegmentOffloadMaxBytes= and
GenericSegmentOffloadMaxSegments= allow capping the packet size and
the number of segments accepted in Generic Segment Offload.

* systemd-networkd gained support for the "B.A.T.M.A.N. advanced"
wireless routing protocol that operates on ISO/OSI Layer 2 only and
uses ethernet frames to route/bridge packets. This encompasses a new
"batadv" netdev Type=, a new [BatmanAdvanced] section with a bunch of
new settings in .netdev files, and a new BatmanAdvanced= setting in
.network files.

* systemd.network files gained a [Network] RouteTable= configuration
switch to select the routing policy table.

systemd.network files gained a [RoutingPolicyRule] Type=
configuration switch (one of "blackhole, "unreachable", "prohibit").

systemd.network files gained a [IPv6AcceptRA] RouteDenyList= and
RouteAllowList= settings to ignore/accept route advertisements from
routers matching specified prefixes. The DenyList= setting has been
renamed to PrefixDenyList= and a new PrefixAllowList= option has been

systemd.network files gained a [DHCPv6] UseAddress= setting to
optionally ignore the address provided in the lease.

systemd.network files gained a [DHCPv6PrefixDelegation]
ManageTemporaryAddress= switch.

systemd.network files gained a new ActivationPolicy= setting which
allows configuring how the UP state of an interface shall be managed,
i.e. whether the interface is always upped, always downed, or may be
upped/downed by the user using "ip dev".

* The default for the Broadcast= setting in .network files has slightly
changed: the broadcast address will not be configured for wireguard

* systemd.netdev files gained a [VLAN] Protocol=, IngressQOSMaps=,
EgressQOSMaps=, and [MACVLAN] BroadcastMulticastQueueLength=
configuration options for VLAN packet handling.

* udev rules may now set log_level= option. This allows debug logs to
be enabled for select events, e.g. just for a specific subsystem or
even a single device.

* udev now exports the VOLUME_ID, LOGICAL_VOLUME_ID, VOLUME_SET_ID, and
DATA_PREPARED_ID properties for block devices with ISO9660 file

* udev now exports decoded DMI information about installed memory slots
as device properties under the /sys/class/dmi/id/ pseudo device.

* /dev/ is not mounted noexec anymore. This didn't provide any
significant security benefits and would conflict with the executable
mappings used with /dev/sgx device nodes. The previous behaviour can
be restored for individual services with NoExecPaths=/dev (or by allow-
listing and excluding /dev from ExecPaths=).

* Permissions for /dev/vsock are now set to 0o666, and /dev/vhost-vsock
and /dev/vhost-net are owned by the kvm group.

* The hardware database has been extended with a list of fingerprint
readers that correctly support USB auto-suspend using data from

* systemd-resolved can now answer DNSSEC questions through the stub
resolver interface in a way that allows local clients to do DNSSEC
validation themselves. For a question with DO+CD set, it'll proxy the
DNS query and respond with a mostly unmodified packet received from
the upstream server.

* systemd-resolved learnt a new boolean option CacheFromLocalhost= in
resolved.conf. If true the service will provide caching even for DNS
lookups made to an upstream DNS server on the
addresses. By default (and when the option is false) systemd-resolved
will not cache such lookups, in order to avoid duplicate local
caching, under the assumption the local upstream server caches

* systemd-resolved now implements RFC5001 NSID in its local DNS
stub. This may be used by local clients to determine whether they are
talking to the DNS resolver stub or a different DNS server.

* When resolving host names and other records resolvectl will now
report where the data was acquired from (i.e. the local cache, the
network, locally synthesized, …) and whether the network traffic it
effected was encrypted or not. Moreover the tool acquired a number of
new options --cache=, --synthesize=, --network=, --zone=,
--trust-anchor=, --validate= that take booleans and may be used to
tweak a lookup, i.e. whether it may be answered from cached
information, locally synthesized information, information acquired
through the network, the local mDNS/LLMNR zone, the DNSSEC trust
anchor, and whether DNSSEC validation shall be executed for the

* systemd-nspawn gained a new --ambient-capability= setting
(AmbientCapability= in .nspawn files) to configure ambient
capabilities passed to the container payload.

* systemd-nspawn gained the ability to configure the firewall using the
nftables subsystem (in addition to the existing iptables
support). Similarly, systemd-networkd's IPMasquerade= option now
supports nftables as back-end, too. In both cases NAT on IPv6 is now
supported too, in addition to IPv4 (the iptables back-end still is

"IPMasquerade=yes", which was the same as "IPMasquerade=ipv4" before,
retains its meaning, but has been deprecated. Please switch to either
"ivp4" or "both" (if covering IPv6 is desired).

* systemd-importd will now download .verity and .roothash.p7s files
along with the machine image (as exposed via machinectl pull-raw).

* systemd-oomd now gained a new DefaultMemoryPressureDurationSec=
setting to configure the time a unit's cgroup needs to exceed memory
pressure limits before action will be taken, and a new
ManagedOOMPreference=none|avoid|omit setting to avoid killing certain

systemd-oomd is now considered fully supported (the usual
backwards-compatiblity promises apply). Swap is not required for
operation, but it is still recommended.

* systemd-timesyncd gained a new ConnectionRetrySec= setting which
configures the retry delay when trying to contact servers.

* systemd-stdio-bridge gained --system/--user options to connect to the
system bus (previous default) or the user session bus.

* systemd-localed may now call locale-gen to generate missing locales
on-demand (UTF-8-only). This improves integration with Debian-based
distributions (Debian/Ubuntu/PureOS/Tanglu/...) and Arch Linux.

* systemctl --check-inhibitors=true may now be used to obey inhibitors
even when invoked non-interactively. The old --ignore-inhibitors
switch is now deprecated and replaced by --check-inhibitors=false.

* systemctl import-environment will now emit a warning when called
without any arguments (i.e. to import the full environment block of
the called program). This command will usually be invoked from a
shell, which means that it'll inherit a bunch of variables which are
specific to that shell, and usually to the TTY the shell is connected
to, and don't have any meaning in the global context of the system or
user service manager. Instead, only specific variables should be
imported into the manager environment block.

Similarly, programs which update the manager environment block by
directly calling the D-Bus API of the manager, should also push
specific variables, and not the full inherited environment.

* systemctl's status output now shows unit state with a more careful
choice of Unicode characters: units in maintenance show a "○" symbol
instead of the usual "●", failed units show "×", and services being
reloaded "↻".

* coredumpctl gained a --debugger-arguments= switch to pass arguments
to the debugger. It also gained support for showing coredump info in
a simple JSON format.

* systemctl/loginctl/machinectl's --signal= option now accept a special
value "list", which may be used to show a brief table with known
process signals and their numbers.

* networkctl now shows the link activation policy in status.

* Various tools gained --pager/--no-pager/--json= switches to
enable/disable the pager and provide JSON output.

* Various tools now accept two new values for the SYSTEMD_COLORS
environment variable: "16" and "256", to configure how many terminal
colors are used in output.

* less 568 or newer is now required for the auto-paging logic of the
various tools. Hyperlink ANSI sequences in terminal output are now
used even if a pager is used, and older versions of less are not able
to display these sequences correctly. SYSTEMD_URLIFY=0 may be used to
disable this output again.

* Builds with support for separate / and /usr/ hierarchies ("split-usr"
builds, non-merged-usr builds) are now officially deprecated. A
warning is emitted during build. Support is slated to be removed in
about a year (when the Debian Bookworm release development starts).

* Systems with the legacy cgroup v1 hierarchy are now marked as
"tainted", to make it clearer that using the legacy hierarchy is not

* systemd-localed will now refuse to configure a keymap which is not
installed in the file system. This is intended as a bug fix, but
could break cases where systemd-localed was used to configure the
keymap in advanced of it being installed. It is necessary to install
the keymap file first.

* The main git development branch has been renamed to 'main'.

* mmcblk[0-9]boot[0-9] devices will no longer be probed automatically
for partitions, as in the vast majority of cases they contain none
and are used internally by the bootloader (eg: uboot).

* systemd will now set the $SYSTEMD_EXEC_PID environment variable for
spawned processes to the PID of the process itself. This may be used
by programs for detecting whether they were forked off by the service
manager itself or are a process forked off further down the tree.

* The sd-device API gained four new calls: sd_device_get_action() to
determine the uevent add/remove/change/… action the device object has
been seen for, sd_device_get_seqno() to determine the uevent sequence
number, sd_device_new_from_stat_rdev() to allocate a new sd_device
object from stat(2) data of a device node, and sd_device_trigger() to
write to the 'uevent' attribute of a device.

* For most tools the --no-legend= switch has been replaced by
--legend=no and --legend=yes, to force whether tables are shown with

* Units acquired a new property "Markers" that takes a list of zero,
one or two of the following strings: "needs-reload" and
"needs-restart". These markers may be set via "systemctl
set-property". Once a marker is set, "systemctl reload-or-restart
--marked" may be invoked to execute the operation the units are
marked for. This is useful for package managers that want to mark
units for restart/reload while updating, but effect the actual
operations at a later step at once.

* The sd_bus_message_read_strv() API call of sd-bus may now also be
used to parse arrays of D-Bus signatures and D-Bus paths, in addition
to regular strings.

* bootctl will now report whether the UEFI firmware used a TPM2 device
and measured the boot process into it.

* systemd-tmpfiles learnt support for a new environment variable
$SYSTEMD_TMPFILES_FORCE_SUBVOL which takes a boolean value. If true
the v/q/Q lines in tmpfiles.d/ snippets will create btrfs subvolumes
even if the root fs of the system is not itself a btrfs volume.

* systemd-detect-virt/ConditionVirtualization= will now explicitly
detect Docker/Podman environments where possible. Moreover, they
should be able to generically detect any container manager as long as
it assigns the container a cgroup.

* portablectl gained a new "reattach" verb for detaching/reattaching a
portable service image, useful for updating images on-the-fly.

* Intel SGX enclave device nodes (which expose a security feature of
newer Intel CPUs) will now be owned by a new system group "sgx".

Contributions from: Adam Nielsen, Adrian Vovk, AJ Jordan, Alan Perry,
Alastair Pharo, Alexander Batischev, Ali Abdallah, Andrew Balmos, Anita
Zhang, Annika Wickert, Ansgar Burchardt, Antonius Frie, Ardy, Arian van
Putten, Ariel Fermani, Arnaud T, A S Alam, Bastien Nocera, Benjamin
Berg, Benjamin Robin, Björn Daase, caoxia, Carlo Wood, Charles Lee,
ChopperRob, chri2, Christian Ehrhardt, Christian Hesse, Christopher
Obbard, clayton craft, corvusnix, cprn, d032747, Daan De Meyer, Daniele
Medri, Daniel Rusek, Dan Sanders, Dan Streetman, Darren Ng, David
Edmundson, Deepak Rawat, Devon Pringle, Dmitry Borodaenko, dropsignal,
Einsler Lee, Endre Szabo, Evgeny Vereshchagin, Fabian Affolter, Felipe
Borges, feliperodriguesfr, Felix Stupp, Florian Hülsmann, Florian
Klink, Florian Westphal, Franck Bui, Frantisek Sumsal, Gablegritule,
Gaël PORTAY, Gaurav, Giedrius Statkevičius, Greg Depoire--Ferrer,
Gustavo Costa, Hans de Goede, Hela Basa, heretoenhance, Iago López
Galeiras, igo95862, Ilya Dmitrichenko, Jameer Pathan, Jan Tojnar,
Jiehong, Jinyuan Si, Joerg Behrmann, John Slade, Jonathan G. Underwood,
Jonathan McDowell, Josh Triplett, Joshua Watt, Julia Cartwright, Julien
Humbert, Kairui Song, Karel Zak, Kevin Backhouse, Kevin P. Fleming,
Khem Raj, Konomi, krissgjeng, l4gfcm, Lajos Veres, Lennart Poettering,
Luca Boccassi, Luca BRUNO, Lucas Werkmeister, Luka Kudra, Luna
Jernberg, Marc-André Lureau, Martin Wilck, Matthias Klumpp, Matt
Turner, Michael Marley, Michal Fabik, Michał Kopeć, Michal Koutný,
Michal Sekletár, Mike Gilbert, milovlad, moson-mo, Nick, nihilix-melix,
Oğuz Ersen, Ondrej Mosnacek, pali, Pavel Hrdina, Pavel Sapezhko, Perry
Yuan, Peter Hutterer, Pierre Dubouilh, Piotr Drąg, Richard Laager,
rnhmjoj, RussianNeuroMancer, Sebastiaan van Stijn, Sergey Bugaev,
shenyangyang4, simmon, Simonas Kazlauskas, Slimane Selyan Amiri, Stefan
Agner, Steve Ramage, Susant Sahani, Sven Mueller, Tad Fisher, Takashi
Iwai, Thomas Haller, Tom Shield, Topi Miettinen, Torsten Hilbrich,
Tyler Hicks, ulf-f, Ulrich Ölmann, Vincent Pelletier, Vinnie Magro,
Vito Caputo, Vlad, walbit-de, Whired Planck, wouter bolsterlee, Xℹ
Ruoyao, Yuri Chornoivan, Yu Watanabe, Zach Smith, Zbigniew
Jędrzejewski-Szmek, Zmicer Turok, Дамјан Георгиевски

— Berlin, 2021-03-17
Jan Pokorný
2021-03-20 21:34:07 UTC

perhaps not the feedback you are after (no actual testing), but some
Post by systemd tag bot
* systemd-stdio-bridge gained --system/--user options to connect to the
system bus (previous default) or the user session bus.
Is it worth detailing changes for the otherwise undocumented
tool here? See <https://github.com/systemd/systemd/issues/4784>.
Post by systemd tag bot
* systemd-localed will now refuse to configure a keymap which is not
installed in the file system. This is intended as a bug fix, but
could break cases where systemd-localed was used to configure the
keymap in advanced of it being installed. It is necessary to install
the keymap file first.
s/advanced/advance/ ?
Post by systemd tag bot
* The main git development branch has been renamed to 'main'.
Is it worth detailing development/$SCM subtleties here?

Jan (poki)