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add stuff to NEWS for 247

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Lennart Poettering 2020-10-05 11:39:35 +02:00
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NEWS
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@ -2,14 +2,14 @@ systemd System and Service Manager
CHANGES WITH 247 in spe:
* KERNEL API INCOMPATIBILTY: Linux 4.12 introduced two new uevents
* KERNEL API INCOMPATIBILITY: Linux 4.12 introduced two new uevents
"bind" and "unbind" to the Linux device model. When this kernel
change was made, systemd-udevd was only minimally updated to handle
and propagate these new event types. The introduction of these new
uevents (which are typically generated for USB devices and devices
needing a firmware upload before being functional) resulted in a
number of software issues, we so far didn't address (mostly because
there was hope the kernel maintainers would themeselves address these
there was hope the kernel maintainers would themselves address these
issues in some form – which did not happen). To handle them properly,
many (if not most) udev rules files shipped in various packages need
updating, and so do many programs that monitor or enumerate devices
@ -74,8 +74,8 @@ CHANGES WITH 247 in spe:
• Any code that uses device tags for deciding whether a device is
relevant or not most likely needs to be updated to use the new
udev_device_has_current_tag() API (or sd_device_has_current_tag()
in case sd-device is used), to check whether the tag is set
at the moment an uevent is seen (as opposed to the existing
in case sd-device is used), to check whether the tag is set at the
moment an uevent is seen (as opposed to the existing
udev_device_has_tag() API which checks if the tag ever existed on
the device, following the API concept redefinition explained
above).
@ -85,6 +85,12 @@ CHANGES WITH 247 in spe:
this is not caused by systemd/udev changes, but result of a kernel
behaviour change.
* The MountAPIVFS= service file setting now defaults to on if
RootImage= and RootDirectory= are used, ensuring that use of these
two settings ensures /proc/, /sys/ and /dev/ are properly set up for
services. By explicitly turning off these settings old behaviour may
be restored.
* Since PAM 1.2.0 (2015) configuration snippets may be placed in
/usr/lib/pam.d/ in addition to /etc/pam.d/. If a file exists in the
latter it takes precedence over the former, similar to how most of
@ -101,6 +107,377 @@ CHANGES WITH 247 in spe:
at build time, optionally undoing this change of default paths
introduced with systemd 247.
* The runtime dependencies on libqrencode, libpcre2, libpwquality and
libcryptsetup have been changed to be based on dlopen(): instead of
regular dynamic library dependencies declared in the binary ELF
headers, these libraries are now loaded on demand only, if they are
available. If the libraries cannot be found the relevant operations
will fail gracefully, or a suitable fallback logic is chosen. This is
supposed to be useful for general purpose distributions, as it allows
minimizing the list of dependencies the systemd packages pull in,
permitting building of more minimal OS images, while still making use
of these "weak" dependencies should they be installed. Since many
package managers automatically synthesize package dependencies from
ELF shared library dependencies, some additional manual packaging
work has to be done now to replace this (and the dependencies
downgraded slightly from "required" to "recommended" or whatever is
conceptually suitable for the used package manager). Note that this
change does not alter build-time behaviour: as before the build-time
dependencies have to be installed during build, even if they now are
optional during runtime.
* sd-event.h gained a new call sd_event_add_time_relative() for
installing timers relative to the current time. This is mostly a
convenience wrapper around the pre-existing sd_event_add_time() call
which installs absolute timers.
* A new per-unit setting RootImageOptions= has been added which allows
tweaking the mount options for any file system mounted as effect of
the RootImage= setting.
* Another new per-unit setting MountImages= has been added, that allows
mounting additional disk images into the file system tree accessible
to the service.
* systemd-repart now optionally outputs what it does in JSON format,
using the new --json= switch.
* systemd-machined's OpenMachineShell() bus call will now pass
additional policy metadata data fields to the PolicyKit
authentication request.
* systemd-tmpfiles gained a new -E switch, which is equivalent to
--exclude-prefix=/dev --exclude-prefix=/proc --exclude=/run
--exclude=/sys. It's particularly useful in combination with --root=,
when operating on OS trees that do not have any of these four runtime
directories mounted, as this means no files below these subtrees are
created or modified, since those mount points should probably remain
empty.
* systemd-tmpfiles gained a new --image= switch which is like --root=
but takes a disk image instead of a directory as argument. If
specified the disk image is mounted (inside a temporary mount
namespace) and the tmpfiles.d/ drop-ins stored in the image executed
and applied to the image. Similar, systemd-sysusers gained a new
--image= switch, that allows applying the sysusers.d/ drop-ins stored
in the image onto the image.
* Similar, the journalctl command also gained an --image= switch, which
is a quick one-step solution to look at the log data included in OS
disk images.
* journalctl's --output=cat option (which outputs the log content
without any metadata, just the pure text messages) will now make use
of terminal colors when run on a suitable terminal, similar to the
other output modes.
* JSON group records now support a "description" string that may be
used to add a human-readable textual description to such groups. This
is supposed to match the user's GECOS field which traditionally
didn't have a counterpart for group records.
* The "systemd-dissect" tool that may be used to inspect OS disk images
and that was previously installed to /usr/lib/systemd/ has now been
moved to /usr/bin/, reflecting that it's now considered an officially
supported tool with a stable interface. It gained support for a new
--mkdir switch which when combined with --mount has the effect of
creating the directory to mount the image to if it is missing
first. It also gained two new commands --copy-from and --copy-to for
copying files and directories in and out of an OS image without the
need to manually mount it. It also acquired support for a new option
--json= which controls whether to generate JSON output when
inspecting an OS image.
* The cgroup2 file system is now mounted with the
"memory_recursiveprot" mount option, supported since kernel 5.7. This
means that the MemoryLow= and MemoryMin= unit file settings now apply
recursively to whole subtrees.
* systemd-homed now defaults to using the btrfs file system — if
available — when creating home directories in LUKS volumes. This may
be changed with the DefaultFileSystemType= setting in
homed.conf. It's now the default file system in various major
distributions and has the major benefit for homed that it can be both
grown and shrunk while mounted, unlike the other contenders ext4 and
xfs, which can both be grown online, but not shrunk (in fact xfs is
the technically most limited option here, as it cannot be shrunk at
all).
* JSON user records managed by systemd-homed gained support for
"recovery keys". These are basically secondary passphrases that can
unlock user accounts/home directories, which are computer-generated
rather than user-chosen, and typically have greater
entropy. homectl's --recovery-key= option may be used to add a
recovery key to a user account. The generated recovery key is
displayed as QR code, so that it can be scanned off screen to be kept
at a safe place. This concept is particularly useful in combination
with systemd-homed's support for FIDO2 or PKCS#11 authentication, as
a secure fallback in case the security tokens are lost. Recovery keys
may be entered wherever the system asks for a password.
* systemd-homed now maintains a "dirty" flag for each LUKS encrypted
home directory that indicates whether a home directory has been
deactivated cleanly when offline. This flag is useful to identify
home directories for which the offline discard logic did not run when
offlining, and where it would be a good idea to log in again to catch
up.
* systemctl gained a new parameter --timestamp= which may be used to
change the style in which timestamps are output, i.e. whether to show
them in local timezone or UTC, or whether to show µs granularity.
* Alibaba's "pouch" container manager is now detected by
systemd-detect-virt, ConditionVirtualization= and similar constructs.
* systemd-nspawn has been reworked to use the /run/host/incoming/ as
place to use for propagating external mounts into the
container. Similar /run/host/notify is now used as socket path for
container payloads to communicate with the container manager using
sd_notify(). In the /run/host/inaccessible/ directory the container
manager now places "inaccessible" file nodes of all relevant types
which may be used by the container payload as bind mount source to
over-mount inodes that shall be made inaccessible
with. /run/host/container-manager will now be initialized to the same
string that the $container environment variable passed to the
container's PID 1 contains. /run/host/container-uuid will be
initialized to the same string $container_uuid is set to. This means
the /run/host/ hierarchy is now the primary way how host resources
are made available to containers. The Container Interface documents
these new files and directories:
https://systemd.io/CONTAINER_INTERFACE
* Support for the "ConditionNull=" unit file condition has been
removed. It has been deprecated and undocumented for 6 years
now. systemd started to warn about its use 1.5 years ago. It has now
been removed entirely.
* If the $SYSTEMD_LOG_SECCOMP=1 environment variable is set for
systemd-nspawn all system call filter collisions will be logged by
the kernel (audit). This is useful for tracking down system calls
invoked by container payloads that are prohibited by the container's
system call filter policy.
* sd-bus.h gained a new API call sd_bus_error_has_names(), which takes
a sd_bus_error struct and a list of error names, and checks if the
error matches one of these names. It's a convenience wrapper that is
useful in cases where multiple errors shall be handled the same way.
* A new system call filter list "@known" has been added, that contains
all system calls known at build-time of systemd.
* Behaviour of system call filter allow lists has changed slightly:
system calls that are contained in @known will result in a EPERM by
default, while those not contained in it result in ENOSYS. This
should improve compatibility because known syscalls will thus be
communicated as prohibited, while unknown (and thus newer ones) will
be communicated as not implemented, which hopefully has the greatest
chance of triggering the right fallback code paths in client
applications.
* Two new unit file settings ProtectProc= and ProcSubset= have been
added that expose the hidepid= and subset= mount options of
procfs. When used on services all processes inside it will only see
processes in /proc that are are owned by the service's user
themselves. This is an important new sandboxing option that is
recommended to be set on all system services where that's
possible. All long-running system services that are included in
systemd itself set this option now. This option is only supported on
kernel 5.8 and above, since the hidepid= option supported on older
kernels was not a per-mount option but actually applied to the whole
PID namespace.
* Socket units gained a new boolean setting FlushPending=. If enabled
all pending socket data/connections are flushed whenever the socket
unit enters the "listening" state, i.e. after the associated service
exited.
* The unit file setting NUMAMask= gained a new "all" value: if set, all
existing NUMA nodes are added to the NUMA mask.
* A new "credentials" logic has been added to system services. This is
a simple mechanism to pass privileged data to services in a safe and
secure way. It's supposed to be used to pass per-service secret data
such as passwords or cryptographic keys but also associated less
private information such as user names, certificates, and similar to
system services. Each credential is identified by a short user-chosen
name and may contain arbitrary binary data. Two new unit file
settings have been added for this: SetCredential= and
LoadCredential=. The former allows setting a credential to a literal
string, the latter sets a credential to the contents of a file (or
data read from a user-chosen AF_UNIX stream socket). Credentials are
passed to the service via a special credentials directory whose path
is passed in the new $CREDENTIALS_DIRECTORY environment variable,
which contains one file for each credential. Since the credentials
are passed in the file system they may be easily referenced in
ExecStart= command lines too, thus not requiring any explicit support
for the credentials logic in daemons (though ideally daemons would
look for the bits they need in $CREDENTIALS_DIRECTORY themselves
automatically, if set). The $CREDENTIALS_DIRECTORY is backed by
unswappable memory (if privileges allow it), is immutable (also if
privileges allow it), is accessible only to the service's UID, and is
automatically destroyed when the service goes down.
* systemd-nspawn supports the same credentials logic. It can both
consume credentials passed to it via the aforementioned
$CREDENTIALS_DIRECTORY protocol as well as pass these credentials on
to its payload. The service manager/PID 1 has been updated to match
this: it can also accept credentials from the container manager that
invokes it (in fact: any process that invokes it), and pass it on to
its services. Thus, credentials can be propagated fully down the
tree: from a system's service manager to a systemd-nspawn service, to
the service manager tat runs as container payload and to the service
it runs below. Credentials may also be added on the systemd-nspawn
command line, using the new --set-credential= and --load-credential=
command line switches, that match the aforementioned service
settings.
* systemd-repart gained new settings Format=, Encrypt=, CopyFiles= in
the partition drop-ins which may be used to format/LUKS
encrypt/populate any created partitions. The partitions are
encrypted/formatted/populated before they are registered in the
partition table, so that they appear "atomically": either the
partitions do not exist yet or they exist fully
encrypted/formatted/populated — there is no time window where they
are "half-initialized". Thus the system is robust to abrupt shutdown:
if the tool is terminated half-way during its operations on next boot
it will start from the beginning.
* systemd-repart's --size= operation gained a new "auto" value. If
specified, and operating on a loopback file it is automatically sized
to the minimal size the size constraints permit. This is useful to
use "systemd-repart" as an image builder for minimally sized images.
* systemd-resolved now supports a third IPC interface for requesting
name resolution: besides D-Bus and local DNS to 127.0.0.53 a Varlink
interface is now supported. The nss-resolve NSS modules has been
modified to use this new interface instead of D-Bus now. Using
Varlink has a major benefit over D-Bus: it works without a broker
service, and thus already during earliest boot, before dbus-daemon is
invoked (which is a late boot service). This means name resolution
via systemd-resolved now works at the same time systemd-networkd
operates: from earliest boot on, including in the initrd.
* systemd-resolved gained support for a new DNSStubListenerExtra=
configuration file setting which may be used to specify additional IP
addresses the built-in DNS stub shall listen on, in addition to the
main one on 127.0.0.53:53.
* Name lookups issued via systemd-resolved's D-Bus and Varlink
interfaces (and thus also via glibc NSS if nss-resolve is used) will
now honour a trailing dot in the hostname: if specified the search
path logic is turned off. Thus "resolvectl query foo.bar." is now
equivalent to "resolvectl query --search=off foo.bar".
* systemd-resolved gained a new D-Bus property "ResolvConfMode" that
exposes how /etc/resolv.conf is currently managed: by resolved (and
in which mode if so) or another subsystem. "resolvctl" will display
this property in its status output.
* The resolv.conf snippets systemd-resolved provides will now set "."
as search domain if no other search domain is known. This turns off
behaviour in glibc that an implicit search domain is derived from the
local system's hostname if it is set to an FQDN.
* systemd-tmpfiles' file "aging" logic (i.e. the automatic clean-up of
/tmp/ and /var/tmp/ based on file timestamps) now looks at the
"birth" time (btime) of a file in addition to the atime, mtime,
ctime, to determine if it should be kept or deleted.
* systemd-analyze gained a new verb "capability" that lists all known
capabilities by the systemd build and by the kernel.
* If a file /usr/lib/clock-epoch exists, PID 1 will read its mtime and
advance the system clock to it at boot if it is noticed to be before
that time. Previously, PID 1 would only advance the time to an epoch
time that is set during build-time. With this new file OS builders
can change this epoch timestamp on individual OS images without
having to rebuild systemd.
* systemd-logind will now listen to the KEY_RESTART key from the Linux
input layer and reboot the system if it is pressed, similar to how it
already handles KEY_POWER, KEY_SUSPEND or KEY_SLEEP. KEY_RESTART was
originally defined in a Multimedia context (to restart playback of a
song or film), but is now primarily used in various embedded devices
for "Reboot" buttons. Accordingly, systemd-logind will now honour it
as such. This may configured in more detail via the new
HandleRebootKey= and RebootKeyIgnoreInhibited=.
* systemd-nspawn/systemd-machined will now reconstruct hardlinks when
copying OS trees, for example in "systemd-nspawn --ephemeral",
"systemd-nspawn --template=", "machinectl clone" and similar. This is
useful when operating with OSTree images, which use hardlinks heavily
throughout, and where such copies previously resulting in "exploding"
hardlinks.
* systemd-nspawn's --console= setting gained support for a new
"autopipe" value, which is identical to "interactive" when invoked on
a TTY, and "pipe" otherwise.
* systemd-networkd's .network files gained support for explicitly
configuring the multicast membership entries of bridge devices in the
[BridgeMDB] section. It also gained support for the PIE queuing
discipline in the [FlowQueuePIE] sections.
* systemd-networkd's .netdev files may now be used to create "BareUDP"
tunnels, configured in the new [BareUDP] setting. VXLAN tunnels may
now be marked to be independent of any underlying network interface
via the new Independent= boolean setting.
* systemctl gained support for two new verbs: "log-level" and
"log-target" which may be used on services that implement the generic
org.freedesktop.LogControl1 D-Bus interface for dynamically adjusting
the log level and target. All of systemd's long-running services
support this now, but ideally any system service would implement this
interface to make the system more uniformly inspectable and
debuggable.
* The SystemCallErrorNumber= unit file setting now accepts the new
"kill" and "log" actions, in addition to arbitrary error number
specifications as before. If "kill" the the processes are killed on
the event, if "log" the offending syscall is audit logged.
* A new SystemCallLog= unit file setting has been added that accepts a
list of syscalls that shall be logged about (audit).
* The OS image dissection logic (as used by RootImage= in unit files or
systemd-nspawn's --image= switch) has learnt support for identifying
and mounting explicit /usr/ partitions, which are now defined in the
discoverable partition specification. This should be useful for
environments where the root file system is
generated/formatted/populated dynamically on first boot and combined
with an immutable /usr/ tree that is supplied by the vendor.
* In the final phase of shutdown, within the systemd-shutdown binary
we'll now try to detach MD devices (i.e software RAID) in addition to
loopback block devices and DM devices as before. This is supposed to
be a safety net only, in order to increase robustness if things go
wrong. Storage subsystems are expected to properly detach their
storage volumes during regular shutdown already (or in case of
storage backing the root file system: in the initrd hook we return to
later).
* If the SYSTEMD_LOG_TID environment variable is set all systemd tools
will now log the thread ID in their log output. This is useful when
working with heavily threaded programs.
* If the SYSTEMD_RDRAND enviroment variable is set to "0" systemd's use
of the RDRAND CPU instruction is disabled. This is useful in
environments such as replay debuggers where CPU level
non-deterministic behaviour is not desirable.
* When building systemd the Meson option
"compat-mutable-uid-boundaries" may now be specified. If so systemd
reads the system UID boundaries from /etc/login.defs, instead of using
the built-in values selected during build-time. This is an option to
improve compatibility for upgrades from old systems. It's strongly
recommended not to make use of this functionality on new systems (or
even enable it during build), as it makes something
runtime-configurable that is mostly an implementation detail of the
OS, and permits avoidable differences in deployments that create all
kinds of problems in the long run.
CHANGES WITH 246:
* The service manager gained basic support for cgroup v2 freezer. Units