After five months of development the release of the new version of systemd 251 was announced, version in which the system requirements were increased. The minimum supported version of the Linux kernel has been increased from 3.13 to 4.15. Requires the CLOCK_BOOTTIME timer to work. To compile, you need a compiler that supports the C11 standard and GNU extensions (the C89 standard is still used for header files).
For the part of the novelties that stand out from this new version, it is highlighted that se added an experimental utility systemd-sysupdate for automatically detect, download and install updates using the atomic mechanism to replace partitions, files or directories.
Another change that stands out is that a new internal shared library is introduced, libsystemd-core- .so, which is installed in the /usr/lib/systemd/system directory and corresponds to the libsystemd-shared-library .so existing. Using the shared library libsystemd-core- .SW reduces the overall size of the installation by reusing the binary code. The version number can be specified via the 'shared-lib-tag' option in the meson build system and allows distributions to ship multiple versions of these libraries at the same time.
In addition to this, it is also highlighted that environment variable passing has been implemented $MONITOR_SERVICE_RESULT, $MONITOR_EXIT_CODE, $MONITOR_EXIT_STATUS, $MONITOR_INVOCATION_ID and $MONITOR_UNIT that contain information about the monitored unit to the OnFailure/OnSuccess controllers.
For units, the ExtensionDirectories setting is implemented, which can be used to organize the loading of System Extension components from regular directories, rather than disk images. The contents of the system expansion directory overlays OverlayFS and is used to expand the /usr/ and /opt/ directory hierarchy and add additional files at runtime, even if the specified directories are mounted read-only. Support for specifying a directory has also been added to the 'portablectl added –extension=' command.
En systemd-networkd, for unicast routes configured via the [Route] section, the scope value was changed from default to "link" to match the behavior of the "ip route" command. Added “Isolated=true|false” parameter to [Bridge] section to configure the network bridges attribute of the same name in the kernel. In the [Tunnel] section, the External parameter has been added to configure a tunnel of external type (metadata collection mode).
Of the other changes that stand out:
- Added BootServerName, BootServerAddress, and BootFilename parameters to the [DHCPServer] section to configure the server address, server name, and boot file name sent by the DHCP server when booting in PXE mode.
- In the [Network] section, the L2TP parameter has been removed, instead of which in the .netdev files you can use the new Local settings regarding the L2TP interface.
- Ensured that systemd-resolved is started earlier in the boot process, including booting from initrd when systemd-resolved is present in the initrd image.
- Added –fido2-credential-algorithm option to systemd-cryptenroll to select the credential encryption algorithm and –tpm2-with-pin option to control PIN entry when unlocking a partition using TPM.
- Added a similar option tpm2-pin to /etc/crypttab. When unlocking devices through the TPM, the settings are encrypted to protect against interception of encryption keys.
- Added D-Bus API to systemd-timesyncd to dynamically retrieve information from an NTP server via IPC.
- To determine the need for color output on all commands, the COLORTERM environment variable is checked in addition to NO_COLOR, SYSTEMD_COLORS, and TERM, which were previously checked.
- The Meson build system implements the install_tag option for custom builds and installation of necessary components: pam, nss, devel (pkg-config), systemd-boot, libsystemd, libudev.
- Added default-compression build option to select compression algorithm for systemd-journald and systemd-coredump.
- Added experimental setting "reboot-for-bitlocker" to sd-boot in loader.conf to boot Microsoft Windows with BitLocker TPM.
- Systemd-journald has stabilized the ability to export in JSON format. Added support for JSON output in the “journalctl –list-boots” and “bootctl list” commands (“–json” flag).
- Added new hwdb database files to udev, which contain information about portable devices (PDAs, calculators, etc.) and devices used to create sound and video (DJ consoles, keyboards).
- The LoadCredential setting allows a directory name as an argument, in which case it attempts to load credentials from all files in the specified directory.
- In systemctl, the "--timestamp" parameter added the ability to specify the "unix" flag to display the time in epoch format (the number of seconds since January 1, 1970).
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