systemd System and Service Manager DETAILS: http://0pointer.de/blog/projects/systemd.html WEB SITE: http://www.freedesktop.org/wiki/Software/systemd GIT: git@github.com:systemd/systemd.git https://github.com/systemd/systemd.git GITWEB: https://github.com/systemd/systemd MAILING LIST: http://lists.freedesktop.org/mailman/listinfo/systemd-devel IRC: #systemd on irc.freenode.org BUG REPORTS: https://github.com/systemd/systemd/issues AUTHOR: Lennart Poettering Kay Sievers ...and many others LICENSE: LGPLv2.1+ for all code - except src/basic/MurmurHash2.c which is Public Domain - except src/basic/siphash24.c which is CC0 Public Domain - except src/journal/lookup3.c which is Public Domain - except src/udev/* which is (currently still) GPLv2, GPLv2+ REQUIREMENTS: Linux kernel >= 3.12 Linux kernel >= 4.2 for unified cgroup hierarchy support Kernel Config Options: CONFIG_DEVTMPFS CONFIG_CGROUPS (it is OK to disable all controllers) CONFIG_INOTIFY_USER CONFIG_SIGNALFD CONFIG_TIMERFD CONFIG_EPOLL CONFIG_NET CONFIG_SYSFS CONFIG_PROC_FS CONFIG_FHANDLE (libudev, mount and bind mount handling) udev will fail to work with the legacy sysfs layout: CONFIG_SYSFS_DEPRECATED=n Legacy hotplug slows down the system and confuses udev: CONFIG_UEVENT_HELPER_PATH="" Userspace firmware loading is not supported and should be disabled in the kernel: CONFIG_FW_LOADER_USER_HELPER=n Some udev rules and virtualization detection relies on it: CONFIG_DMIID Support for some SCSI devices serial number retrieval, to create additional symlinks in /dev/disk/ and /dev/tape: CONFIG_BLK_DEV_BSG Required for PrivateNetwork and PrivateDevices in service units: CONFIG_NET_NS CONFIG_DEVPTS_MULTIPLE_INSTANCES Note that systemd-localed.service and other systemd units use PrivateNetwork and PrivateDevices so this is effectively required. Optional but strongly recommended: CONFIG_IPV6 CONFIG_AUTOFS4_FS CONFIG_TMPFS_XATTR CONFIG_{TMPFS,EXT4,XFS,BTRFS_FS,...}_POSIX_ACL CONFIG_SECCOMP CONFIG_SECCOMP_FILTER (required for seccomp support) CONFIG_CHECKPOINT_RESTORE (for the kcmp() syscall) Required for CPUShares= in resource control unit settings CONFIG_CGROUP_SCHED CONFIG_FAIR_GROUP_SCHED Required for CPUQuota= in resource control unit settings CONFIG_CFS_BANDWIDTH For UEFI systems: CONFIG_EFIVAR_FS CONFIG_EFI_PARTITION We recommend to turn off Real-Time group scheduling in the kernel when using systemd. RT group scheduling effectively makes RT scheduling unavailable for most userspace, since it requires explicit assignment of RT budgets to each unit whose processes making use of RT. As there's no sensible way to assign these budgets automatically this cannot really be fixed, and it's best to disable group scheduling hence. CONFIG_RT_GROUP_SCHED=n Note that kernel auditing is broken when used with systemd's container code. When using systemd in conjunction with containers, please make sure to either turn off auditing at runtime using the kernel command line option "audit=0", or turn it off at kernel compile time using: CONFIG_AUDIT=n If systemd is compiled with libseccomp support on architectures which do not use socketcall() and where seccomp is supported (this effectively means x86-64 and ARM, but excludes 32-bit x86!), then nspawn will now install a work-around seccomp filter that makes containers boot even with audit being enabled. This works correctly only on kernels 3.14 and newer though. TL;DR: turn audit off, still. glibc >= 2.16 libcap libmount >= 2.27.1 (from util-linux) (util-linux *must* be built with --enable-libmount-force-mountinfo) libseccomp >= 2.3.1 (optional) libblkid >= 2.24 (from util-linux) (optional) libkmod >= 15 (optional) PAM >= 1.1.2 (optional) libcryptsetup (optional) libaudit (optional) libacl (optional) libselinux (optional) liblzma (optional) liblz4 >= 119 (optional) libgcrypt (optional) libqrencode (optional) libmicrohttpd (optional) libpython (optional) libidn (optional) elfutils >= 158 (optional) make, gcc, and similar tools During runtime, you need the following additional dependencies: util-linux >= v2.27.1 required dbus >= 1.4.0 (strictly speaking optional, but recommended) dracut (optional) PolicyKit (optional) When building from git, the following tools are needed: pkg-config docbook-xsl xsltproc automake autoconf libtool intltool gperf python (optional) python-lxml (optional, but required to build the indices) The build system is initialized with ./autogen.sh. A tar ball can be created with: git archive --format=tar --prefix=systemd-222/ v222 | xz > systemd-222.tar.xz When systemd-hostnamed is used, it is strongly recommended to install nss-myhostname to ensure that, in a world of dynamically changing hostnames, the hostname stays resolvable under all circumstances. In fact, systemd-hostnamed will warn if nss-myhostname is not installed. USERS AND GROUPS: Default udev rules use the following standard system group names, which need to be resolvable by getgrnam() at any time, even in the very early boot stages, where no other databases and network are available: audio, cdrom, dialout, disk, input, kmem, lp, tape, tty, video During runtime, the journal daemon requires the "systemd-journal" system group to exist. New journal files will be readable by this group (but not writable), which may be used to grant specific users read access. In addition, system groups "wheel" and "adm" will be given read-only access to journal files using systemd-tmpfiles.service. The journal gateway daemon requires the "systemd-journal-gateway" system user and group to exist. During execution this network facing service will drop privileges and assume this uid/gid for security reasons. Similarly, the NTP daemon requires the "systemd-timesync" system user and group to exist. Similarly, the network management daemon requires the "systemd-network" system user and group to exist. Similarly, the name resolution daemon requires the "systemd-resolve" system user and group to exist. Similarly, the coredump support requires the "systemd-coredump" system user and group to exist. NSS: systemd ships with four glibc NSS modules: nss-myhostname resolves the local hostname to locally configured IP addresses, as well as "localhost" to 127.0.0.1/::1. nss-resolve enables DNS resolution via the systemd-resolved DNS/LLMNR caching stub resolver "systemd-resolved". nss-mymachines enables resolution of all local containers registered with machined to their respective IP addresses. It also maps UID/GIDs ranges used by containers to useful names. nss-systemd enables resolution of all dynamically allocated service users. (See the DynamicUser= setting in unit files.) To make use of these NSS modules, please add them to the "hosts:", "passwd:" and "group:" lines in /etc/nsswitch.conf. The "resolve" module should replace the glibc "dns" module in this file (and don't worry, it chain-loads the "dns" module if it can't talk to resolved). The four modules should be used in the following order: passwd: compat mymachines systemd group: compat mymachines systemd hosts: files mymachines resolve myhostname SYSV INIT.D SCRIPTS: When calling "systemctl enable/disable/is-enabled" on a unit which is a SysV init.d script, it calls /usr/lib/systemd/systemd-sysv-install; this needs to translate the action into the distribution specific mechanism such as chkconfig or update-rc.d. Packagers need to provide this script if you need this functionality (you don't if you disabled SysV init support). Please see src/systemctl/systemd-sysv-install.SKELETON for how this needs to look like, and provide an implementation at the marked places. WARNINGS: systemd will warn you during boot if /usr is on a different file system than /. While in systemd itself very little will break if /usr is on a separate partition, many of its dependencies very likely will break sooner or later in one form or another. For example, udev rules tend to refer to binaries in /usr, binaries that link to libraries in /usr or binaries that refer to data files in /usr. Since these breakages are not always directly visible, systemd will warn about this, since this kind of file system setup is not really supported anymore by the basic set of Linux OS components. systemd requires that the /run mount point exists. systemd also requires that /var/run is a symlink to /run. For more information on this issue consult http://freedesktop.org/wiki/Software/systemd/separate-usr-is-broken To run systemd under valgrind, compile with VALGRIND defined (e.g. ./configure CPPFLAGS='... -DVALGRIND=1'). Otherwise, false positives will be triggered by code which violates some rules but is actually safe. Currently, systemd-timesyncd defaults to use the Google NTP servers if not specified otherwise at configure time. You really should not ship an OS or device with this default setting. See DISTRO_PORTING for details. ENGINEERING AND CONSULTING SERVICES: Kinvolk (https://kinvolk.io) offers professional engineering and consulting services for systemd. Please contact Chris Kühl <chris@kinvolk.io> for more information.