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systemd/README
Martin Pitt 1d40ddbfd3 core: drop check for /etc/mtab 
util-linux 2.27.1 now entirely stops looking at /etc/mtab, so we don't need to
verify /etc/mtab during early boot any more. Later on, tmpfiles.d/etc.conf will
fix /etc/mtab anyway, so there's not even a point in warning about it.

Drop test_mtab() and bump the util-linux dependency to >= 2.17.1.

Fixes #1495
2015-11-02 10:05:20 -06:00

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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
http://lists.freedesktop.org/mailman/listinfo/systemd-commits
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 >= 3.11
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_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 systemd-bootchart, several proc debug interfaces are required:
CONFIG_SCHEDSTATS
CONFIG_SCHED_DEBUG
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)
libseccomp >= 1.0.0 (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 kdbus dbus1 proxy daemon requires the
"systemd-bus-proxy" system user and group to exist.
NSS:
systemd ships with three 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.
To make use of these NSS modules, please add them to the
"hosts: " line in /etc/nsswitch.conf. The "resolve" module
should replace the glibc "dns" module in this file.
The three modules should be used in the following order:
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 freeze execution during boot if /etc/mtab exists
but is not a symlink to /proc/mounts. Please ensure that
/etc/mtab is a proper symlink.
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.
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