mirror of
https://github.com/systemd/systemd
synced 2024-09-06 16:56:43 +00:00
![Alan Jenkins](/assets/img/avatar_default.png)
`newinstance` (and `ptmxmode`) options of devpts are _not_ used by
PrivateDevices=. (/dev/pts is shared, similar to how /dev/shm and
/dev/mqueue are handled). It is used by nspawn containers though.
Also CONFIG_DEVPTS_MULTIPLE_INSTANCES was removed in 4.7-rc2
eedf265aa0
and no longer needs to be set, so make that clearer to avoid confusion.
321 lines
13 KiB
Plaintext
321 lines
13 KiB
Plaintext
systemd System and Service Manager
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DETAILS:
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http://0pointer.de/blog/projects/systemd.html
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WEB SITE:
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https://www.freedesktop.org/wiki/Software/systemd
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GIT:
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git@github.com:systemd/systemd.git
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https://github.com/systemd/systemd
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MAILING LIST:
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https://lists.freedesktop.org/mailman/listinfo/systemd-devel
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IRC:
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#systemd on irc.freenode.org
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BUG REPORTS:
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https://github.com/systemd/systemd/issues
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AUTHOR:
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Lennart Poettering
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Kay Sievers
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...and many others
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LICENSE:
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LGPLv2.1+ for all code
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- except src/basic/MurmurHash2.c which is Public Domain
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- except src/basic/siphash24.c which is CC0 Public Domain
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- except src/journal/lookup3.c which is Public Domain
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- except src/udev/* which is (currently still) GPLv2, GPLv2+
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REQUIREMENTS:
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Linux kernel >= 3.13
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Linux kernel >= 4.2 for unified cgroup hierarchy support
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Kernel Config Options:
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CONFIG_DEVTMPFS
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CONFIG_CGROUPS (it is OK to disable all controllers)
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CONFIG_INOTIFY_USER
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CONFIG_SIGNALFD
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CONFIG_TIMERFD
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CONFIG_EPOLL
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CONFIG_NET
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CONFIG_SYSFS
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CONFIG_PROC_FS
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CONFIG_FHANDLE (libudev, mount and bind mount handling)
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Kernel crypto/hash API
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CONFIG_CRYPTO_USER_API_HASH
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CONFIG_CRYPTO_HMAC
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CONFIG_CRYPTO_SHA256
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udev will fail to work with the legacy sysfs layout:
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CONFIG_SYSFS_DEPRECATED=n
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Legacy hotplug slows down the system and confuses udev:
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CONFIG_UEVENT_HELPER_PATH=""
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Userspace firmware loading is not supported and should
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be disabled in the kernel:
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CONFIG_FW_LOADER_USER_HELPER=n
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Some udev rules and virtualization detection relies on it:
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CONFIG_DMIID
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Support for some SCSI devices serial number retrieval, to
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create additional symlinks in /dev/disk/ and /dev/tape:
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CONFIG_BLK_DEV_BSG
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Required for PrivateNetwork= in service units:
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CONFIG_NET_NS
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Note that systemd-localed.service and other systemd units use
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PrivateNetwork so this is effectively required.
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Required for PrivateUsers= in service units:
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CONFIG_USER_NS
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Optional but strongly recommended:
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CONFIG_IPV6
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CONFIG_AUTOFS4_FS
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CONFIG_TMPFS_XATTR
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CONFIG_{TMPFS,EXT4_FS,XFS,BTRFS_FS,...}_POSIX_ACL
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CONFIG_SECCOMP
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CONFIG_SECCOMP_FILTER (required for seccomp support)
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CONFIG_CHECKPOINT_RESTORE (for the kcmp() syscall)
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Required for CPUShares= in resource control unit settings
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CONFIG_CGROUP_SCHED
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CONFIG_FAIR_GROUP_SCHED
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Required for CPUQuota= in resource control unit settings
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CONFIG_CFS_BANDWIDTH
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Required for IPAddressDeny= and IPAddressAllow= in resource control
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unit settings
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CONFIG_CGROUP_BPF
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For UEFI systems:
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CONFIG_EFIVAR_FS
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CONFIG_EFI_PARTITION
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We recommend to turn off Real-Time group scheduling in the
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kernel when using systemd. RT group scheduling effectively
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makes RT scheduling unavailable for most userspace, since it
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requires explicit assignment of RT budgets to each unit whose
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processes making use of RT. As there's no sensible way to
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assign these budgets automatically this cannot really be
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fixed, and it's best to disable group scheduling hence.
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CONFIG_RT_GROUP_SCHED=n
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It's a good idea to disable the implicit creation of networking bonding
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devices by the kernel networking bonding module, so that the
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automatically created "bond0" interface doesn't conflict with any such
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device created by systemd-networkd (or other tools). Ideally there
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would be a kernel compile-time option for this, but there currently
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isn't. The next best thing is to make this change through a modprobe.d
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drop-in. This is shipped by default, see modprobe.d/systemd.conf.
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Required for systemd-nspawn:
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CONFIG_DEVPTS_MULTIPLE_INSTANCES or Linux kernel >= 4.7
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Note that kernel auditing is broken when used with systemd's
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container code. When using systemd in conjunction with
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containers, please make sure to either turn off auditing at
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runtime using the kernel command line option "audit=0", or
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turn it off at kernel compile time using:
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CONFIG_AUDIT=n
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If systemd is compiled with libseccomp support on
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architectures which do not use socketcall() and where seccomp
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is supported (this effectively means x86-64 and ARM, but
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excludes 32-bit x86!), then nspawn will now install a
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work-around seccomp filter that makes containers boot even
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with audit being enabled. This works correctly only on kernels
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3.14 and newer though. TL;DR: turn audit off, still.
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glibc >= 2.16
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libcap
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libmount >= 2.30 (from util-linux)
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(util-linux *must* be built without --enable-libmount-support-mtab)
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libseccomp >= 2.3.1 (optional)
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libblkid >= 2.24 (from util-linux) (optional)
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libkmod >= 15 (optional)
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PAM >= 1.1.2 (optional)
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libcryptsetup (optional)
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libaudit (optional)
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libacl (optional)
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libselinux (optional)
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liblzma (optional)
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liblz4 >= 119 (optional)
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libgcrypt (optional)
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libqrencode (optional)
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libmicrohttpd (optional)
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libpython (optional)
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libidn2 or libidn (optional)
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elfutils >= 158 (optional)
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polkit (optional)
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pkg-config
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gperf
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docbook-xsl (optional, required for documentation)
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xsltproc (optional, required for documentation)
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python-lxml (optional, required to build the indices)
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python, meson, ninja
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gcc, awk, sed, grep, m4, and similar tools
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During runtime, you need the following additional
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dependencies:
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util-linux >= v2.27.1 required
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dbus >= 1.4.0 (strictly speaking optional, but recommended)
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NOTE: If using dbus < 1.9.18, you should override the default
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policy directory (--with-dbuspolicydir=/etc/dbus-1/system.d).
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dracut (optional)
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PolicyKit (optional)
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To build in directory build/:
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meson build/ && ninja -C build
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Any configuration options can be specfied as -Darg=value... arguments
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to meson. After the build directory is initially configured, meson will
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refuse to run again, and options must be changed with:
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mesonconf -Darg=value...
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mesonconf without any arguments will print out available options and
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their current values.
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Useful commands:
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ninja -v some/target
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ninja test
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sudo ninja install
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DESTDIR=... ninja install
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A tarball can be created with:
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git archive --format=tar --prefix=systemd-222/ v222 | xz > systemd-222.tar.xz
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When systemd-hostnamed is used, it is strongly recommended to
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install nss-myhostname to ensure that, in a world of
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dynamically changing hostnames, the hostname stays resolvable
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under all circumstances. In fact, systemd-hostnamed will warn
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if nss-myhostname is not installed.
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nss-systemd must be enabled on systemd systems, as that's required for
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DynamicUser= to work. Note that we ship services out-of-the-box that
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make use of DynamicUser= now, hence enabling nss-systemd is not
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optional.
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Note that the build prefix for systemd must be /usr. -Dsplit-usr=false
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(which is the default and does not need to be specified) is the
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recommended setting, and -Dsplit-usr=true should be used on systems
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which have /usr on a separate partition.
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Additional packages are necessary to run some tests:
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- busybox (used by test/TEST-13-NSPAWN-SMOKE)
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- nc (used by test/TEST-12-ISSUE-3171)
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- python3-pyparsing
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- python3-evdev (used by hwdb parsing tests)
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- strace (used by test/test-functions)
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- capsh (optional, used by test-execute)
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USERS AND GROUPS:
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Default udev rules use the following standard system group
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names, which need to be resolvable by getgrnam() at any time,
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even in the very early boot stages, where no other databases
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and network are available:
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audio, cdrom, dialout, disk, input, kmem, kvm, lp, render, tape, tty, video
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During runtime, the journal daemon requires the
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"systemd-journal" system group to exist. New journal files will
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be readable by this group (but not writable), which may be used
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to grant specific users read access. In addition, system
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groups "wheel" and "adm" will be given read-only access to
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journal files using systemd-tmpfiles.service.
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The journal gateway daemon requires the
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"systemd-journal-gateway" system user and group to
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exist. During execution this network facing service will drop
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privileges and assume this uid/gid for security reasons.
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Similarly, the NTP daemon requires the "systemd-timesync" system
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user and group to exist.
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Similarly, the network management daemon requires the
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"systemd-network" system user and group to exist.
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Similarly, the name resolution daemon requires the
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"systemd-resolve" system user and group to exist.
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Similarly, the coredump support requires the
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"systemd-coredump" system user and group to exist.
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NSS:
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systemd ships with four glibc NSS modules:
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nss-myhostname resolves the local hostname to locally
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configured IP addresses, as well as "localhost" to
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127.0.0.1/::1.
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nss-resolve enables DNS resolution via the systemd-resolved
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DNS/LLMNR caching stub resolver "systemd-resolved".
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nss-mymachines enables resolution of all local containers registered
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with machined to their respective IP addresses. It also maps UID/GIDs
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ranges used by containers to useful names.
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nss-systemd enables resolution of all dynamically allocated service
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users. (See the DynamicUser= setting in unit files.)
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To make use of these NSS modules, please add them to the "hosts:",
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"passwd:" and "group:" lines in /etc/nsswitch.conf. The "resolve"
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module should replace the glibc "dns" module in this file (and don't
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worry, it chain-loads the "dns" module if it can't talk to resolved).
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The four modules should be used in the following order:
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passwd: compat mymachines systemd
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group: compat mymachines systemd
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hosts: files mymachines resolve myhostname
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SYSV INIT.D SCRIPTS:
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When calling "systemctl enable/disable/is-enabled" on a unit which is a
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SysV init.d script, it calls /usr/lib/systemd/systemd-sysv-install;
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this needs to translate the action into the distribution specific
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mechanism such as chkconfig or update-rc.d. Packagers need to provide
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this script if you need this functionality (you don't if you disabled
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SysV init support).
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Please see src/systemctl/systemd-sysv-install.SKELETON for how this
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needs to look like, and provide an implementation at the marked places.
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WARNINGS:
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systemd will warn during early boot if /usr is not already mounted at
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this point (that means: either located on the same file system as / or
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already mounted in the initrd). While in systemd itself very little
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will break if /usr is on a separate, late-mounted partition, many of
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its dependencies very likely will break sooner or later in one form or
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another. For example, udev rules tend to refer to binaries in /usr,
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binaries that link to libraries in /usr or binaries that refer to data
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files in /usr. Since these breakages are not always directly visible,
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systemd will warn about this, since this kind of file system setup is
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not really supported anymore by the basic set of Linux OS components.
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systemd requires that the /run mount point exists. systemd also
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requires that /var/run is a symlink to /run.
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For more information on this issue consult
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https://www.freedesktop.org/wiki/Software/systemd/separate-usr-is-broken
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To run systemd under valgrind, compile with VALGRIND defined
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(e.g. CPPFLAGS='... -DVALGRIND=1' meson <options>) and have valgrind
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development headers installed (i.e. valgrind-devel or
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equivalent). Otherwise, false positives will be triggered by code which
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violates some rules but is actually safe. Note that valgrind generates
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nice output only on exit(), hence on shutdown we don't execve()
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systemd-shutdown.
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ENGINEERING AND CONSULTING SERVICES:
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Kinvolk (https://kinvolk.io) offers professional engineering
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and consulting services for systemd. Please contact Chris Kühl
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<chris@kinvolk.io> for more information.
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