Systemd

• systemctl

• Units

• target

• Config

  • add

• debug

• journald

• systemd-networkd.service

• systemd.netdev

  • Kind

  • Examples

    • bridge.netdev

    • dummy.netdev

    • vlan1.netdev

    • macvtap.netdev

• systemd.network

  • static.network

  • dhcp.network

  • A bridge with two enslaved links

  • bridge-slave-interface-vlan.network

  • macvtap.network

• systemd.link

systemctl

https://wiki.archlinux.org/index.php/systemd

systemctl --all
systemctl list-dependencies
systemctl list-dependencies libvirtd --all

systemctl status [___.service]
systemctl | grep ssh
systemctl --failed
systemctl daemon-reload    # scanning for new or changed units

systemctl enable unit   # start on boot
systemctl mask unit     # make it impossible to start

sudo systemd-analyze plot > /tmp/systemd-startup.svg
fbi /tmp/systemd-startup.svg

Units

• .service: default

• [email protected]: instances of a template unit， actually '[email protected]

• .mount, E.g.: /home is equivalent to home.mount

• .device, E.g.: /dev/sda2 is equivalent to dev-sda2.device

• .socket

• .slice

More: https://www.freedesktop.org/software/systemd/man/systemd.unit.html

# when running in system mode (--system)
ls -l /run/systemd/system	    # Runtime units
ls -l /usr/lib/systemd/system	# Units of installed packages
ls -l /etc/systemd/system	    # Local configuration, by SA

target

https://wiki.archlinux.org/index.php/systemd#Create_custom_target

SysV Runlevel	systemd Target	                                        Notes
0	            runlevel0.target, poweroff.target	                    Halt the system.
1, s, single	runlevel1.target, rescue.target	                        Single user mode.
2, 4	        runlevel2.target, runlevel4.target, multi-user.target	User-defined/Site-specific runlevels. By default, identical to 3.
3	            runlevel3.target, multi-user.target	                    usually login via multiple consoles or network.
5	            runlevel5.target, graphical.target	                    Multi-user, graphical.
6	            runlevel6.target, reboot.target	                        Reboot
emergency	    emergency.target	                                    Emergency shell

systemctl isolate multi-user.target         # switch to target
systemctl get-default                       # current target
systemctl set-default multi-user.target

Config

http://fedoraproject.org/wiki/Systemd#How_do_I_customize_a_unit_file.2F_add_a_custom_unit_file.3F /etc/systemd/system/foobar.service.d/*.conf # override settings

systemctl cat unit
systemctl edit --full ssh
systemctl edit --force new

[Unit]
Description=new

[Service]
ExecStart=/usr/sbin/new-daemon

[Install]
WantedBy=multi-user.target

add

cp -pv foo.service /etc/systemd/system/
systemctl daemon-reload
systemctl enable foo
systemctl start foo
systemctl status foo

debug

https://wiki.debian.org/systemd#Debugging

/etc/systemd/system.conf
    LogLevel=debug
    LogTarget=syslog-or-kmsg

journald

# http://man7.org/linux/man-pages/man5/journald.conf.5.html
sudo mkdir -p /var/log/journal  # persistent storage

journalctl -u unit

SYSTEMD_LESS="FRXMK" journalctl -u docker -n 100
-S, --since=, -U, --until=

https://wiki.archlinux.org/index.php/systemd#Journal

systemd-networkd.service

/usr/lib/systemd/systemd-networkd https://wiki.archlinux.org/index.php/systemd-networkd https://www.freedesktop.org/software/systemd/man/systemd.netdev.html#

systemctl status systemd-networkd.service
systemctl restart systemd-networkd.service

# networkctl list
IDX LINK             TYPE               OPERATIONAL SETUP     
  1 lo               loopback           carrier     unmanaged 
  2 enp3s0           ether              no-carrier  unmanaged 
  3 eno1             ether              degraded    unmanaged 
  4 eno2             ether              degraded    configured
  7 docker0          ether              routable    unmanaged 
  9 vethec09cbe      ether              degraded    unmanaged 
 11 veth5185e04      ether              degraded    unmanaged 
 12 zt0              ether              routable    unmanaged 
 13 br0              ether              routable    configured
 14 macvtap0         ether              degraded    unmanaged 
 15 vnet0            ether              degraded    unmanaged 
 16 br8              ether              off         unmanaged 
 18 macvtap1         ether              degraded    unmanaged 
 19 vnet1            ether              degraded    unmanaged 

systemd.netdev

ls /etc/systemd/network     # local administration network directory
ls /usr/lib/systemd/network # system network directory
ls /run/systemd/network     # volatile runtime network directory
`/run` is temporary and `/usr/lib` is for vendors
symlink with the same name pointing to `/dev/null` disables the configuration file entirely

Kind

`bridge`	A bridge device is a software switch, and each of its slave devices and the bridge itself are ports of the switch.
`tap`	A persistent Level 2 tunnel between a network device and a device node.
`tun`	A persistent Level 3 tunnel between a network device and a device node.
`veth`	An Ethernet tunnel between a pair of network devices.
`sit`	An IPv6 over IPv4 tunnel.
`vti`	An IPv4 over IPSec tunnel.

Examples

bridge.netdev

[NetDev]
Name=bridge0
Kind=bridge

[Match]
Virtualization=no

dummy.netdev

[NetDev]
Name=dummy-test
Kind=dummy
MACAddress=12:34:56:78:9a:bc

vlan1.netdev

[NetDev]
Name=vlan1
Kind=vlan

[VLAN]
Id=1

macvtap.netdev

[NetDev]
Name=macvtap-test
Kind=macvtap

Compare with macvtap.network below.

systemd.network

https://www.freedesktop.org/software/systemd/man/systemd.network.html

static.network

[Match]
Name=enp2s0

[Network]
Address=192.168.0.15/24
Gateway=192.168.0.1

dhcp.network

[Match]
Name=en*

[Network]
DHCP=yes

A bridge with two enslaved links

# /etc/systemd/network/25-bridge-static.network
[Match]
Name=bridge0

[Network]
...

# /etc/systemd/network/25-bridge-slave-interface-1.network
[Match]
Name=enp2s0

[Network]
Bridge=bridge0

# /etc/systemd/network/25-bridge-slave-interface-x.network 

bridge-slave-interface-vlan.network

[Match]
Name=enp2s0

[Network]
Bridge=bridge0

[BridgeVLAN]
VLAN=1-32
PVID=42
EgressUntagged=42

[BridgeVLAN]
VLAN=100-200

[BridgeVLAN]
EgressUntagged=300-400

VLAN=
The VLAN ID allowed on the port. 

EgressUntagged=
The VLAN ID specified here will be used to untag frames on egress. 
Configuring EgressUntagged= implicates the use of VLAN= above and will enable the VLAN ID for ingress as well. 

PVID=
The Port VLAN ID specified here is assigned to all untagged frames at ingress. PVID= can be used only once. 
Configuring PVID= implicates the use of VLAN= above and will enable the VLAN ID for ingress as well.

macvtap.network

[Match]
Name=enp0s25

[Network]
MACVTAP=macvtap-test

systemd.link

Network link configuration is performed by the net_setup_link udev builtin. udev (userspace /dev) is a device manager for the Linux kernel. As the successor of devfsd and hotplug, udev primarily manages device nodes in the /dev directory.