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Since 56b2970 has proven to be a no-go for us, as it breaks existing links, let's embrace the trailing slash and use absolute links everywhere for our pages. This way we'll get around browser cleverly appending the relative link to the current location (since it ends with a slash), and given our docs/ layout is flat it's not much of a hassle either. Converted using this beauty: $ sed -ri 's/(\[.+\]\()([A-Z_]+\))/\1\/\2/g' *.md Resolves: #32088 (again) and #32310
192 lines
8.6 KiB
Markdown
192 lines
8.6 KiB
Markdown
---
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title: Tips And Tricks
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category: Manuals and Documentation for Users and Administrators
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layout: default
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SPDX-License-Identifier: LGPL-2.1-or-later
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---
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# Tips & Tricks
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Also check out the [Frequently Asked Questions](/FAQ)!
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## Listing running services
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```sh
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$ systemctl
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UNIT LOAD ACTIVE SUB JOB DESCRIPTION
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accounts-daemon.service loaded active running Accounts Service
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atd.service loaded active running Job spooling tools
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avahi-daemon.service loaded active running Avahi mDNS/DNS-SD Stack
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bluetooth.service loaded active running Bluetooth Manager
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colord-sane.service loaded active running Daemon for monitoring attached scanners and registering them with colord
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colord.service loaded active running Manage, Install and Generate Color Profiles
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crond.service loaded active running Command Scheduler
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cups.service loaded active running CUPS Printing Service
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dbus.service loaded active running D-Bus System Message Bus
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...
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```
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## Showing runtime status
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```sh
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$ systemctl status udisks2.service
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udisks2.service - Storage Daemon
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Loaded: loaded (/usr/lib/systemd/system/udisks2.service; static)
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Active: active (running) since Wed, 27 Jun 2012 20:49:25 +0200; 1 day and 1h ago
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Main PID: 615 (udisksd)
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CGroup: name=systemd:/system/udisks2.service
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└ 615 /usr/lib/udisks2/udisksd --no-debug
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Jun 27 20:49:25 epsilon udisksd[615]: udisks daemon version 1.94.0 starting
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Jun 27 20:49:25 epsilon udisksd[615]: Acquired the name org.freedesktop.UDisks2 on the system message bus
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```
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## cgroup tree
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```sh
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$ systemd-cgls
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└ system
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├ 1 /usr/lib/systemd/systemd --system --deserialize 18
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├ ntpd.service
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│ └ 8471 /usr/sbin/ntpd -u ntp:ntp -g
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├ upower.service
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│ └ 798 /usr/libexec/upowerd
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├ wpa_supplicant.service
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│ └ 751 /usr/sbin/wpa_supplicant -u -f /var/log/wpa_supplicant.log -c /etc/wpa_supplicant/wpa_supplicant.conf -u -f /var/log/wpa_supplicant.log -P /var/run/wpa_supplicant.pid
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├ nfs-idmap.service
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│ └ 731 /usr/sbin/rpc.idmapd
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├ nfs-rquotad.service
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│ └ 753 /usr/sbin/rpc.rquotad
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├ nfs-mountd.service
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│ └ 732 /usr/sbin/rpc.mountd
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├ nfs-lock.service
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│ └ 704 /sbin/rpc.statd
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├ rpcbind.service
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│ └ 680 /sbin/rpcbind -w
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├ postfix.service
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│ ├ 859 /usr/libexec/postfix/master
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│ ├ 877 qmgr -l -t fifo -u
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│ └ 32271 pickup -l -t fifo -u
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├ colord-sane.service
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│ └ 647 /usr/libexec/colord-sane
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├ udisks2.service
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│ └ 615 /usr/lib/udisks2/udisksd --no-debug
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├ colord.service
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│ └ 607 /usr/libexec/colord
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├ prefdm.service
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│ ├ 567 /usr/sbin/gdm-binary -nodaemon
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│ ├ 602 /usr/libexec/gdm-simple-slave --display-id /org/gnome/DisplayManager/Display1
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│ ├ 612 /usr/bin/Xorg :0 -br -verbose -auth /var/run/gdm/auth-for-gdm-O00GPA/database -seat seat0 -nolisten tcp
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│ └ 905 gdm-session-worker [pam/gdm-password]
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├ systemd-ask-password-wall.service
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│ └ 645 /usr/bin/systemd-tty-ask-password-agent --wall
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├ atd.service
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│ └ 544 /usr/sbin/atd -f
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├ ksmtuned.service
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│ ├ 548 /bin/bash /usr/sbin/ksmtuned
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│ └ 1092 sleep 60
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├ dbus.service
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│ ├ 586 /bin/dbus-daemon --system --address=systemd: --nofork --systemd-activation
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│ ├ 601 /usr/libexec/polkit-1/polkitd --no-debug
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│ └ 657 /usr/sbin/modem-manager
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├ cups.service
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│ └ 508 /usr/sbin/cupsd -f
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├ avahi-daemon.service
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│ ├ 506 avahi-daemon: running [epsilon.local]
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│ └ 516 avahi-daemon: chroot helper
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├ system-setup-keyboard.service
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│ └ 504 /usr/bin/system-setup-keyboard
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├ accounts-daemon.service
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│ └ 502 /usr/libexec/accounts-daemon
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├ systemd-logind.service
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│ └ 498 /usr/lib/systemd/systemd-logind
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├ crond.service
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│ └ 486 /usr/sbin/crond -n
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├ NetworkManager.service
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│ ├ 484 /usr/sbin/NetworkManager --no-daemon
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│ └ 8437 /sbin/dhclient -d -4 -sf /usr/libexec/nm-dhcp-client.action -pf /var/run/dhclient-wlan0.pid -lf /var/lib/dhclient/dhclient-903b6f6aa7a1-46c8-82a9-7f637dfbb3e4-wlan0.lease -cf /var/run/nm-d...
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├ libvirtd.service
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│ ├ 480 /usr/sbin/libvirtd
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│ └ 571 /sbin/dnsmasq --strict-order --bind-interfaces --pid-file=/var/run/libvirt/network/default.pid --conf-file= --except-interface lo --listenaddress 192.168.122.1 --dhcp-range 192.168.122.2,1...
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├ bluetooth.service
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│ └ 479 /usr/sbin/bluetoothd -n
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├ systemd-udev.service
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│ └ 287 /usr/lib/systemd/systemd-udevd
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└ systemd-journald.service
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└ 280 /usr/lib/systemd/systemd-journald
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```
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### ps with cgroups
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```sh
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$ alias psc='ps xawf -eo pid,user,cgroup,args'
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$ psc
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PID USER CGROUP COMMAND
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...
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1 root name=systemd:/systemd-1 /bin/systemd systemd.log_target=kmsg systemd.log_level=debug selinux=0
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415 root name=systemd:/systemd-1/sysinit.service /sbin/udevd -d
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928 root name=systemd:/systemd-1/atd.service /usr/sbin/atd -f
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930 root name=systemd:/systemd-1/ntpd.service /usr/sbin/ntpd -n
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932 root name=systemd:/systemd-1/crond.service /usr/sbin/crond -n
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935 root name=systemd:/systemd-1/auditd.service /sbin/auditd -n
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943 root name=systemd:/systemd-1/auditd.service \_ /sbin/audispd
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964 root name=systemd:/systemd-1/auditd.service \_ /usr/sbin/sedispatch
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937 root name=systemd:/systemd-1/acpid.service /usr/sbin/acpid -f
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941 rpc name=systemd:/systemd-1/rpcbind.service /sbin/rpcbind -f
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944 root name=systemd:/systemd-1/rsyslog.service /sbin/rsyslogd -n -c 4
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947 root name=systemd:/systemd-1/systemd-logger.service /lib/systemd/systemd-logger
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950 root name=systemd:/systemd-1/cups.service /usr/sbin/cupsd -f
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955 dbus name=systemd:/systemd-1/messagebus.service /bin/dbus-daemon --system --address=systemd: --nofork --systemd-activation
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969 root name=systemd:/systemd-1/getty@.service/tty6 /sbin/mingetty tty6
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970 root name=systemd:/systemd-1/getty@.service/tty5 /sbin/mingetty tty5
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971 root name=systemd:/systemd-1/getty@.service/tty1 /sbin/mingetty tty1
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973 root name=systemd:/systemd-1/getty@.service/tty4 /sbin/mingetty tty4
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974 root name=systemd:/user/lennart/2 login -- lennart
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1824 lennart name=systemd:/user/lennart/2 \_ -bash
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975 root name=systemd:/systemd-1/getty@.service/tty3 /sbin/mingetty tty3
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988 root name=systemd:/systemd-1/polkitd.service /usr/libexec/polkit-1/polkitd
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994 rtkit name=systemd:/systemd-1/rtkit-daemon.service /usr/libexec/rtkit-daemon
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...
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```
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## Changing the Default Boot Target
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```sh
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$ ln -sf /usr/lib/systemd/system/multi-user.target /etc/systemd/system/default.target
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```
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This line makes the multi user target (i.e. full system, but no graphical UI) the default target to boot into.
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This is kinda equivalent to setting runlevel 3 as the default runlevel on Fedora/sysvinit systems.
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```sh
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$ ln -sf /usr/lib/systemd/system/graphical.target /etc/systemd/system/default.target
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```
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This line makes the graphical target (i.e. full system, including graphical UI) the default target to boot into.
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Kinda equivalent to runlevel 5 on fedora/sysvinit systems.
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This is how things are shipped by default.
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## What other units does a unit depend on?
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For example, if you want to figure out which services a target like multi-user.target pulls in, use something like this:
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```sh
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$ systemctl show -p "Wants" multi-user.target
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Wants=rc-local.service avahi-daemon.service rpcbind.service NetworkManager.service acpid.service dbus.service atd.service crond.service auditd.service ntpd.service udisks.service bluetooth.service cups.service wpa_supplicant.service getty.target modem-manager.service portreserve.service abrtd.service yum-updatesd.service upowerd.service test-first.service pcscd.service rsyslog.service haldaemon.service remote-fs.target plymouth-quit.service systemd-update-utmp-runlevel.service sendmail.service lvm2-monitor.service cpuspeed.service udev-post.service mdmonitor.service iscsid.service livesys.service livesys-late.service irqbalance.service iscsi.service netfs.service
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```
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Instead of "Wants" you might also try "WantedBy", "Requires", "RequiredBy", "Conflicts", "ConflictedBy", "Before", "After"
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for the respective types of dependencies and their inverse.
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## What would get started if I booted into a specific target?
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If you want systemd to calculate the "initial" transaction it would execute on boot, try something like this:
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```sh
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$ systemd --test --system --unit=foobar.target
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```
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for a boot target foobar.target.
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Note that this is mostly a debugging tool that actually does a lot more than just calculate the initial transaction,
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so don't build scripts based on this.
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