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Analyzing the system state

Show system status using:

$ systemctl status

List running units:

$ systemctl

or:

$ systemctl list-units

List failed units:

$ systemctl --failed

The available unit files can be seen in /usr/lib/systemd/system/ and /etc/systemd/system/ (the latter takes precedence). List installed unit files with:

$ systemctl list-unit-files

Show the cgroup slice, memory and parent for a PID:

$ systemctl status pid
Start a unit immediately:
# systemctl start unit

Stop a unit immediately:

# systemctl stop unit

Restart a unit
NOTE:  restart in systemd is not equivalent to start stop and start. For example in certain case it does not change ownership of run socket in Docker.

# systemctl restart unit

Ask a unit to reload its configuration:

# systemctl reload unit

Show the status of a unit, including whether it is running or not:

$ systemctl status unit

Check whether a unit is already enabled or not:

$ systemctl is-enabled unit

Enable a unit to be started on bootup:

# systemctl enable unit

Enable a unit to be started on bootup and Start immediately:

# systemctl enable --now unit

Disable a unit to not start during bootup:

# systemctl disable unit

Mask a unit to make it impossible to start it (both manually and as a dependency, which makes masking dangerous):

# systemctl mask unit

Unmask a unit:

# systemctl unmask unit

Show the manual page associated with a unit (this has to be supported by the unit file):

$ systemctl help unit

Reload systemd manager configuration, scanning for new or changed units:

Note: This does not ask the changed units to reload their own configurations. See reload example above.
# systemctl daemon-reload

Power management

polkit is necessary for power management as an unprivileged user. If you are in a local systemd-logind user session and no other session is active, the following commands will work without root privileges. If not (for example, because another user is logged into a tty), systemd will automatically ask you for the root password.

Shut down and reboot the system:

$ systemctl reboot

Shut down and power-off the system:

$ systemctl poweroff

Suspend the system:

$ systemctl suspend

Put the system into hibernation:

$ systemctl hibernate

Put the system into hybrid-sleep state (or suspend-to-both):

$ systemctl hybrid-sleep

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NEWS CONTENTS

Old News ;-)

[Jan 26, 2019] SysVinit to Systemd Cheatsheet

Apr 15, 2015 | FedoraProject
Sysvinit Command Systemd Command Notes
service frobozz start systemctl start frobozz Used to start a service (not reboot persistent)
service frobozz stop systemctl stop frobozz Used to stop a service (not reboot persistent)
service frobozz restart systemctl restart frobozz Used to stop and then start a service
service frobozz reload systemctl reload frobozz When supported, reloads the config file without interrupting pending operations.
service frobozz condrestart systemctl condrestart frobozz Restarts if the service is already running.
service frobozz status systemctl status frobozz Tells whether a service is currently running.
ls /etc/rc.d/init.d/ systemctl (or) systemctl list-unit-files --type=service (or)
ls /lib/systemd/system/*.service /etc/systemd/system/*.service
Used to list the services that can be started or stopped
Used to list all the services and other units
chkconfig frobozz on systemctl enable frobozz Turn the service on, for start at next boot, or other trigger.
chkconfig frobozz off systemctl disable frobozz Turn the service off for the next reboot, or any other trigger.
chkconfig frobozz systemctl is-enabled frobozz Used to check whether a service is configured to start or not in the current environment.
chkconfig --list systemctl list-unit-files --type=service (or) ls /etc/systemd/system/*.wants/ Print a table of services that lists which runlevels each is configured on or off
chkconfig frobozz --list ls /etc/systemd/system/*.wants/frobozz.service Used to list what levels this service is configured on or off
chkconfig frobozz --add systemctl daemon-reload Used when you create a new service file or modify any configuration

[Oct 13, 2018] How to Change the Log Level in Systemd

Apr 01, 2016 | 410gone.click

SyslogLevel=
See syslog(3) for details. This option is only useful when StandardOutput= or StandardError= are set to syslog or kmsg . Note that individual lines output by the daemon might be prefixed with a different log level which can be used to override the default log level specified here.

The interpretation of these prefixes may be disabled with SyslogLevelPrefix= , see below. For details, see sd-daemon(3) . Defaults to info .

[Oct 12, 2018] To change the systemd log level change the ' LogLevel ' parameter in /etc/systemd/system.conf

Highly recommended!
The default in RHEL is way to chatty
Apr 01, 2016 | 410gone.click

The Current Log Level

To check the log level of systemd , which are currently set, and then use the show command of systemctl command.

* To set the 'LogLevel' parameter of -p option.

systemctl -pLogLevel show
LogLevel=info

How to Temporarily Change the Log Level

To temporarily change the log level of systemd , use the set-log-level option of systemd-analyze command.

It is an example to change the log level to notice.

systemd-analyze set-log-level notice

How to Permanently Change the Log Level

To enable the log level you have also changed after a restart of the system , change the ' LogLevel ' of /etc/systemd/system.conf .

It is an example to change the log level to notice.

vi /etc/systemd/system.conf
#LogLevel=info
LogLevel=notice

[Dec 15, 2016] systemd crash course

Notable quotes:
"... Enable or disable a service: ..."
"... Start, stop, restart, reload, status: ..."
"... doesn't actually do remote logging (yet. what else doesn't it do?) ..."
Dec 15, 2016 | thefastestwaytobreakamachine

Systemd crash course

Find "unit" – that's the new name for "init script name" to us oldtimers:

systemctl list-units --type=service
# this one is way more verbose
systemctl list-units

Enable or disable a service:

systemctl enable ossec
systemctl disable ossec

Start, stop, restart, reload, status:

systemctl start sshd
systemctl stop sshd
systemctl restart sshd
systemctl reload sshd
# status, gives some log output too
systemctl status sshd

Check ALL the logs, follow the logs, get a log for a service:

journalctl -l
journalctl -f
journalctl -u sshd

Install a systemd service:
(This is what a systemd service description looks like)

    cat > ossec.service << EOF
[Unit]
Description=OSSEC Host-based Intrusion Detection System

[Service]
Type=forking
ExecStart=/var/ossec/bin/ossec-control start
ExecStop=/var/ossec/bin/ossec-control stop

[Install]
WantedBy=basic.target
EOF

# now copy that file into the magic place, /etc/init.d in the old days
install -Dm0644 ossec.service /usr/lib/systemd/system/ossec.service

# now make systemd pick up the changes
systemctl daemon-reload


      

systemd components

Remote logging

OK so you now know your way around this beast.
Now you want remote logging.

According to the Arch wiki [#], systemd doesn't actually do remote logging (yet. what else doesn't it do?) but it will helpfully spew its logs onto the socket /run/systemd/journal/syslog if you knock twice, gently.

To convince systemd to write to this socket, go to /etc/systemd/journald.conf and set

ForwardToSyslog=yes

then issue a journald restart

systemctl restart systemd-journald

You can install syslog-ng and it should pick up the logs. Test it now by making a log entry with

logger -t WARN zool

and check /var/log/syslog.log

If you have a distro runDemocratic Party Neoliberals Monday morning quarterbackingning systemd, then hopefully syslog-ng will be recent enough to be aware enough of systemd that things should just work at this point.

If it don't, syslog-ng.conf's source src { system(); }; isn't picking up the socket file. Fix this by adding the socket explicitly by changing the source in /etc/syslog-ng/syslog-ng.conf like so:

source src {
  unix-dgram("/run/systemd/journal/syslog");
  internal();
};

if you are working with a laptop or desktop then the console_all on tty12 is handy too:

log { source(src); destination(console_all); };

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[Oct 12, 2018] To change the systemd log level change the ' LogLevel ' parameter in /etc/systemd/system.conf Published on Apr 01, 2016 | 410gone.click

Sites

SysVinit to Systemd Cheatsheet - Fedora Project Wiki

systemd - ArchWiki

Systemd tips and tricks - Bruno's All Things Linux - Scot's Newsletter Forums

Systemd service debugging tips. - CertDepot



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History:

Fifty glorious years (1950-2000): the triumph of the US computer engineering : Donald Knuth : TAoCP and its Influence of Computer Science : Richard Stallman : Linus Torvalds  : Larry Wall  : John K. Ousterhout : CTSS : Multix OS Unix History : Unix shell history : VI editor : History of pipes concept : Solaris : MS DOSProgramming Languages History : PL/1 : Simula 67 : C : History of GCC developmentScripting Languages : Perl history   : OS History : Mail : DNS : SSH : CPU Instruction Sets : SPARC systems 1987-2006 : Norton Commander : Norton Utilities : Norton Ghost : Frontpage history : Malware Defense History : GNU Screen : OSS early history

Classic books:

The Peter Principle : Parkinson Law : 1984 : The Mythical Man-MonthHow to Solve It by George Polya : The Art of Computer Programming : The Elements of Programming Style : The Unix Hater’s Handbook : The Jargon file : The True Believer : Programming Pearls : The Good Soldier Svejk : The Power Elite

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The Last but not Least Technology is dominated by two types of people: those who understand what they do not manage and those who manage what they do not understand ~Archibald Putt. Ph.D


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Last modified: March 12, 2019