Systemd: Difference between revisions

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=== DNS ===
=== DNS ===


You should probably turn off systemd-resolved and manually configure /etc/resolv.conf, since systemd sucks the chrome off a donkey's ballbearings.
''UPDATE'': it is working now in Ubuntu 20.04 with my dnsmasq DHCP serving up my 192.168.22.1 nameserver, YAY.


  sudo systemctl disable systemd-resolved
Turn it back on:
  sudo systemctl stop systemd-resolved
  sudo su -
  sudo emacs -nw /etc/resolv.conf # use [nameserver 8.8.8.8] if you don't have anything better
rm -f /etc/resolv.conf
ln -s /run/systemd/resolve/resolv.conf /etc/resolv.conf
systemctl unmask systemd-resolved
  systemctl enable systemd-resolved
  dpkg-reconfigure resolvconf
service network-manager restart


=== Log limit ===
Prevent systemd from casually eating your entire drive with logs by clipping it, here:
$ sudo emacs /etc/systemd/journald.conf
[Journal]
# MBM do not let systemd logs fill drive                                                                                                                                                       
SystemMaxUse=200M
Then reload config:
sudo systemctl daemon-reload


=== NTP ===
=== NTP ===
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Use these in place of cron.  Each one typically does one task.
Use these in place of cron.  Each one typically does one task.


    systemd timer services
[https://www.certdepot.net/rhel7-use-systemd-timers/ systemd timer services]
    ----------------------
    https://www.certdepot.net/rhel7-use-systemd-timers/
   
   
    create a script to do the work:
create a script to do the work:
      echo "/usr/sbin/logrotate /etc/logrotate.conf" >/usr/local/sbin/logrotate.sh
echo "/usr/sbin/logrotate /etc/logrotate.conf" >/usr/local/sbin/logrotate.sh
 
create a service file:
nano /usr/lib/systemd/system/logrotate.service
[Unit]
Description=Rotate logs
   
   
    create a service file:
[Service]
      nano /usr/lib/systemd/system/logrotate.service
Type=simple
        [Unit]
ExecStart=/usr/local/sbin/logrotate.sh
        Description=Rotate logs
User=root
   
   
        [Service]
[Install]
        Type=simple
WantedBy=multi-user.target
        ExecStart=/usr/local/sbin/logrotate.sh
 
        User=root
create a timer file:
nano /usr/lib/systemd/system/logrotate.timer
[Unit]
Description=Rotate logs as needed every night at 2am
   
   
        [Install]
[Timer]
        WantedBy=multi-user.target
OnCalendar=*-*-* 02:00:00
Unit=logrotate.service
   
   
    create a timer file:
[Install]
      nano /usr/lib/systemd/system/logrotate.timer
WantedBy=multi-user.target
        [Unit]
        Description=Rotate logs as needed every night at 2am
   
   
        [Timer]
activate on boot:
        OnCalendar=*-*-* 02:00:00
# NOTE you must enable the service (even though not run directly), plus the timer
        Unit=logrotate.service
# then start the timer
systemctl enable logrotate       
        [Install]
systemctl enable logrotate.timer
        WantedBy=multi-user.target
systemctl start logrotate.timer
utils:
    activate on boot:
systemctl is-enabled ####.timer
      # NOTE you must enable the service (even though not run directly), plus the timer
systemctl is-active ####.timer  # to see if timer is active and enabled
      # then start the timer
systemctl start ####      # to run service immediately
      systemctl enable logrotate       
systemctl status ####    # nice status output
      systemctl enable logrotate.timer
systemctl daemon-reload  # to restart services after config changes
      systemctl start logrotate.timer
systemctl list-timers [####*]  # to list timers that start with #####
 
    utils:
=== Creating a custom managed service ===
      systemctl is-enabled ####.timer
 
      systemctl is-active ####.timer  # to see if timer is active and enabled
Let's get an official systemd service going!  This example is for rtorrent on bandit.
      systemctl start ####      # to run service immediately
 
      systemctl status ####    # nice status output
<pre>
      systemctl daemon-reload  # to restart services after config changes
emacs /etc/systemd/system/rtorrent.service
      systemctl list-timers [####*]  # to list timers that start with #####
------------
 
[Unit]
Description=rTorrent
After=network.target
[Service]
User=m
Type=forking
KillMode=none
ExecStart=/usr/bin/screen -d -m -fa -S rtorrent /usr/bin/rtorrent
ExecStop=/usr/bin/killall -w -s 2 /usr/bin/rtorrent
WorkingDirectory=/home/m/download/torrents/rtorrent
[Install]
WantedBy=default.target
 
--------------
systemctl enable rtorrent.service
systemctl start rtorrent
</pre>

Latest revision as of 20:00, 7 November 2022

Systemd has done serious damage to networkmanager dns cron ntp... We have to adapt to it, here we go.

DNS

UPDATE: it is working now in Ubuntu 20.04 with my dnsmasq DHCP serving up my 192.168.22.1 nameserver, YAY.

Turn it back on:

sudo su -
rm -f /etc/resolv.conf
ln -s /run/systemd/resolve/resolv.conf /etc/resolv.conf
systemctl unmask systemd-resolved
systemctl enable systemd-resolved
dpkg-reconfigure resolvconf
service network-manager restart

Log limit

Prevent systemd from casually eating your entire drive with logs by clipping it, here:

$ sudo emacs /etc/systemd/journald.conf 
[Journal]
# MBM do not let systemd logs fill drive                                                                                                                                                         
SystemMaxUse=200M

Then reload config:

sudo systemctl daemon-reload

NTP

DO NOT INSTALL ntp daemon any more, instead we now have systemd-timesyncd. That relies on systemd-networkd. Here's what I did on gold (which needed a specific ntp server)...

sudo apt remove ntp
emacs /etc/systemd/timesyncd.conf # if you need to hit a non-standard ntp server
systemctl status systemd-networkd systemd-timedated systemd-timesyncd
sudo timedatectl set-ntp on
sudo systemctl start systemd-networkd systemd-timedated systemd-timesyncd


Timers

Use these in place of cron. Each one typically does one task.

systemd timer services

create a script to do the work:

echo "/usr/sbin/logrotate /etc/logrotate.conf" >/usr/local/sbin/logrotate.sh

create a service file:

nano /usr/lib/systemd/system/logrotate.service
[Unit]
Description=Rotate logs

[Service]
Type=simple
ExecStart=/usr/local/sbin/logrotate.sh
User=root

[Install]
WantedBy=multi-user.target

create a timer file:

nano /usr/lib/systemd/system/logrotate.timer
[Unit]
Description=Rotate logs as needed every night at 2am

[Timer]
OnCalendar=*-*-* 02:00:00
Unit=logrotate.service

[Install]
WantedBy=multi-user.target

activate on boot:

# NOTE you must enable the service (even though not run directly), plus the timer
# then start the timer
systemctl enable logrotate       
systemctl enable logrotate.timer
systemctl start logrotate.timer

utils:

systemctl is-enabled ####.timer
systemctl is-active ####.timer   # to see if timer is active and enabled
systemctl start ####      # to run service immediately
systemctl status ####     # nice status output
systemctl daemon-reload   # to restart services after config changes
systemctl list-timers [####*]  # to list timers that start with #####

Creating a custom managed service

Let's get an official systemd service going! This example is for rtorrent on bandit.

emacs /etc/systemd/system/rtorrent.service
------------

[Unit]
Description=rTorrent
After=network.target
[Service]
User=m
Type=forking
KillMode=none
ExecStart=/usr/bin/screen -d -m -fa -S rtorrent /usr/bin/rtorrent
ExecStop=/usr/bin/killall -w -s 2 /usr/bin/rtorrent
WorkingDirectory=/home/m/download/torrents/rtorrent
[Install]
WantedBy=default.target

--------------
systemctl enable rtorrent.service
systemctl start rtorrent