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Modularize the systemd features into its own notes
This commit is contained in:
Gabriel Arazas
parent
f868f3b3da
commit
c137dcbdcb
57
notebook/linux.systemd.bootloader.org
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57
notebook/linux.systemd.bootloader.org
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@ -0,0 +1,57 @@
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:PROPERTIES:
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:ID: 8505f1f0-f15b-4b04-91fc-12be01913ce6
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:END:
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#+title: systemd-boot
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#+date: 2021-08-07 20:08:09 +08:00
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#+date_modified: 2021-08-07 20:08:31 +08:00
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#+language: en
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systemd also comes with a bootloader aptly named =systemd-boot= though it only supports UEFI-based firmware.
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Just like GRUB, they can be configured through plain-text files.
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For detailed information about the bootloader, see the manual page =systemd-boot.7=.
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With a complete installation, the bootloader config folder may look like the following list.
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#+begin_src
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/boot/
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`-- loader
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|-- entries # (ref:loader-entries)
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| `-- arch.conf
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|-- loader.conf # (ref:loader-conf)
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`-- random-seed
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#+end_src
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- [[(loader-entries)][=loader/entries/=]] is a directory containing all of the entries available to be booted.
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- [[(loader-conf)][=loader.conf=]] contains the loader configuration.
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Most Linux distros with systemd installed should have a sample config file somewhere. [fn:: In case of Arch Linux, it has an example file at =/usr/share/systemd/bootctl/=.]
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As an example, we'll show what those look like.
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=loader.conf= is the configuration for the boot loader including the timeout seconds among others.
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Here is a sample of a bootloader configuration.
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#+begin_src
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default arch
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timeout 4
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#+end_src
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In this config, this simply makes the =arch= loader entry to be default when no actions has occurred.
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It will start loading it automatically after a timeout of 4 seconds.
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The =arch= loader entry can be found at =${ESP}/loader/entries/arch.conf=.
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The following code block shows what a loader entry looks like.
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#+begin_src
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title Arch Linux
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linux /vmlinuz-linux
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initrd /initramfs-linux.img
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options root="PARTUUID=${PARTUUID}"
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#+end_src
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You can customize and create extra entries for the same installation.
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This is what roam:NixOS does with its package generations, letting the user to boot to a specific point in time from the boot loader.
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Very useful for emergency boots in case the current generation breaks for whatever reason.
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For complete details of the configuration file, you can see =loader.conf.5= manual page.
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24
notebook/linux.systemd.environment-directives.org
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24
notebook/linux.systemd.environment-directives.org
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@ -0,0 +1,24 @@
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:PROPERTIES:
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:ID: 3c67e623-c269-4c9b-9bdf-4ad677d46a35
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:END:
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#+title: systemd environment directives
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#+date: 2021-08-07 19:58:29 +08:00
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#+date_modified: 2021-08-07 19:59:45 +08:00
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#+language: en
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systemd enables setting the environment through environment directives.
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Just like how [[id:c7edff80-6dea-47fc-8ecd-e43b5ab8fb1e][systemd at user-level]], you can set it at user-level by placing them in certain user-level load paths (e.g., =$XDG_CONFIG_HOME/environment.d=).
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It needs a =*.conf= file in one of the load paths (seen from the =environment.d.5= manual page).
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Keep in mind it does not use the shell and instead makes use of shell-like syntax.
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The following code block is an example of setting Nix-related environment variables to enable desktop integrations.
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#+begin_src ini
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# Enable desktop integration with Nix-installed applications.
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NIX_PATH=$HOME/.nix-defexpr/channels${NIX_PATH:+:}$NIX_PATH
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PATH=${PATH:+$PATH:}$HOME/.nix-profile/bin
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XDG_DATA_DIRS=${XDG_DATA_DIRS:+$XDG_DATA_DIRS:}$HOME/.nix-profile/share/
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#+end_src
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18
notebook/linux.systemd.journal.org
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18
notebook/linux.systemd.journal.org
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@ -0,0 +1,18 @@
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:PROPERTIES:
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:ID: d83c099a-fc11-4ccc-b265-4de97c85dcbe
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:END:
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#+title: systemd-journald
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#+date: 2021-08-07 20:12:30 +08:00
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#+date_modified: 2021-08-07 20:17:23 +08:00
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#+language: en
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systemd has a journal service storing logs from units.
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It provides a consistent and structured way how to check the logs.
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The service also has the following interfaces.
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- =journald= is the system logging functionality of systemd.
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- It comes with the system daemon service and the =journalctl= command.
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See [[id:941e0a85-1bb4-45be-a729-1b577c7ee317][Command line: journalctl]] for more details.
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44
notebook/linux.systemd.network.org
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44
notebook/linux.systemd.network.org
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@ -0,0 +1,44 @@
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:PROPERTIES:
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:ID: e4dba4ef-71dd-4d30-9a2c-4ad97223510b
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:END:
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#+title: systemd-networkd
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#+date: 2021-08-07 20:01:23 +08:00
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#+date_modified: 2021-08-07 20:06:47 +08:00
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#+language: en
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With a systemd-ful environment, you can run the network daemon (i.e., =systemd-networkd=).
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Once enabled, you can run =networkctl= to list all of the network devices. [fn:: You can also run ~ip address~ for it.]
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#+begin_src shell :cache yes
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networkctl
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#+end_src
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#+results[84c83a400d07ef38e6813bc9ce677cef8a38bd66]:
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: IDX LINK TYPE OPERATIONAL SETUP
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: 1 lo loopback carrier unmanaged
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: 2 enp1s0 ether routable configured
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: 3 wlan0 wlan routable configured
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:
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: 3 links listed.
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To configure network manager, you can create a network file in one of systemd unit file paths in the system.
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Each of the device will be assigned an IP address.
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You can either assign an IP address or dynamically assign them in some way.
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One of the common ways to do dynamic IP addresses is installing a DHCP server (which is another thing to be configured).
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Here's an example of configuring any wireless devices and assigning a dynamic IP addresses with [[https://wiki.archlinux.org/title/Network_configuration#DHCP][DHCP]].
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#+begin_src
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[Match]
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Type=wlan
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[Network]
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DHCP=yes
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IPv6PrivacyExtensions=yes
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[DHCPv4]
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RouteMetric=1024
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[DHCPv6]
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RouteMetric=1024
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#+end_src
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@ -3,7 +3,7 @@
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:END:
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#+title: Exploring systemd features
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#+date: "2021-05-20 22:37:22 +08:00"
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#+date_modified: "2021-08-02 12:02:46 +08:00"
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#+date_modified: "2021-08-07 20:21:53 +08:00"
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#+language: en
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#+property: header-args :eval no
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@ -16,6 +16,11 @@ Among other things, it has the following list of features.
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- [[id:f1b21fc8-86a5-47cd-b3d8-da6ac7a34427][systemd timers]] which can replace cron for task scheduling.
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- [[id:cd5f0d04-d9bb-44e8-a0f2-630ea58c1e94][systemd services]] along with the usual antics of a service manager such as managing dependencies and commands to run when killed.
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- [[id:a602f900-cdcf-4090-9278-d5926d80eedc][systemd transient units]] for quickly creating and scheduling one-off services.
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- [[id:14b49597-011c-4da1-b955-bed6059af4a3][systemd unit templates]] is handy for managing units that have common structure, enabling to start them quickly and dynamically.
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- [[id:3c67e623-c269-4c9b-9bdf-4ad677d46a35][systemd environment directives]] enable setting environment variables from a systemd-ful session.
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- [[id:e4dba4ef-71dd-4d30-9a2c-4ad97223510b][systemd-networkd]] is the network configuration manager in case you want to do [[id:a208dd50-2ebc-404d-b407-3ec2f556535e][Network configuration in Linux]].
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- [[id:8505f1f0-f15b-4b04-91fc-12be01913ce6][systemd-boot]] is a bootloader mainly for UEFI-based systems.
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- [[id:d83c099a-fc11-4ccc-b265-4de97c85dcbe][systemd-journald]] is the system logging service providing a structured way to manage your logs from different units.
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@ -43,206 +48,3 @@ systemctl show-environment
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systemctl --user start $SERVICE
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#+end_src
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* Unit templates
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You can create unit templates which is useful for simple services that only requires an argument.
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Rather than creating individual simple service files, let systemd handle it.
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For example, you may want to spawn a service for Borgmatic with multiple repos.
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If you don't know templates, the dumb way to serve multiple repos is to create individual unit files for each.
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If you want to schedule them, you also have to create a timer unit for each.
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The more efficient solution is to use templates.
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To make a unit template, there are only a handful of requirements:
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- Addition of =%i= to represent the template value.
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- The unit file name has to end with =@= (e.g., =unit-name@.service=, =unit-name@.timer=).
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This could be compressed into a template for a service unit.
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The following code shows how to create one.
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#+begin_src ini
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[Unit]
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Description=Periodic safety backup for %i
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Documentation=man:borg(1) https://www.borgbackup.org/
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[Service]
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Type=simple
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ExecStart=borgmatic --config %i --verbose
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[Install]
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WantedBy=default.target
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#+end_src
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To use the service, you have to give it a value — e.g., ~systemctl --user start borg-backup@test.yaml.service~.
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That's all good but what about scheduling them?
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What if you want to create an archive every hour starting at 08:00?
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You can just create a templated timer unit.
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#+begin_src ini
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[Unit]
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Description=Periodic safety backup for %i
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Documentation=man:borg(1) https://www.borgbackup.org/
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[Timer]
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Unit=borg-backup@%i.service
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Calendar=08/1:00:00
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Persistent=true
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[Install]
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WantedBy=default.target
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#+end_src
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* Bootloader configuration
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systemd also comes with a bootloader aptly named =systemd-boot= though it only supports UEFI-based firmware.
|
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Just like GRUB, they can be configured through plain-text files.
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|
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For detailed information about the bootloader, see the manual page =systemd-boot.7=.
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With a complete installation, the bootloader config folder may look like the following list.
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#+begin_src
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/boot/
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`-- loader
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|-- entries # (ref:loader-entries)
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| `-- arch.conf
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|-- loader.conf # (ref:loader-conf)
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`-- random-seed
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#+end_src
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- [[(loader-entries)][=loader/entries/=]] is a directory containing all of the entries available to be booted.
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- [[(loader-conf)][=loader.conf=]] contains the loader configuration.
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|
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Most Linux distros with systemd installed should have a sample config file somewhere. [fn:: In case of Arch Linux, it has an example file at =/usr/share/systemd/bootctl/=.]
|
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As an example, we'll show what those look like.
|
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|
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=loader.conf= is the configuration for the boot loader including the timeout seconds among others.
|
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Here is a sample of a bootloader configuration.
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#+begin_src
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default arch
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timeout 4
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#+end_src
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In this config, this simply makes the =arch= loader entry to be default when no actions has occurred.
|
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It will start loading it automatically after a timeout of 4 seconds.
|
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|
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The =arch= loader entry can be found at =${ESP}/loader/entries/arch.conf=.
|
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The following code block shows what a loader entry looks like.
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#+begin_src
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title Arch Linux
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linux /vmlinuz-linux
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initrd /initramfs-linux.img
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options root="PARTUUID=${PARTUUID}"
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#+end_src
|
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|
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You can customize and create extra entries for the same installation.
|
||||
This is what roam:NixOS does with its package generations, letting the user to boot to a specific point in time from the boot loader.
|
||||
Very useful for emergency boots in case the current generation breaks for whatever reason.
|
||||
|
||||
For complete details of the configuration file, you can see =loader.conf.5= manual page.
|
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|
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|
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* Network manager configuration
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:PROPERTIES:
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:ID: e4dba4ef-71dd-4d30-9a2c-4ad97223510b
|
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:END:
|
||||
|
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With a systemd-ful environment, you can run the network daemon (i.e., =systemd-networkd=).
|
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Once enabled, you can run =networkctl= to list all of the network devices. [fn:: You can also run ~ip address~ for it.]
|
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#+begin_src shell :cache yes
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networkctl
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#+end_src
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#+results[84c83a400d07ef38e6813bc9ce677cef8a38bd66]:
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: IDX LINK TYPE OPERATIONAL SETUP
|
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: 1 lo loopback carrier unmanaged
|
||||
: 2 enp1s0 ether routable configured
|
||||
: 3 wlan0 wlan routable configured
|
||||
:
|
||||
: 3 links listed.
|
||||
|
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To configure network manager, you can create a network file in one of systemd unit file paths in the system.
|
||||
Each of the device will be assigned an IP address.
|
||||
You can either assign an IP address or dynamically assign them in some way.
|
||||
One of the common ways to do dynamic IP addresses is installing a DHCP server (which is another thing to be configured).
|
||||
Here's an example of configuring any wireless devices and assigning a dynamic IP addresses with [[https://wiki.archlinux.org/title/Network_configuration#DHCP][DHCP]].
|
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|
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#+begin_src
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[Match]
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Type=wlan
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[Network]
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DHCP=yes
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IPv6PrivacyExtensions=yes
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[DHCPv4]
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RouteMetric=1024
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[DHCPv6]
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RouteMetric=1024
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#+end_src
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* DNS server configuration
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While the network manager is enabled, you can access the internet.
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But only with raw IP addresses (e.g., 1.1.1.1 from Cloudflare, 93.174.95.27 for Library Genesis). [fn:: You can find the IP addresses with DNS clients such as [[https://github.com/ogham/dog][dog]] or the [[https://nodejs.org/api/dns.html][DNS library from NodeJS]].]
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Accessing the domain names as you would browse the web normally is an additional layer of the web.
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To access a domain name, you need a DNS client that can resolve them.
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While there are plenty of DNS resolvers, systemd has a component =systemd-resolved= which you can control with =resolvectl= binary.
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systemd-resolved takes a configuration from =/etc/resolve.conf= which most third-party programs also relies on.
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|
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|
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|
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* Log management
|
||||
|
||||
systemd has a journal service storing logs from units.
|
||||
It provides a consistent and structured way how to check the logs.
|
||||
|
||||
It uses =journalctl= as the command for managing logs.
|
||||
See [[id:941e0a85-1bb4-45be-a729-1b577c7ee317][Command line: journalctl]] for more details.
|
||||
|
||||
#+begin_src shell
|
||||
journalctl --user-unit backup.service --follow --boot
|
||||
#+end_src
|
||||
|
||||
|
||||
|
||||
|
||||
* Environment directive
|
||||
|
||||
systemd enables setting the environment through environment directives.
|
||||
|
||||
Just like how [[id:c7edff80-6dea-47fc-8ecd-e43b5ab8fb1e][systemd at user-level]], you can set it at user-level.
|
||||
Useful for setting specific environment only for that user.
|
||||
|
||||
It needs a =*.conf= file in one of the load paths (seen from the =environment.d.5= manual page).
|
||||
Keep in mind it does not use the shell and instead makes use of shell-like syntax.
|
||||
|
||||
The following code block is an example of setting Nix-related environment variables to enable desktop integrations.
|
||||
|
||||
#+begin_src
|
||||
# Enable desktop integration with Nix-installed applications.
|
||||
NIX_PATH=$HOME/.nix-defexpr/channels${NIX_PATH:+:}$NIX_PATH
|
||||
PATH=${PATH:+$PATH:}$HOME/.nix-profile/bin
|
||||
XDG_DATA_DIRS=${XDG_DATA_DIRS:+$XDG_DATA_DIRS:}$HOME/.nix-profile/share/
|
||||
#+end_src
|
||||
|
||||
@ -3,7 +3,7 @@
|
||||
:END:
|
||||
#+title: systemd timers
|
||||
#+date: 2021-07-19 21:45:47 +08:00
|
||||
#+date_modified: 2021-08-02 11:55:59 +08:00
|
||||
#+date_modified: 2021-08-07 19:29:15 +08:00
|
||||
#+language: en
|
||||
|
||||
|
||||
@ -16,6 +16,8 @@ systemd has different ways to denote time.
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||||
- Timestamps refer to a specific point in time — e.g., =2021-04-02=, =today=, =now=.
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- Calendar events can refer to more than one point of time — e.g., =*-*-4/2=, =Sun,Wed,Fri *-1/2-1/8=.
|
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|
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To find more details about time notation, you can view the =systemd.time.5= manual page.
|
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|
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Here's an example of setting a timer for an example backup service.
|
||||
The following timer unit sets it to execute every day at 18:00.
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|
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@ -36,7 +38,7 @@ WantedBy=graphical.target
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If the timer unit is started, this will trigger =borg-backup.service= from the load path.
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But you can omit it if you named the timer unit file similarly (e.g., =borg-backup.timer= with =borg-backup.service=).
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|
||||
You can find more information about it from the =systemd.time.5= manual page.
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||||
You can find more information about it from the =systemd.timer.5= manual page.
|
||||
Furthermore, systemd has a testing tool for time with ~systemd-analyze {timespan,timestamp,calendar}~.
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|
||||
#+begin_src shell :eval yes
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||||
|
||||
57
notebook/linux.systemd.unit-templates.org
Normal file
57
notebook/linux.systemd.unit-templates.org
Normal file
@ -0,0 +1,57 @@
|
||||
:PROPERTIES:
|
||||
:ID: 14b49597-011c-4da1-b955-bed6059af4a3
|
||||
:END:
|
||||
#+title: systemd unit templates
|
||||
#+date: 2021-08-07 19:55:05 +08:00
|
||||
#+date_modified: 2021-08-07 19:55:26 +08:00
|
||||
#+language: en
|
||||
|
||||
|
||||
You can create unit templates which is useful for simple services that only requires an argument.
|
||||
Rather than creating individual simple service files, let systemd handle it.
|
||||
|
||||
For example, you may want to spawn a service for Borgmatic with multiple repos.
|
||||
If you don't know templates, the dumb way to serve multiple repos is to create individual unit files for each.
|
||||
If you want to schedule them, you also have to create a timer unit for each.
|
||||
|
||||
The more efficient solution is to use templates.
|
||||
To make a unit template, there are only a handful of requirements:
|
||||
|
||||
- Addition of =%i= to represent the template value.
|
||||
- The unit file name has to end with =@= (e.g., =unit-name@.service=, =unit-name@.timer=).
|
||||
|
||||
This could be compressed into a template for a service unit.
|
||||
The following code shows how to create one.
|
||||
|
||||
#+begin_src ini
|
||||
[Unit]
|
||||
Description=Periodic safety backup for %i
|
||||
Documentation=man:borg(1) https://www.borgbackup.org/
|
||||
|
||||
[Service]
|
||||
Type=simple
|
||||
ExecStart=borgmatic --config %i --verbose
|
||||
|
||||
[Install]
|
||||
WantedBy=default.target
|
||||
#+end_src
|
||||
|
||||
To use the service, you have to give it a value — e.g., ~systemctl --user start borg-backup@test.yaml.service~.
|
||||
|
||||
That's all good but what about scheduling them?
|
||||
What if you want to create an archive every hour starting at 08:00?
|
||||
You can just create a templated timer unit.
|
||||
|
||||
#+begin_src ini
|
||||
[Unit]
|
||||
Description=Periodic safety backup for %i
|
||||
Documentation=man:borg(1) https://www.borgbackup.org/
|
||||
|
||||
[Timer]
|
||||
Unit=borg-backup@%i.service
|
||||
Calendar=08/1:00:00
|
||||
Persistent=true
|
||||
|
||||
[Install]
|
||||
WantedBy=default.target
|
||||
#+end_src
|
||||
Loading…
Reference in New Issue
Block a user