2e3b03b5ae
Change-Id: I72b25680e7167c3a55477111c28b1d4936c60e2c Reviewed-on: https://cl.tvl.fyi/c/depot/+/606 Reviewed-by: tazjin <mail@tazj.in>
160 lines
4.5 KiB
TeX
160 lines
4.5 KiB
TeX
\documentclass[12pt]{beamer}
|
|
\usetheme{metropolis}
|
|
|
|
\newenvironment{code}{\ttfamily}{\par}
|
|
|
|
\title{systemd}
|
|
\subtitle{The standard Linux init system}
|
|
|
|
\begin{document}
|
|
\metroset{titleformat frame=smallcaps}
|
|
|
|
\maketitle
|
|
|
|
\section{Introduction}
|
|
|
|
\begin{frame}{What is an init system?}
|
|
An init system is the first userspace process (PID 1) started in a UNIX-like system. It handles:
|
|
|
|
\begin{itemize}
|
|
\item Starting system processes and services to prepare the environment
|
|
\item Adopting and ``reaping'' orphaned processes
|
|
\end{itemize}
|
|
\end{frame}
|
|
|
|
\begin{frame}{Classical init systems}
|
|
Init systems before systemd - such as SysVinit - were very simple.
|
|
|
|
\begin{itemize}
|
|
\item Services and processes to run are organised into ``init scripts''
|
|
\item Scripts are linked to specific runlevels
|
|
\item Init system is configured to boot into a runlevel
|
|
\end{itemize}
|
|
|
|
\end{frame}
|
|
|
|
\section{systemd}
|
|
|
|
\begin{frame}{Can we do better?}
|
|
\begin{itemize}
|
|
\item ``legacy'' init systems have a lot of drawbacks
|
|
\item Apple is taking a different approach on OS X
|
|
\item Systemd project was founded to address these issues
|
|
\end{itemize}
|
|
\end{frame}
|
|
|
|
\begin{frame}{Systemd design goals}
|
|
\begin{itemize}
|
|
\item Expressing service dependencies
|
|
\item Monitoring service status
|
|
\item Enable parallel service startups
|
|
\item Ease of use
|
|
\end{itemize}
|
|
\end{frame}
|
|
|
|
\begin{frame}{Systemd - the basics}
|
|
\begin{itemize}
|
|
\item No scripts are executed, only declarative units
|
|
\item Units have explicit dependencies
|
|
\item Processes are supervised
|
|
\item cgroups are utilised to apply resource limits
|
|
\item Service logs are managed and centrally queryable
|
|
\item Much more!
|
|
\end{itemize}
|
|
\end{frame}
|
|
|
|
\begin{frame}{Systemd units}
|
|
Units specify how and what to start. Several types exist:
|
|
\begin{code}
|
|
\small
|
|
\begin{columns}[T,onlytextwidth]
|
|
\column{0.5\textwidth}
|
|
\begin{itemize}
|
|
\item systemd.service
|
|
\item systemd.target
|
|
\item systemd.timer
|
|
\item systemd.path
|
|
\item systemd.socket
|
|
\end{itemize}
|
|
\column{0.5\textwidth}
|
|
\begin{itemize}
|
|
\item systemd.device
|
|
\item systemd.mount
|
|
\item systemd.swap
|
|
\item systemd.slice
|
|
\end{itemize}
|
|
\end{columns}
|
|
\end{code}
|
|
\end{frame}
|
|
|
|
|
|
\begin{frame}{Resource management}
|
|
Systemd utilises Linux \texttt{cgroups} for resource management, specifically CPU, disk I/O and memory usage.
|
|
|
|
\begin{itemize}
|
|
\item Hierarchical setup of groups makes it easy to limit resources for a set of services
|
|
\item Units can be attached to a \texttt{systemd.slice} for controlling resources for a group of services
|
|
\item Resource limits can also be specified directly in the unit
|
|
\end{itemize}
|
|
\end{frame}
|
|
|
|
\begin{frame}{journald}
|
|
Systemd comes with an integrated log management solution, replacing software such as \texttt{syslog-ng}.
|
|
\begin{itemize}
|
|
\item All process output is collected in the journal
|
|
\item \texttt{journalctl} tool provides many options for querying and tailing logs
|
|
\item Children of processes automatically log to the journal as well
|
|
\item \textbf{Caveat:} Hard to learn initially
|
|
\end{itemize}
|
|
\end{frame}
|
|
|
|
\begin{frame}{Systemd tooling}
|
|
A variety of CLI-tools exist for managing systemd systems.
|
|
\begin{code}
|
|
\begin{itemize}
|
|
\item systemctl
|
|
\item journalctl
|
|
\item systemd-analyze
|
|
\item systemd-cgtop
|
|
\item systemd-cgls
|
|
\end{itemize}
|
|
\end{code}
|
|
|
|
Let's look at some of them.
|
|
\end{frame}
|
|
|
|
\section{Demo}
|
|
|
|
\section{Controversies}
|
|
|
|
\begin{frame}{Systemd criticism}
|
|
Systemd has been heavily criticised, usually focusing around a few points:
|
|
\begin{itemize}
|
|
\item Feature-creep: Systemd absorbs more and more other services
|
|
\end{itemize}
|
|
\end{frame}
|
|
|
|
\begin{frame}{Systemd criticism}
|
|
\includegraphics[keepaspectratio=true,width=\textwidth]{systemdcomponents.png}
|
|
\end{frame}
|
|
|
|
\begin{frame}{Systemd criticism}
|
|
Systemd has been heavily criticised, usually focusing around a few points:
|
|
\begin{itemize}
|
|
\item Feature-creep: Systemd absorbs more and more other services
|
|
\item Opaque: systemd's inner workings are harder to understand than old \texttt{init}
|
|
\item Unstable: development is quick and breakage happens
|
|
\end{itemize}
|
|
\end{frame}
|
|
|
|
\begin{frame}{Systemd adoption}
|
|
Systemd was initially adopted by RedHat (and related distributions).
|
|
|
|
It spread quickly to others, for example ArchLinux.
|
|
|
|
Debian and Ubuntu were the last major players who decided to adopt it, but not without drama.
|
|
\end{frame}
|
|
|
|
\section{Questions?}
|
|
|
|
\end{document}
|