diff options
Diffstat (limited to 'users/tazjin/presentations/systemd-2016')
16 files changed, 346 insertions, 0 deletions
diff --git a/users/tazjin/presentations/systemd-2016/.gitignore b/users/tazjin/presentations/systemd-2016/.gitignore new file mode 100644 index 000000000000..1a38620fe9cc --- /dev/null +++ b/users/tazjin/presentations/systemd-2016/.gitignore @@ -0,0 +1,6 @@ +slides.aux +slides.log +slides.nav +slides.out +slides.snm +slides.toc diff --git a/users/tazjin/presentations/systemd-2016/.skip-subtree b/users/tazjin/presentations/systemd-2016/.skip-subtree new file mode 100644 index 000000000000..108b3507ddd1 --- /dev/null +++ b/users/tazjin/presentations/systemd-2016/.skip-subtree @@ -0,0 +1 @@ +No Nix files will ever be under this tree ... diff --git a/users/tazjin/presentations/systemd-2016/Makefile b/users/tazjin/presentations/systemd-2016/Makefile new file mode 100644 index 000000000000..ac5dde3cb32f --- /dev/null +++ b/users/tazjin/presentations/systemd-2016/Makefile @@ -0,0 +1,11 @@ +all: slides.pdf + +slides.toc: + lualatex slides.tex + +slides.pdf: slides.toc + lualatex slides.tex + +clean: + rm -f slides.aux slides.log slides.nav \ + slides.out slides.toc slides.snm diff --git a/users/tazjin/presentations/systemd-2016/README.md b/users/tazjin/presentations/systemd-2016/README.md new file mode 100644 index 000000000000..7f004b7d14ca --- /dev/null +++ b/users/tazjin/presentations/systemd-2016/README.md @@ -0,0 +1,6 @@ +This repository contains the slides for my systemd presentation at Hackeriet. + +Requires LaTeX, [beamer][] and the [metropolis][] theme. + +[beamer]: http://mirror.hmc.edu/ctan/macros/latex/contrib/beamer/ +[metropolis]: https://github.com/matze/mtheme diff --git a/users/tazjin/presentations/systemd-2016/demo/demo-error.service b/users/tazjin/presentations/systemd-2016/demo/demo-error.service new file mode 100644 index 000000000000..b2d4c9d34799 --- /dev/null +++ b/users/tazjin/presentations/systemd-2016/demo/demo-error.service @@ -0,0 +1,7 @@ +[Unit] +Description=Demonstrate failing units +OnFailure=demo-notify@%n.service + +[Service] +Type=oneshot +ExecStart=/usr/bin/false diff --git a/users/tazjin/presentations/systemd-2016/demo/demo-limits.slice b/users/tazjin/presentations/systemd-2016/demo/demo-limits.slice new file mode 100644 index 000000000000..998185d26177 --- /dev/null +++ b/users/tazjin/presentations/systemd-2016/demo/demo-limits.slice @@ -0,0 +1,7 @@ +[Unit] +Description=Limited resources demo +DefaultDependencies=no +Before=slices.target + +[Slice] +CPUQuota=10% diff --git a/users/tazjin/presentations/systemd-2016/demo/demo-notify@.service b/users/tazjin/presentations/systemd-2016/demo/demo-notify@.service new file mode 100644 index 000000000000..e25524b4e230 --- /dev/null +++ b/users/tazjin/presentations/systemd-2016/demo/demo-notify@.service @@ -0,0 +1,6 @@ +[Unit] +Description=Demonstrate systemd templating by sending a notification + +[Service] +Type=oneshot +ExecStart=/usr/bin/notify-send 'Systemd notification' '%i' diff --git a/users/tazjin/presentations/systemd-2016/demo/demo-path.path b/users/tazjin/presentations/systemd-2016/demo/demo-path.path new file mode 100644 index 000000000000..87f1342da995 --- /dev/null +++ b/users/tazjin/presentations/systemd-2016/demo/demo-path.path @@ -0,0 +1,6 @@ +[Unit] +Description=Demonstrate systemd path units + +[Path] +DirectoryNotEmpty=/tmp/hackeriet +Unit=demo.service diff --git a/users/tazjin/presentations/systemd-2016/demo/demo-stress.service b/users/tazjin/presentations/systemd-2016/demo/demo-stress.service new file mode 100644 index 000000000000..7e14f13e29d9 --- /dev/null +++ b/users/tazjin/presentations/systemd-2016/demo/demo-stress.service @@ -0,0 +1,6 @@ +[Unit] +Description=Stress test CPU + +[Service] +Slice=demo.slice +ExecStart=/usr/bin/stress -c 5 diff --git a/users/tazjin/presentations/systemd-2016/demo/demo-timer.timer b/users/tazjin/presentations/systemd-2016/demo/demo-timer.timer new file mode 100644 index 000000000000..34eccb98b02a --- /dev/null +++ b/users/tazjin/presentations/systemd-2016/demo/demo-timer.timer @@ -0,0 +1,12 @@ +[Unit] +Description=Demonstrate systemd timers + +[Timer] +OnActiveSec=2 +OnUnitActiveSec=5 +AccuracySec=5 +Unit=demo.service +# OnCalendar=Thu,Fri 2016-*-1,5 11:12:13 + +[Install] +WantedBy=multi-user.target diff --git a/users/tazjin/presentations/systemd-2016/demo/demo.service b/users/tazjin/presentations/systemd-2016/demo/demo.service new file mode 100644 index 000000000000..fcc710ad933f --- /dev/null +++ b/users/tazjin/presentations/systemd-2016/demo/demo.service @@ -0,0 +1,6 @@ +[Unit] +Description=Demo unit for systemd + +[Service] +Type=oneshot +ExecStart=/usr/bin/echo "Systemd unit activated. Hello Hackeriet." diff --git a/users/tazjin/presentations/systemd-2016/demo/notes.md b/users/tazjin/presentations/systemd-2016/demo/notes.md new file mode 100644 index 000000000000..b4866b1642bb --- /dev/null +++ b/users/tazjin/presentations/systemd-2016/demo/notes.md @@ -0,0 +1,27 @@ +# simple oneshot + +Run `demo-notify@hello.service` + +# simple timer + +Run `demo-timer.timer`, show both + +# enabling + +Enable `demo-timer.timer`, go to symlink folder, disable + +# OnError + +Show & run `demo-error.service` + +# cgroups demo + +Start `demo-stress.service` without, show in htop, stop +Show slice unit, start slice unit +Add Slice=demo-limits.slice +daemon-reload +Start stress again + +# Proper service + +Look at nginx unit diff --git a/users/tazjin/presentations/systemd-2016/slides.pdf b/users/tazjin/presentations/systemd-2016/slides.pdf new file mode 100644 index 000000000000..384db2a6e0af --- /dev/null +++ b/users/tazjin/presentations/systemd-2016/slides.pdf Binary files differdiff --git a/users/tazjin/presentations/systemd-2016/slides.pdfpc b/users/tazjin/presentations/systemd-2016/slides.pdfpc new file mode 100644 index 000000000000..99326bd8bf4e --- /dev/null +++ b/users/tazjin/presentations/systemd-2016/slides.pdfpc @@ -0,0 +1,85 @@ +[file] +slides.pdf +[notes] +### 1 +### 2 +Let's start off by looking at what an init system is, how they used to work and what systemd does different before we go into more systemd-specific details. +### 3 +system processes that are started include for example FS mounts, network settings, powertop... +system services are long-running processes such as daemons, e.g. SSH, database or web servers, session managers, udev ... + +orphans: Process whose parent has finished somehow, gets adopted by init system +-> when a process terminates its parent must call wait() to get its exit() code, if there is no init system adopting orphans the process would become a zombie +### 4 +Before systemd there were simple init systems that just did the tasks listed on the previous slide. +Init scripts -> increased greatly in complexity over time, look at incomprehensible skeleton for Debian service init scripts +Runlevels -> things such as single-user mode, full multiuser mode, reboot, halt + +Init will run all the scripts, but it will not do much more than print information on success/failure of started scripts + +Init scripts run strictly sequential + +Init is unaware of inter-service dependencies, expressed through prefixing scripts with numbers etc. + +Init will not watch processes after system is booted -> crashing daemons will not automatically restart +### 5 +### 6 +How systemd came to be + +Considering the lack of process monitoring, problematic things about init scripts -> legacy init systems have drawbacks + +Apple had already built launchd, a more featured init system that monitored running processes, could automatically restart them and allowed for certain advanced features -> however it is awful to use and wrap your head around + +Lennart Poettering of Pulseaudio fame and Kay Sievers decided to implement a new init system to address these problems, while taking certain clues from Apple's design +### 7 +Systemd's design goals +### 8 +No more init scripts with opaque effects -> services are clearly defined units +Unit dependencies -> systemd can figure out what can be started in parallel +Process supervision: Unit can be configured in many ways, e.g. always restart, only restart on success etc +Service logs: We'll talk more about this later +### 9 +Units are the core component of systemd that users deal with. They define services and everything else that systemd needs to start and manage. +Note that all these are the names of the respective man page on a system with systemd installed +Types: +systemd.service - processes controlled by systemd +systemd.target - equivalent to "runlevels", grouping of units for synchronisation +systemd.timer - more powerful replacement of cron that starts other units +systemd.path - systemd equvialent of inotify, watches files/folders -> launches units +systemd.socket - expose local IPC or network sockets, launch units on connections +systemd.device - trigger units when certain devices are connected +systemd.mount - systemd equivalent of fstab entries +systemd.swap - like mount +systemd.slice - unit groups for resource management purposes +... and a few more specialised ones +### 10 +Linux cgroups are a new resource management feature added quite a long time ago, but not used much. +Cgroups can be created manually and processes can be moved into them in order to control resource utilisation +Few people used them before systemd, limits.conf was often much easier but not as fine-grained +Systemd changed this +### 11 +Systemd collects standard output and stderr from all processes into its journal system +they provide a tool for querying the log, for example grouping service logs together with correct timestamps, querying, +### 12 +Systemd tooling, most important one is systemctl for general service management +journalctl is the query and management tool for journald +systemd-analyze is used for figuring out performance issues, for example by analysing the boot process, can make cool graphs of dependencies +systemd-cgtop is like top, but not on a process level - it's on a cgroup/slice level, shows combined usage of cgroups +systemd-cgls lists contents of systemd's cgroups to see which services are in what group +there also exist a bunch of others that we'll skip for now +### 13 +### 14 +### 15 +Systemd criticism comes from many directions and usually focuses on a few points +feature-creep: systemd is absorbing a lot of different services +### 16 +explain diagram a bit +### 17 +opaque: as a result, systemd has a lot more internal complexity that people can't easily wrap your mind around. However I argue that unless you're using something like suckless' sinit with your own scripts, you probably have no idea what your init does today anyways +unstable: this was definitely true even in the first stable release, with the binary log format getting corrupted for example. I haven't personally experienced any trouble with it recently though. +Another thing is that services start depending on systemd when they shouldn't, a problem for the BSD world (who cares (hey christoph!)) +### 18 +Despite criticism, systemd was adopted rapidly by large portions of the Linux +Initially in RedHat, because Poettering and co work there and it was clear from the beginning that it would be there +ArchLinux (which I'm using) and a few others followed suit quite quickly +Eventually, the big Debian init system discussion - after a lot of flaming - led to Debian adopting it as well, which had a ripple effect for related distros such as Ubuntu which abandoned upstart for it. \ No newline at end of file diff --git a/users/tazjin/presentations/systemd-2016/slides.tex b/users/tazjin/presentations/systemd-2016/slides.tex new file mode 100644 index 000000000000..c613cefd7ec4 --- /dev/null +++ b/users/tazjin/presentations/systemd-2016/slides.tex @@ -0,0 +1,160 @@ +\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} diff --git a/users/tazjin/presentations/systemd-2016/systemdcomponents.png b/users/tazjin/presentations/systemd-2016/systemdcomponents.png new file mode 100644 index 000000000000..a22c762f7e13 --- /dev/null +++ b/users/tazjin/presentations/systemd-2016/systemdcomponents.png Binary files differ |
