chore(tazjin): Move my presentations to my user directory r/1090

Change-Id: I72b25680e7167c3a55477111c28b1d4936c60e2c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/606
Reviewed-by: tazjin <mail@tazj.in>

1 files changed, 0 insertions, 85 deletions

diff --git a/presentations/systemd-2016/slides.pdfpc b/presentations/systemd-2016/slides.pdfpc
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-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.
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