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Diffstat (limited to 'slides.pdfpc')
| -rw-r--r-- | slides.pdfpc | 26 |
1 files changed, 25 insertions, 1 deletions
diff --git a/slides.pdfpc b/slides.pdfpc index 2f6ac472edb5..c4b4bf5e9fc7 100644 --- a/slides.pdfpc +++ b/slides.pdfpc @@ -9,4 +9,28 @@ system processes that are started include for example FS mounts, network setting 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 \ No newline at end of file +-> 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 |