Hi Owen, It would help to provide one or two use cases where (C) solves a problem that (B) (that is the current ceph-detect-init approach) does not solve. I sense there is something better in (C) but I can't think of a use case just now (maybe because I've been thinking about erasure code all day :-). Cheers On 11/05/2015 18:29, Owen Synge wrote: > Dear all, > > Many init systems are used in linux now. Some ceph code needs to know > the init system. (I must admit I have not looked into Solaris, MacOS and > BSD and probably should have) > > It would be nice to have one function that detects the init system > > Since the init system can be specified in ceph and ceph-deploy > explicitly it seems to be its reasonable to fail clearly to detect init > system. > > I see 4 ways I can see to detect init system. > > (A) Check pid 1. > (B) Use a database of OS to init mapping / compile time. > (C) look for init manipulation tools and infure the init system from tools. > > Comments: > ~~~~~~~~ > > (A1) systmd can be detected easily with. > > grep -qs systemd /proc/1/comm > > (A2) With init scripts such as its hard to know what the init system. > > (B1) For operating systems like RHEL, SLE, CENTOS, Fedora and scientific > linux this works well. > > (B2) FOr operating systems like newer debian and ubuntu releases more > than one init system can be installed and used on the OS, so making a > database / doing it at compile time are not practical on all OS's > > (C1) This is fairly reliable. > > (C2) sysV tools have compatibility scripts / programs on other platforms > so if you use a points system for each init system helper script you can > infure systemd over sysV if sytemctrl exists for example. > > So to summarise this: > ~~~~~~~~~~~~~~~~~~~~ > > (1) No one system is perfect in all cases. > (2) Combined these systesm can provide reliable init system detection. > > My proposed approach. > ~~~~~~~~~~~~~~~~~~~~ > > (I) Use all three approaches where each approach can provide and answer, > or fail to provide an answer. > > (II) Should any approaches disagree -> fail to detect init system. > > (III) Should all approaches agree -> then return init system. > > (III) Should no approaches provide an init system -> fail to return init > system. > > Comments > ~~~~~~~~ > > This multi layered and comparing way of doing init systems may seem > complete overkill, or maybe its useful. > > What do you guys think? > > Best regards > > Owen > > > > > > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Loïc Dachary, Artisan Logiciel Libre
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