[systemd-devel] How to get used to systemd vs init

[Ronny Chevalier]

On Tue, Jun 23, 2015 at 10:16 PM, Chad <ccolumbu at gmail.com> wrote:
> On 6/23/2015 1:01 PM, Reindl Harald wrote:
>>
>>
>>
>> Am 23.06.2015 um 21:45 schrieb Chad:
>>>
>>> The new systemd way would be to type (23 total characters, no tab
>>> complete):
>>> systemctl restart httpd
>>> Maybe I could tab complete systemctl, but I don't currently have a
>>> CentOS 7 system to test on.
>>
>>
>> maybe you should just install CentOS inside a VM and test it
>>
>> [root at srv-rhsoft:~]$ systemctl restart h
>> halt-local.service               haveged.service home.mount
>> hostapd-guest.service
>> httpd-lounge-worker.service      hybrid-sleep.target
>> halt.target                      hibernate.target
>> hostapd-guest-interface.service  hostapd.service httpd.service
>>
>>
>>> The real issue is that I have to know (in the above example) that it is
>>> httpd not http.
>>> With so many systems, distros, and services it is hard to remember every
>>> service name exactly (and some names are very long). For example ntpd
>>> has a d, but nfs does not.
>>> Tab completion fixes this issue for me.
>>>
>>> How can I use tab completion with systemd?
>>
>>
>> as like for any other software - hit the TAB key
>>
>>> #####
>>> 2. How to find all possible services:
>>>
>>> The init way:
>>> ls -l /etc/init/d
>>>
>>> The systemd way:
>>> ls -l /lib/systemd/system/*.service /etc/systemd/system/*.service
>>>
>>> This seems WAY harder and I have to remember 2 locations instead of 1
>>
>>
>> nobody but you installs systemd-units in /etc/ and so you have only one
>> location AND customized ones - with sysvinit you
>> had no way to override /etc/init.d/httpd without doing the work after each
>> update again
>>
>
> Harald,
> Thank you for your reply and time.
>
> I will make some time at some point to install CentOS 7 again, I just don't
> have one installed right now.
>
> #1 I did not know you could tab complete that way! i.e. as part of a command
> argument, not just as part of a path.
> Guess I learned something new after 20 years :)
>
> #2 I can see the advantages of having a local override just like /usr/bin
> has /usr/local/bin.
> Out of curiosity is there a reason the team did not follow the local pattern
> with something like: /lib/systemd/local/system?
> It is easy enough to create an alias on systems I use often, it will just
> take time to learn/memorize the new paths, I am so used to /etc/init.d.
>

See http://www.freedesktop.org/wiki/Software/systemd/TheCaseForTheUsrMerge/
for why /lib/ is not used anymore.

Anyway, /usr is considered to be vendor specific (what your distro
provides you) and you should not modify it. /etc, in the other hand,
is entirely for you. If you want to override a unit configuration, you
do not modify /usr/lib/systemd/system/foobar.service but you put your
version in /etc/systemd/system/foobar.service. Then you reload the
units via systemctl daemon-reload. systemctl also provides a simple
tool to do this:

systemctl edit --full foobar.service

It will copy the unit in /etc and open your editor. When you save and
quit, it will automatically run systemctl daemon-reload. You can also
only modify just one directive of a unit file by using:

systemctl edit foobar.service

It will create /etc/systemd/system/foobar.service.d/override.conf and
open your editor. In this file you just have to put the
lines/directives that you want to modify from the original one,
without having to edit the entire unit.

> ^C
>
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