Mr. Chevalier,
Thank you for your time and reply.
On 6/23/2015 1:30 PM, Ronny Chevalier wrote:
On Tue, Jun 23, 2015 at 9:45 PM, Chad <ccolu...@gmail.com> wrote:
I am sure this is the wrong place to send this e-mail, but I could not
find
another place to send it.
Hi,
It is the good place :)
Great, thanks.
I want to learn and use systemd, but have run into a few problems on my
way.
Please don't see this as an attack on systemd, I want to learn something
new, but change is hard.
I am an old school kind of sysadmin and I am planning on moving from
CentOS
6 to CentOS 7, but I am having trouble with systemd. I am hoping you know
some shortcuts/tricks to help me learn the new way.
#####
1. I can't spell. With init I don't have to know how to spell things
because
I have tab complete. I use tab complete for almost every command I type.
For
example:
/e<tab> gets -> /etc/
/etc/in<tab> gets -> /etc/init
/etc/init.<tab> gets -> /etc/init.d/
/etc/init.d/ht<tab gets -> /etc/init.d/httpd
/etc/init.d/httpd restart
So I entered 19 characters and got 25 with tab complete.
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.
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?
If you use either bash or zsh, systemd provides shell completion for them.
You could do something like:
systemctl start htt<tab>
systemctl st<tab>
or else, and it will complete it.
I use bash. This is a cool trick that systemd has over init.d. I know not
all programs can do that shell completion, for example /etc/init.d/httpd
res<tab> does not work (I try it all the time out of tab completion habit!).
#####
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.
There is:
systemctl list-unit-files
It lists all the units installed on your system. In systemd a unit is
a configuration file that can describe a service, a mount point, a
device,... So a service is a subtype of unit, see "man 5 systemd.unit"
for more information.
So if you want to only display the services, you just have to specify the
type
systemctl list-unit-files --type=service
Ok, so that is a lot more to remember than ls -l /etc/init.d, but I can
learn it.
#####
3. List all services and their start levels:
In systemd world, start levels equivalent are the targets (see man 5
systemd.target). A target is a synchronisation point between multiple
units. For example, there is sysinit.target which is the
synchronization point for early boot services. This way a unit can ask
to be started only after a specific target, for example.
The init way (all services):
chkconfig --list
The init way (only active services. I use this a lot):
chkconfig --list | grep :on
The systemd way (all services):
systemctl list-unit-files --type=service
The systemd way (only active services, I don't know how to do this).
systemctl ???
With systemctl you can provide a filter according to the current state
of a unit. If you want to list all the active service, you can do:
systemctl --state=active --type=service list-units
Ok, again more to type and remember, but memorization is not out of the
question.
#####
4. What about the many programs that rely on /etc/init.d/<service>
status/start/stop/restart
I have many services that are monitored by nagios or cron jobs (like
logrotate) that rely on /etc/init.d/<service> status/start/stop/restart.
I don't want to change them because right now they work on every server
and
I don't want to have to maintain 2 versions of the code or hunt them all
down.
There is systemd-sysv-generator which creates wrapper .service for
sysv scripts automatically at boot. But you need to specify additional
headers if you want to use ordering. See man systemd-sysv-generator.
That is what I am looking for (systemd-sysv-generator), but does that mean
systemd will not use the .service files and the system will go back to
running all start-up scripts in order via init.d style S01-S99?
I don't really care that much as boot time does not matter (I rarely reboot
and always have a secondary server that can take the load. I run all
clusters or active/backup.)
