Latest systemd version now contains the systemd-importd daemon .
That means that we can use machinectl to import a tar or a raw image from the internet to use it with the systemd-nspawn command.
so here is an example
from my archlinux box:
# cat /etc/arch-release
Arch Linux release
We can download the tar centos7 docker image from the docker hub registry:
# machinectl pull-tar --verify=no https://github.com/CentOS/sig-cloud-instance-images/raw/79db851f4016c283fb3d30f924031f5a866d51a1/docker/centos-7-docker.tar.xz
... Created new local image 'centos-7-docker'. Operation completed successfully. Exiting.
we can verify that:
# ls -la /var/lib/machines/centos-7-docker
total 28 dr-xr-xr-x 1 root root 158 Jan 7 18:59 . drwx------ 1 root root 488 Feb 1 21:17 .. -rw-r--r-- 1 root root 11970 Jan 7 18:59 anaconda-post.log lrwxrwxrwx 1 root root 7 Jan 7 18:58 bin -> usr/bin drwxr-xr-x 1 root root 0 Jan 7 18:58 dev drwxr-xr-x 1 root root 1940 Jan 7 18:59 etc drwxr-xr-x 1 root root 0 Nov 5 2016 home lrwxrwxrwx 1 root root 7 Jan 7 18:58 lib -> usr/lib lrwxrwxrwx 1 root root 9 Jan 7 18:58 lib64 -> usr/lib64 drwxr-xr-x 1 root root 0 Nov 5 2016 media drwxr-xr-x 1 root root 0 Nov 5 2016 mnt drwxr-xr-x 1 root root 0 Nov 5 2016 opt drwxr-xr-x 1 root root 0 Jan 7 18:58 proc dr-xr-x--- 1 root root 120 Jan 7 18:59 root drwxr-xr-x 1 root root 104 Jan 7 18:59 run lrwxrwxrwx 1 root root 8 Jan 7 18:58 sbin -> usr/sbin drwxr-xr-x 1 root root 0 Nov 5 2016 srv drwxr-xr-x 1 root root 0 Jan 7 18:58 sys drwxrwxrwt 1 root root 140 Jan 7 18:59 tmp drwxr-xr-x 1 root root 106 Jan 7 18:58 usr drwxr-xr-x 1 root root 160 Jan 7 18:58 var
Now test we can test it:
[root@myhomepc ~]# systemd-nspawn --machine=centos-7-docker
Spawning container centos-7-docker on /var/lib/machines/centos-7-docker. Press ^] three times within 1s to kill container. [root@centos-7-docker ~]# [root@centos-7-docker ~]# [root@centos-7-docker ~]# cat /etc/redhat-release CentOS Linux release 7.4.1708 (Core) [root@centos-7-docker ~]# [root@centos-7-docker ~]# exit logout Container centos-7-docker exited successfully.
and now returning to our system:
[root@myhomepc ~]# [root@myhomepc ~]# [root@myhomepc ~]# cat /etc/arch-release Arch Linux release
Before we start, let’s clarify some things.
systemd’s Timers are units. Units are the simplest form of systemd files. Units are describing “when and if” a unit service “should or must” run, based on real or relative time.
A real time example is similar to a cron job entry. You can find out all the configuration settings/values for OnCalendar here.
- A relative time example is more close to something like:
“Run this unit service, ten minutes after boot, before this service and also that services must have already been started cause I am depend on them.”
List of systemd-timers
To view the declared timers on a systemd, run the below command:
$ systemctl list-timers
we can see all timers, even the in-active ones, with:
# systemctl list-timers --all
one simple example
ok, let’s start with an example.
I’ll use the /usr/local/bin directory to store my custom scripts, as this directory is in the PATH enviroment variable and I can run these scripts from anywhere.
Our systemd unit files, must be under the /etc/systemd/system/ directory.
Part One: The Script
As an example, the script will mount some volumes after boot time.
The basic script contents the below lines:
# cat /usr/local/bin/mount.volumes.sh
#!/bin/sh /usr/bin/mount /mnt/backup /usr/bin/mount /var/lib/docker
and make it executable:
# chmod +x /usr/local/bin/mount.volumes.sh
You can run this script, once or twice to see if everything goes as planned.
Part Two: The Service
Now it’s time to create a systemd service unit:
# vim /etc/systemd/system/mount.volumes.service
[Unit] Description=Mount Backup & Docker Volume Service [Service] Type=simple ExecStart=/usr/local/bin/mount.volumes.sh [Install] WantedBy=multi-user.target
Part Three: The Timer
Now it is time to create the systemd timer unit:
# vim /etc/systemd/system/mount.volumes.timer
We have to decide when we want to service to run.
eg. Every day, but 45sec after boot
[Unit] Description=Mount Backup & Docker Volume @ reboot [Timer] OnBootSec=45sec OnUnitActiveSec=1day Unit=mount.volumes.service [Install] WantedBy=multi-user.target
Time to wait after booting before we run first time: OnBootSec
- Time between running each consecutive time: OnUnitActiveSec
Part Four: Enable Service
Be aware, we havent finished yet!
Check that systemd can identify these files:
# systemctl list-unit-files | egrep mount.volumes
mount.volumes.service disabled mount.volumes.timer disabled
We can run the systemd service by hand:
# systemctl start mount.volumes.servicee
and see the ouput/results via journalct:
# journalctl -f
Part Five: Enable Timer
finally we need to start & enable (so that runs after reboot) the timer:
# systemctl start mount.volumes.timer
# systemctl enable mount.volumes.timer
Created symlink /etc/systemd/system/multi-user.target.wants/mount.volumes.timer → /etc/systemd/system/mount.volumes.timer.
# systemctl list-timers | egrep mount.volume
Sat 2018-01-27 09:51:01 EET 23h left Fri 2018-01-26 09:51:01 EET 1min 16s ago mount.volumes.timer mount.volumes.service
# systemctl list-unit-files | egrep mount.volume
systemctl list-unit-files | egrep mount.volume mount.volumes.service disabled mount.volumes.timer enabled
To all the systemd haters, I KNOW, its one line on crontab !
If you are not using your PC/laptop as a server, then 99,99% you dont need network at the boot time.
Disabling NetworkManager can speed up your machine.
> sudo systemctl disable NetworkManager
Of course we all need network, so tell your machine to start NetworkManager after your boot process. And you can do that by editing your crontab as root:
> sudo -s # crontab -e
@reboot systemctl start NetworkManager
try this and measure the time you have saved by
before and after .
I’ve recently bought a new laptop.
It has a hybrid disk (470G HDD and a 30G SSD).
On the 30G ssd disk i’ve rsynced my archlinux from my previous laptop to the new one.
The boot process takes almost a full two minutes !
I thought i was drafting to the dark side and my sanity wasnt as good as a couple days ago.
After asking to archlinux forum, they suggest to use
# journalctl -b
I was thinking to convert to systemd for quite some time now
So every time someone mentioned something about systemd (on the internet), i was reading his/her story as my life depend on it.
I am using archlinux so when i’ve read Jason’s blog post,
i was very happy. After a few days, Allan post a similar post
and that was the moment i told my self: “It’s time, i can blame Allan for breaking my system”
I run this command
# pacman -S systemd systemd-arch-units systemd-sysvcompat
and removed sysvinit & initscripts also.
Noticed that /etc/rc.conf became /etc/rc.conf.pacsave
and rebooted my machine.
How difficult is that ?
There was also a few steps that i needed to do.
After that was trivial to enable my services.
I have only a few of them:
# grep DAEMONS /etc/rc.conf.pacsave DAEMONS=(syslog-ng network crond dbus avahi-daemon cupsd xinetd)
I use static network at work.
Followed this link to create my network service.
vim /etc/conf.d/network vim /etc/systemd/system/network.service # systemctl status network # systemctl enable network.service
# systemctl status syslog-ng # systemctl enable syslog-ng.service
be aware that cron is cronie !
systemctl status crond.service systemctl enable cronie.service
systemctl status avahi-daemon systemctl enable avahi-daemon.service
dbus was already enabled
systemctl status dbus
be aware that cupsd is cups
systemctl status cupsd systemctl enable cups.service
systemctl status xinetd systemctl enable xinetd.service
It was simplest than converted from grub to grub2 !