I have a vm (vm1) on which I installed everything I needed and am running a cronjob every 5 hours lets say.
Now using the snapshot of this vm instance I create many more virtual machines.
Now how do I ensure that my pre-scheduled "every 5 hours cron job" runs on all vms at the same time ?I want them to start at the same time but i am not sure how to synchronize the clock/time on all vms any pointers? My vms are running centos 7
The solution that worked for me was
1) fix network ..
2) and since my vms were running centos .. i ended up using chrony
yum install chriny
systemctl enable chronyd
check by
chronyc tracking
chronyc sources
and make sure you can ping the sources
Related
I'm pretty new to Ceph, so I've included all my steps I used to set up my cluster since I'm not sure what is or is not useful information to fix my problem.
I have 4 CentOS 8 VMs in VirtualBox set up to teach myself how to bring up Ceph. 1 is a client and 3 are Ceph monitors. Each ceph node has 6 8Gb drives. Once I learned how the networking worked, it was pretty easy.
I set each VM to have a NAT (for downloading packages) and an internal network that I called "ceph-public". This network would be accessed by each VM on the 10.19.10.0/24 subnet. I then copied the ssh keys from each VM to every other VM.
I followed this documentation to install cephadm, bootstrap my first monitor, and added the other two nodes as hosts. Then I added all available devices as OSDs, created my pools, then created my images, then copied my /etc/ceph folder from the bootstrapped node to my client node. On the client, I ran rbd map mypool/myimage to mount the image as a block device, then used mkfs to create a filesystem on it, and I was able to write data and see the IO from the bootstrapped node. All was well.
Then, as a test, I shutdown and restarted the bootstrapped node. When it came back up, I ran ceph status but it just hung with no output. Every single ceph and rbd command now hangs and I have no idea how to recover or properly reset or fix my cluster.
Has anyone ever had the ceph command hang on their cluster, and what did you do to solve it?
Let me share a similar experience. I also tried some time ago to perform some tests on Ceph (mimic i think) an my VMs on my VirtualBox acted very strange, nothing comparing with actual bare metal servers so please bare this in mind... the tests are not quite relevant.
As regarding your problem, try to see the following:
have at least 3 monitors (or an even number). It's possible that hang is because of monitor election.
make sure the networking part is OK (separated VLANs for ceph servers and clients)
DNS is resolving OK. (you have added the servername in hosts)
...just my 2 cents...
I am building a mesos cluster from scratch (using Vagrant, which is not relevant for this issue).
OS: Ubuntu 16.04 (trusty)
Setup:
Master -> Runs ZooKeeper, Mesos-master, Marathon and Chronos
Slave -> Runs Mesos-slave
This is my provisioning script for the master node https://github.com/zeitgeist2018/infrastructure/blob/fix-marathon/provision/scripts/install-master.sh.
I have managed to register de slave into Mesos, install Marathon and Chronos frameworks, and run scheduled jobs in Chronos (both with docker and shell commands), but I can't get Marathon to work properly. The UI gets stuck in "Loading applications" as soon as I open it, and when I try to call the API, the request hangs forever with no response. In the API I tried to get simple marathon information and do deployments, both with the same hanging result.
I've been checking Marathon logs but I don't see anything error there. Just a couple of logs that may (or not) be a hint:
[2020-03-08 10:33:21,819] INFO Prompting Mesos for a heartbeat via explicit task reconciliation (mesosphere.marathon.core.heartbeat.MesosHeartbeatMonitor$$anon$1:marathon-akka.actor.default-dispatcher-6)
[2020-03-08 10:33:21,822] INFO Received fake heartbeat task-status update (mesosphere.marathon.core.heartbeat.MesosHeartbeatMonitor:Thread-87)
[2020-03-08 10:33:25,957] INFO Found no roles suitable for revive repetition. (mesosphere.marathon.core.launchqueue.impl.ReviveOffersStreamLogic$ReviveRepeaterLogic:marathon-akka.actor.default-dispatcher-7)
Installing jdk11 and choosing it as default fixed this issue for me without downgrading the Marathon to any other version.
in ubuntu 20.04:
sudo apt install openjdk-11-jre-headless
update-alternatives --config java
I increased the number of cpus, virtual machine in which the marathon was installed to 3 and the problem was solved.
I have managed to make it work. It was as simple as downgrading Marathon to v1.7.189. After that, it starts properly, and the API responds to requests.
Is it possible to install kubernetes by kubeadm init command on system has RAM less than 1GB ?I have tried to install but it failed in kubeadm init command.
As mentioned in the installation steps to be taken before you begin, you need to have:
linux compatible system for master and nodes
2GB or more RAM per machine
network connectivity
swap disabled on every node
But going back to your question, It may be possible to run the installation process, but the further usability is not possible. This configuration will be not stable.
I'm using mesosphere on 3 host over Ubuntu 14.04 as follow:
one with mesos master
two with mesos slave
All work fine, but after restart all physical hosts all scheduled job was lost. It's normal? I'm expected that zookeeper will store the current jobs, then when the system will need restart it, all jobs will be rescheduled after the master boot.
Update:
I'm using marathon and mesos on a same node, and I'm run marathon with flag --zk
With marathon's --zk and --ha enabled, Marathon should be storing its state in ZK and recovering it on restart, as long as Mesos allows it to reregister with the same framework ID.
However, you'll also need to enable the Mesos registry (even for a single master), to ensure that Mesos persists information about what frameworkIds are registered in the event of master failover. This can be accomplished by setting the --registry=replicated_log (default), --quorum=1 (since you only have 1 master), and --work_dir=/path/to/registry (where to store the state).
I solved the problem following this installation instructions: How To Configure a Production-Ready Mesosphere Cluster on Ubuntu 14.04
Although you found a solution, I'd like to explain more to this issue:)
In official doc：http://mesos.apache.org/documentation/latest/slave-recovery/
Note that if the operating system on the slave is rebooted, all
executors and tasks running on the host are killed and are not
automatically restarted when the host comes back up.
So all frameworks on Mesos will be killed after reboot. One way to restart the frameworks is to run all frameworks on Marathon, which will manage other frameworks and restart them in need.
However, then you need to auto-restart Marathon when it's killed. In the digitialocean link you mentioned, the Marathon is installed with script in init.d, so it can be restarted after rebooted. Otherwise, if you installed the Marathon via source code, you can use tools like supervisord to monitor Marathon.
I just completed my vagrant box for a product that made by my company.
I needed that because we're running same product on different
operating systems. I want to serve sites inside virtual machines, I
have questions:
Am I on correct way? Can a virtual machine used as production
server?
If you say yes:
How should I keep virtualbox running? Are there any script or sth
to restart if something crashes?
What happens if somebody accidentally gives "vagrant destroy"
command? What should I do if I don't want to lose my database and user
uploaded files?
We have some import scripts that running every beginning of the
month. sometimes they're using 7gb ram (running 1500 lines of mysql
code with lots of asynchronised instances). Can it be dangerous to run
inside VirtualBox?
Are there any case study blog post about this?
Vagrant is mainly for Development environment. I personally recommend using Type 1 hypervisor (Bare metal), VirtualBox is a desktop virtulization tool (Type 2, running on top of a traditional OS), not recommended for production.
AWS is ok, the VMs are running as Xen guest, Xen is on bare metal;-)
I wouldn't.
The w/ Vagrant + Virtualbox is that these are development instances. I would look at Amazon Web Services for actually deploying your project into the wild.