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When using ZFS on top of iSCSI devices one needs to deal with the fact that iSCSI devices usually appear late in the boot process. ZFS on the other hand is loaded early and the iSCSI devices are not present at the time ZFS scans available devices for pools to import. This means that not all ZFS pools might be imported after the system has completed boot, even if the underlying devices are present and functional. A quick and dirty solution would be to run  zpool import <poolname> after boot, either manually or from cron. A better, more elegant solution is instead to hook into systemd events and trigger zpool import as soon as the devices are created.

How do you, at once, extend a LVM logical volume on a fleet of identical linux ( Centos ) servers using SaltStack ? Here's how and, thanks to Salt, it only took 5m.

After part 1  of this series I had Salt running properly on all minions. It's now time to get some work done with it. We will start with something simple like making sure that ntp is installed and running on all minions. In order to to do that we will use the Salt  states enforcement feature. The default salt states configuration requires that: state definitions be kept in  /srv/salt the default state be named top.sls We will probably need to create both the directory and the files, which we can do with the following command (check that you are not overwriting your own state, needs to be done on the master only!): mkdir -p /srv/salt cat <<EOF >/srv/salt/top.sls base: '*': - ntp EOF What this state definition means is that the base state requires all nodes (as selected by '*') to apply the ntp state. Since we have not yet defined an ntp state we are going to do it right away: cat <<EOF >/srv/salt/ntp.sls ntp: pkg: - ins...

This post is the first in a series documenting the deployment of Salt on a small network ( ~ 100 hosts, initially targeting only linux-based ones which account for roughly half of it). Due to the low number of hosts I have gone for a single master layout. The linux hosts are for the greatest part running Centos 5.[4,5] in both x86 and x64 favors, and just a couple running SLES. Installing salt master The easiest way to install salt on Centos is to pull in the epel repository  : rpm -Uvh http://download.fedoraproject.org/pub/epel/5/i386/epel-release-5-4.noarch.rpm then install salt with yum: yum install -y salt-master Since minions by default will attempt to connect to the salt master by resolving an host named  salt  I configured a salt cname record for the salt master host in the dns server. At this point the master can be started with: /etc/init.d/salt-master start Note : I don't have firewall or SELinux enabled. In particular SE...

I have just completed an upgrade from OpenNMS 1.8.11 to the latest and greatest 1.10. The upgrade in itself is easy and the guides on the OpenNMS wiki will serve you well. Instead in this post I'll describe a couple of other changes that I made which improved very much the overall performance and responsiveness of the system. One is the upgrade from PostgreSQL  8.4 (which came with CentOS) to 9.1 + tuning. The other is switching from apache to nginx. Upgrading postgres is mostly a matter of taking a backup,  pulling in the right repo , running  yum install  and finally importing the database. Tuning postgres I left opennms running on PostgreSQL 9.1 for a while and then I went checking how well postgres was doing. Postgres 9 already performs significantly better that its 8.x predecessors, but I wanted to do better than out-of-the-box. As the postgres user I logged in into the opennms database to install a utility that will help me estimate how muc...