The kernel ate my packets

Some time ago I had a problem with a server. It had two ethernet interfaces connected to different vlans. The main network traffic went via the default gateway in the first vlan, but there was a listening service in the other interface. Everything was right until we tried to reach the second interface from another node out of the second vlan but near of this. It seemed there was not connection, but as I saw with tcpdump, the traffic arrived.

Somebody has changed all the system permissions

I originally submitted this post to Docker people in the celebration of the 2015 Sysadmin Day, and they selected it as one of their favorite war stories. Now I publish it in my own blog. Some time ago I was working as Linux sysadmin in a major company. Our team were in charge of the operating system, but other teams were the applications administrators. So in some circumstances we allowed them some privilleged commands via sudo.

Running Vagrant on OpenSUSE

Some weeks ago Fedora Magazine published a post about running vagrant in Fedora 22 using the libvirt provider. But if you try to repeat the procedure in OpenSUSE you’ll have to perform some different steps because currently there is not a vagrant package at OpenSUSE (I use 13.2). So you will: install ruby and ruby-devel tsao@mylaptop :~> sudo zypper in ruby ruby-devel download and install the Vagrant package from the project home web.

Notes about time in UNIX and Linux systems (II): NTP

The second part of this post about time management I will write about the NTP and its daemon configuration. As I mentioned in the previous post, if you need a very accurate time the best option is using the implementation of the protocol. If you need security over accuracy, then you can use OpenBSD project implementation. OpenNTPd is not a complete implementation of the protocol, but as usual in the OpenBSD software, it’s a good, well-documented, audited code.

Notes about time in UNIX and Linux systems (I): time zones

I decided to write about handling the time at UNIX/Linux systems because a message like this: [29071122.262612] Clock: inserting leap second 23:59:60 UTC I have similar logs in my servers last June 30, 2015. Of course, I was aware about it some months before and I have to do some work to be ready (kernel/ntpd upgrades depending on the version of the package, we work with 8 main releases of 3 GNU/Linux distributions).

Old habits, new times

Today I begin a new blog. This will be my third project. More than 12 years ago three friends began Juanjo, Cañete and me wrote about technology, the University where we were studying, politics… That was the age when people socialised at blog level, you could trace a social network following the links in the blogs to other blogs. Most of them were written in free services like Blogspot, Photoblog… People left behind the unconfortable, ugly, poorly updated static pages of the 90’s, and new hobbyists and experts in different areas (but with no idea on web developing) began to write and enrich the Wide World Web.