Linux

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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).

Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.

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After almost half a century, I'm still doing it... (lemmy.sdf.org)

submitted 4 days ago by ExtremeDullard@lemmy.sdf.org to c/linux@lemmy.ml

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So I'm working on a server from home.

I do a cat /sys/class/net/eth0/operstate and it says unknown despite the interface being obviously up, since I'm SSH'ing into the box.

I try to explicitely set the interface up to force the status to say up with ip link set eth0 up. No joy, still unknown.

Hmm... maybe I should bring it down and back up.

So I do ip link set eth0 down and... I drive 15 miles to work to do the corresponding ip link set eth0 up

50 years using Unix and I'm still doing this... 😥

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[–] toynbee@lemmy.world 15 points 3 days ago* (last edited 3 days ago)

A decade and change ago, in a past life, I was tasked with switching SELinux to permissive mode on the majority of systems on our network (multiple hundreds, or we might have gotten above one thousand at that point, I don't recall exactly). This was to be done using Puppet. A large number of the systems, including most of our servers, had already been manually switched to permissive but it wasn't being enforced globally.

Unfortunately, at that point I was pretty familiar with Puppet but had only worked with SELinux a very few times. I did not correctly understand the syntax of the config file or setenforce and set the mode to ... Something incorrect. SELinux interpreted whatever that was as enforcing mode. I didn't realize what I had done wrong until we started getting alerts from throughout the network. Then I just about had a panic attack when I couldn't login to the systems and suddenly understood the problem.

Fortunately, it's necessary to reboot a system to switch SELinux from disabled to any other mode, so most customer facing systems were not impacted. Even more fortunately, this was done on a holiday, so very few customers were there to be inconvenienced by the servers becoming inaccessible. Even more fortunately, while I was unable to access the systems that were now in enforcing mode, the Puppet agent was apparently still running ... So I reversed my change in the manifest and, within half an hour, things were back to normal (after some service restarts and such).

When I finally did correctly make the change, I made sure to quintuple check the syntax and not rush through the testing process.

edit: While I could have done without the assault on my blood pressure at the time, it was an effective demonstration of our lack of readiness for enforcing mode.