Posts

NFS and the 16 groups

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  So, here’s one that someone else solved before me, but it’s really hard to find. Consider this a boost: https://www.xkyle.com/solving-the-nfs-16-group-limit-problem/ The story is: NFS mounts, group permissions and the group limit. Say you’ve got a filesystem mounted from a server over NFS. You’ve got a multi-user environment and a stack of groups to manage permissions, those groups are somehow kept in line by something like LDAP or active directory. You go to cd to a directory (maybe even the mount point) and get permission denied. Something like this: me@box~$ ls /data/somedir ls: cannot open directory /data/somedir: Permission denied (Yes, it’s an unorthodox mount point…) me@box~$ ls /data/somedir -lhd drwxrws--x. 21 notme group5 4.0K May  2 14:32 /data/somedir But you’re definitely in (for sake of argument) group5: me@box:~$ groups group1 group2 group3 group4 group5 group6 group7 group8 group9 group10 group11 group12 group13 group14 group15 group16 group17 group18 group19 group20
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Eldrich filesystem horrors

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  Hopefully you will never see this one, but with Halloween upon us I thought I’d share a file system horror story from the depths of time. I’ve changed some of the names, but this is all true. We have some processes that do a bit of metadata cleaning on datasets, and for a long time they ran on some old Ubuntu boxes (imagine cobwebs in a dark corner of the server room with a flickering light, if you like). One quiet afternoon, a process fell over. When it was noticed and reported a little later I had a look at the logs. There was a mismatch in the number of files that had been copied across for processing, one of the sanity checks the process runs. This was rare, but not strange: they are big datasets and space might run out occasionally. I made sure there was enough free and restarted it, but, when I checked back later, it had failed again. Digging deeper over the next few hours would lead me to a place beyond sanity checking… The process in question copies a lot of files to local s
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Peguinland 25

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In early 2015, in what turned out to be the last article for about 10 years, I wrote: “I started Electric Penguinland as a series of notes-to-self, to write up things that were difficult to discover online.” From 2011 to 2015 (often with quite long gaps) there was a theme, around Linux and music (particularly guitars), and it ran out. I’d got things set up to suit me, there was no point getting more equipment or building even more guitars while I was still trying to learn to play. (Before that 2015 post I’d put up a teaser photo for a second build I did in 2014). In 2016 I broke my wrist and, by the time I was able to comfortably play guitar again, I’d gone backwards enough that relearning everything was just too frustrating. I still mess about sometimes, but I’d moved on to other things. For mostly the same reasons I drifted out of involvement with Fedora Jam, it was no longer something I needed. Meanwhile, Penguinland got dusty. Sometimes a comment might turn up from someone it h
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Peaceful tuning, Pacifica 112

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Hello again! It's been over a year since my last post (Pure Drumming) . I started Electric Penguinland as a series of notes-to-self, to write up things that were difficult to discover online. I'm glad people have found the odd thing I've posted useful, so I'm picking up with the article that I was planning to start last year with: replacing the tuners on a Yamaha Pacifica.
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2015

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 Electric Penguinland Will Return...
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Pure drumming

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All too often I find ways to distract myself when I've intended to do some guitar practice. Recently I thought it would be nice to create some drum tracks to play with. "No problem!" You say, "Use Hydrogen ." This is a start, but what if you don't know much about drumming and find clicking beats on a track comes out a bit flat? The first thing to come to mind was to try some MIDI pads, but that seemed like overkill, especially when something with buttons on it was much closer to hand—my Xbox 360 controller.
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MathJax posts

My posts on the string bend calculator used MathJax to display the equations used. But I ended up struggling a while to get them to work on mobile devices. The problem is this: typically MathJax loading needs to go into the document head, but that means editing your blog template.
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