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Why won't it boot?
by Chris Walker 15 Nov '14

15 Nov '14

My machine has recently upgraded itself to a new kernel and now it won't boot. It fails after several seconds telling me that various UUIDs don't exist. But they're the same devices that another kernel does run from. The new kernel which doesn't work is 3.14.18-3 and the one that does work - I'm using it now - is 3.12.25-3. I would have said that if the various partitions do exist, then it *should* work so where do I start trying to fault-find this? -- __ __| |_ __ __ .----------------------------------------------. / _/ _` \ V V / | mailto:alug_cdw@the-walker-household.co.uk | \__\__,_|\_/\_/ |______________________________________________|

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[ALUG Announce] ALUG Norwich Pub Meet Thursday 13th November
by Viperfang 10 Nov '14

10 Nov '14

ALUG Announce Please send announcements to Announce(a)lists.alug.org.uk Unsub, change settings via http://lists.alug.org.uk/mailman/listinfo/announce ----- Hello Norwich Aluggers, Our monthly ALUG Norwich social meeting will be held this Thursday, 13th November at The Coach and Horses (82 Thorpe Road, Norwich, NR1 1BA). The meeting officially starts at 8pm, although some people may arrive earlier. More information on those people can be found on the list and the IRC channel. If you are unsure if you will recognise us then make yourself and your intent to attend known by either posting on list or visiting us on IRC so we can look out for you rather than hiding in the corner. Optionally you could ask at the bar if they know where the geeky computer weirdos are and they'll point you in the right direction (seriously!). Another possibility is look for heaps of electronics on a table that may possibly look like movie props that would used for detonating explosives. Feel free to bring electronics/laptops/gadgets to the meet, you will by no means be alone. Ben Bewick aka Viperfang NB: This mail is automated, please refer to the usual sources for more information. ALUG Contact Details: Website : http://www.alug.org.uk/ IRC : #alug on irc.alug.org.uk List : http://lists.alug.org.uk/mailman/listinfo Twitter : http://twitter.com/anglianlug Identica: TBA Facebook: http://www.facebook.com/group.php?gid=2381613902 ----- Send discussion replies to main(a)lists.alug.org.uk (Reply-To set) Unsub, change settings via http://lists.alug.org.uk/mailman/listinfo/announce

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Weird character swapping during typing
by Mark Rogers 09 Nov '14

09 Nov '14

Either I have lost the ability to type or something else is going on. I'm finding characters swapped around in tetx that I ytpe (that's been happening all the way through this email but I left those in to demonstrate). Seems to be mostly in Chrome (I'm using Gmail to send this). Seems a particular issue on my Ubuntu laptop, but also happens on my Kubuntu desktop. Don't see it elsewhere. Thoughts? It seems very bad today. Chrome is also running like a dog despite CPU and memory looking OK in htop. I tend to assume that characters go into a keyboard buffer and out in the same order no matter busy the PC is? Seems particularly bad around spaces, eg lik ethis. -- Mark Rogers // More Solutions Ltd (Peterborough Office) // 0844 251 1450 Registered in England (0456 0902) @ 13 Clarke Rd, Milton Keynes, MK1 1LG

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Getting started with NoSQL
by Mark Rogers 04 Nov '14

04 Nov '14

Everything I am doing here is on Linux but as it has the potential to be cross platform feel free to tell me its off topic and I'll go elsewhere with my tail between my legs. Until last week I had zero understanding of NoSQL. I spent some time going through tutorials (using OrientDB - I have no idea how much of this is generic and how much is DB specific) and now have a broad understanding of a graph database, and the concepts of vertices and edges. I'm hoping for some advice on a sensible schema to get started on a specific application. All I want to do is log data coming from sensors. I haven't decided exactly what yet but assume environmental stuff like temperatures, and other stuff like counters (eg energy usage), speeds, etc. They'll be polled periodically from various devices and stored in the database. In most cases there will be a logical grouping to a set of values (eg they all relate to a single room) but others might be more generic. Once I have the data, there are two things I want to do with it. First: display current data on a web page which is constantly updating and always being displayed. Second, I want to be able to run reports over the historical data. With MySQL I would probably have a script which polled all the sensors and stored everything into one record indexed by time, because it's trivial to dump even large amounts of data into a table that way. Whether or not that was the right way in MySQL I'm sure it would be wrong in Orientdb. My first thought was to create a generic Sample class (type, timestamp, value), and extend that to create new classes for specific types of data (Temperature, etc). Create a new vertex for each sample and (having already created a vertex for each room) link them with edges. However I have no idea how efficient that would be when it comes to extracting all the latest data, or historic data ordered by time. So any guidance would be very gratefully received, Also, I have no idea how well it would perform. A handful of samples every minute would be fine I am sure, but what it if were more like 50-100? And what it they were stored every second? That might not be relevant here but this is a learning exercise and I want to understand this stuff. (50-100 samples per second into a MySQL DB would be no problem even on a Pi, after all, assuming they were stored in a single record as described above.) -- Mark Rogers // More Solutions Ltd (Peterborough Office) // 0844 251 1450 Registered in England (0456 0902) @ 13 Clarke Rd, Milton Keynes, MK1 1LG

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2600 meeting at 18:00 on Friday the 7th November.
by Viperfang 04 Nov '14

04 Nov '14

Quick heads up about this months Norwich 2600 meeting, more info at http://www.norwich2600.co.uk

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Sharing small amounts of data between PCs
by Mark Rogers 03 Nov '14

03 Nov '14

Suppose I have several PCs (call them Raspberry Pis, because they probably will be) each collecting data from local sources (eg temperature data via a local sensor), logging it to a local database, and making it visible via a local display on HDMI and/or via a web browser. If I want to take advantage of the fact that they're all networked and allow each of them to pull the stored data from all their neighbours, what would be the simplest way to achieve this? Database replication etc feels like overkill. I don't really want there to be a "master", I'd like to think of them all as equivalent peers. -- Mark Rogers // More Solutions Ltd (Peterborough Office) // 0844 251 1450 Registered in England (0456 0902) @ 13 Clarke Rd, Milton Keynes, MK1 1LG

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Will two NAT routers 'in series' cause any problems/slowness?
by Chris Green 31 Oct '14

31 Oct '14

I've just got a Mikrotik RB2011 router which I am going to use as the main 'hub' router on my home LAN. Since it doesn't do ADSL itself and I don't have any simple 'modem only' (yes, I know they're not really modems) ADSL boxes I'm going to use my two existing ADSL routers to connect the Mikrotik to the internet. This means that there will be two NAT routers between me (well, eveything on the LAN) and the internet. I can't see that this will cause a problem, can anyone else see anything wrong with this? The Mikrotik will do load balancing and it has the advantage that it can handle more than two WAN connections so I can add my 3G and/or WiFi backup connection while leaving the two ADSL in place. -- Chris Green

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Post-processing files recovered using photorec
by Mark Rogers 31 Oct '14

31 Oct '14

I've just recovered several GB of data using photorec from a family friend's dead NAS backup box. So far so good. But as is common with the methods used by photorec it can generate some very large files which are largely rubbish. Eg tiny gif files being recovered as >1GB because photorec hasn't detected the end of the file. I'm looking for tools that can postprocess these files, but looking around I'm seeing people discussing the problem as if it's just one of those things. Does anyone have any experience of this sort of thing? My typical strategy is to use "find" to locate recovered files by file extension and move them to a directory per file type, then hand the results over to whoever's disk it was. But I know I can do better! For example: The 1GB+ GIF file can be "fixed" using convert or mogrify (from ImageMagick): convert recovered.gif fixed.gif As far as I know that effectively loads the file and re-saves it without making any changes (but all the rubbish gets stripped in the process) - can anyone confirm this? If so: cd recovered/gif && mogrify * .. is a safe way to fix the recovered files. Similarly, .zip files (and related files, such as LibreOffice docs) can have this problem; extracting the zip and recreating it fixes it. Any other tricks I should be aware of? Anyone aware of any tools to automate this? Ideally this should happen in tandem with the recovery; all those wasted GB are reducing the capacity of the destination drive, sometimes to the point that the recovery fails to complete. Mark -- Mark Rogers // More Solutions Ltd (Peterborough Office) // 0844 251 1450 Registered in England (0456 0902) @ 13 Clarke Rd, Milton Keynes, MK1 1LG

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File/directory synchronization (or synchronisation)
by Chris Green 30 Oct '14

30 Oct '14

All the recent discussions on backups and the peer to peer question has suddenly become a bit more relevant to me as I'm playing with Calibre for keeping my E-Books. I installed Calibre on my desktop machine, it's improved quite a bit since I last played with it and it now fits my requirements rather better than before. So I've imported quite a few E-Books into it and have started sorting them out a bit. However I then realised that E-Books in particular need to be able to be carried around with me, so I want them on my laptop as well as on my desktop machine - synchronisation! Initially it feels as if there's a lot of choice but in reality there isn't if you filter with the following basic requirements:- Must work across the 'net in some way or other, just file synchronisation doesn't really do what one wants. It needs to work when not connected as well though so a remote FS is no good. Should update automatically, preferably in 'real time'. Would like it to synchronise existing directories, not require things to be synchronised to be put in a special place. Looking at the Wikipedia list there's only two or three satisfy the first two requirements and adding the third seems to mean nothing does what I want. I guess Conduit might do it but it seems to be dead which is a pity. Owncloud is possibly the least worst and has the advantage (for me) that I have a Owncloud server running already. It expects you to put files in a special place though. -- Chris Green

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How did I break this?
by William Hill 27 Oct '14

27 Oct '14

I've got a linux board that can't connect to anything. It just gives me "192.168.1.1 - no route to host". Won't even ping. Bill PS, I'm logged in using ssh through wifi via router 192.168.1.1

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