August 2014 - main

Alternative question to how to run a command once a second - run a command as root
by Chris Green 16 Aug '14

16 Aug '14

The alternative to running a script once a second (as in my other question) is to use a script that's setuid root - nasty and most systems don't let you do it. I'll explain the problem, I'm reading some analog inputs on a Beaglebone Black and want to display them on a numeric LCD. It's basically a voltmeter and ammeter. Thus I want the display to update fairly frequently. The underlying problem is that because of the (stupid?) way the Beaglebone is configured you have to be root to read the ADC inputs. Thus my original solution was to have a root task running in the background reading the ADC values once a second and writing them to a world readable file. The user task can then read them from file as necessary and display the values or send them to me or whatever. The alternative would be to provide some sort of callable routine that runs with root privilege which can be called as needed from user tasks. This would be a much more elegant solution really as much of the time I don't need 'once a second' frequency, only once an hour for sending values across the internet. It's only when I'm in the same place as the Beaglebone that I want 'once a second' values that I can look at. Is there a neat way of running a bit of Python code with root privilege? Security really isn't terribly important, it's only a little SBC monitoring some values. I suppose I could simply run everything as root but that feels all wrong somehow! :-) -- Chris Green

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Where has my disk space gone?
by Chris Green 15 Aug '14

15 Aug '14

I have an old eeePc which has a 2Gb SSD. I have a minimal Ubuntu installation on it and it works OK. However there seems to be some 'missing' disk space. fdisk seems to return what one would expect:- root@eeepc:~# fdisk -l Disk /dev/sda: 2000 MB, 2000388096 bytes 255 heads, 63 sectors/track, 243 cylinders, total 3907008 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x000312c5 Device Boot Start End Blocks Id System /dev/sda1 * 2048 499711 248832 83 Linux /dev/sda2 501758 3905535 1701889 5 Extended /dev/sda5 501760 3905535 1701888 8e Linux LVM Disk /dev/mapper/eeepc--vg-root: 1170 MB, 1170210816 bytes 255 heads, 63 sectors/track, 142 cylinders, total 2285568 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/mapper/eeepc--vg-root doesn't contain a valid partition table Disk /dev/mapper/eeepc--vg-swap_1: 524 MB, 524288000 bytes 255 heads, 63 sectors/track, 63 cylinders, total 1024000 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/mapper/eeepc--vg-swap_1 doesn't contain a valid partition table BUT why does that /dev/mapper/eeepc--vg-root partition show as only 1.1Gb, there's 1.7Gb or so for it to use in /dev/sda5. In fact what is all that /dev/mapper/eeepc--vg-root stuff about? I don't have anything like it on my other machines. -- Chris Green

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Camera media disk corrupted
by Jenny Hopkins 13 Aug '14

13 Aug '14

Hi All, My camera battery died during a file transfer, with the photographs only partially transferred. After recharging the battery, I'm left with a corrupt file system, with listings such as: -rw-r--r-- 1 jenny jenny 268435456 Jan 1 1980 ??.Ã? -rw-r--r-- 1 jenny jenny 0 Jan 3 1980 Ã? -rw-r--r-- 1 jenny jenny 0 Jan 3 1980 Ã? -rw-r--r-- 1 jenny jenny 0 Dec 31 1979 Ã?.? drwx------ 5183 jenny jenny 655360 Mar 29 2012 DCIM drwx------ 3 jenny jenny 32768 Mar 29 2012 MCSOFQ -r--r--r-- 1 jenny jenny 268435456 Dec 31 1979 ]?MSTICK.â??nd -r--r--r-- 1 jenny jenny 33554432 Dec 31 1979 mstk_?ro.IND d????????? ? ? ? ? ? TRASH-~1 Is there any hope at all of getting any further photos from the disk, or is it a lost cause? DCIM takes an age to open, then refuses to copy any of the listed files to my computer hard drive, mostly complaining of input/output error. ls: cannot access DCIM/!â”‚Ã©(a)xn--~-6baq9uc29df93o.xn----mca0s) Input/output error total 9697785440 d????????? ? ? ? ? ? 01ÎŽ\5iâ?¥â??.ÂµÂ¬/ Thanks, Jenny :-(

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[ALUG Announce] ALUG Norwich Pub Meet Thursday 14th August
by Viperfang 11 Aug '14

11 Aug '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, 14th August 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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Bit OT: Libreoffice Writer macros
by Mark Rogers 07 Aug '14

07 Aug '14

I've never played with LO macros before, and I have no idea if this is possible, but: At a certain point in the document I need to insert the document's filename (easy to do using fields), and then later on to insert the same filename after a simple search+replace operation (which is where I'm stuck). I assume macros are the way to go but if there's a better/different way I'm all ears. -- 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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Can anyone help with a Postfix problem please?
by Barry Samuels 05 Aug '14

05 Aug '14

I bought myself a new computer at the end of last week to replace my aging 32 bit machine. I decided to install Debian Testing/Jessie 64 bit from scratch and set it up to match, roughly, what was on my old machine. I included Postfix which was on my 32 bit machine on the assumption that I could copy the Postfix configuration across and it would work. I have to admit that I find email configuration to be one of the black arts which uses magic incantations. Needless to say it didn't work. After a bit of research I discovered that putting 'inet_protocols = ipv4' in main.cf enabled me to send emails. Some of the sent emails appear to get to their intended destinations and some don't with messages as under: <mywife(a)gmail.com>: host mx1.spamfiltering.com[212.113.130.124] said: 550 relay not permitted! (in reply to RCPT TO command) <me(a)myaddress.co.uk>: host mx1.spamfiltering.com [72.249.150.158] said: 550 81.151.115.33 is listed on sem-black.rbl.spamrl.com. Please organise removal and retry. (in reply to end of DATA command) I have obscured some of the details but it should still give an idea. the ip address 81.151.115.33 is btinternet.com our ISP. Similar emails sent from my old machine don't produce those error messages. Any suggestions would be much appreciated. -- Barry Samuels

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Problem with sound on new install
by Jenny Hopkins 01 Aug '14

01 Aug '14

Hi folks, I posted the following to the ubuntu alsa forums with the hope of some pointers, but nothing has come back. Can anyone from alug offer anything further on this? <snip> I've newly installed ubuntu 14.04 on to a Gigabyte GA-J1800N-D2H board, and am trying to get sound working with a Samsung S24D590L monitor through the HDMI cable. Pulse audio control detects Port: HDMI / DisplayPort (plugged in), and the volume meter is showing it is responding to the levels, but no actual sound can be heard. Alsamixer shows the card as HDA Intel PCH and the chip as Intel Valleyview2 HDMI, and I've checked nothing is muted. Monitor volume is not muted. There is no output from "beep". </snip> I was asked for the output of wget -O alsa-info.sh http://www.alsa-project.org/alsa-info.sh && chmod +x ./alsa-info.sh && ./alsa-info.sh --upload, which is now here: http://www.alsa-project.org/db/?f=1a91c118837f2f6038ddb73c397dae4bf340e0b5 I did wonder if I need to install some dedicated drivers from RealTek, such as LinuxPkg_5.18rc8.tar.bz2? And yes, this is the same board I posted about last week - finally managed to create a dos boot stick it would respond to (had to make it from a virtualbox running windows), upgraded the bios from F2 to F4, and off we went. Thanks, Jenny

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