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Disk errors causing system to lock
by Mark Rogers 01 Oct '15

01 Oct '15

This is something I've noticed before and I figured it was time I understood what was going on. If I try to access bad sectors on a failing disk my entire PC will often lock up at any point requiring disk access, even off good disks. Why is this? Eg: I am using ddrescue to recover data from a failing disk (so that disk isn't mounted and isn't in use in any way other than for data recovery). When it tries to read a bad sector, ddrescue will understandably get stuck for several seconds [1]. However, in another terminal window (or other application), whilst the bad sector is being attempted, anything which requires disk access (eg trivial operations like "ls" or command completion using tab) will hang until the timeout on the bad disk read. Why is this? I assume it's some kind of locking taking place but I don't understand why reading (eg) /dev/sdb should lock any operations on /dev/sda etc. And ref: [1]: What determines the time that it takes for an attempt to read a bad sector to time out? This is on an Ubuntu 14.04.1 desktop, although I've seen it elsewhere. Mark -- Mark Rogers // More Solutions Ltd (Peterborough Office) // 0844 251 1450 Registered in England (0456 0902) 21 Drakes Mews, Milton Keynes, MK8 0ER

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2600 meeting at 18:00 on Friday the 2nd October.
by Viperfang 29 Sep '15

29 Sep '15

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

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Some questions in and around wifi management
by Chris Green 22 Sep '15

22 Sep '15

I have been spending a lot of time recently trying to get WiFi connections to work reliably. I'm learning, but mostly learning that I don't often know what I'm doing! :-) Firstly I don't think Network Manager is always particularly helpful, for example I'm using WiFi tethering at the moment but also want to turn it off sometimes and see if any local hotspots are available. There seems no way to make Network Manager re-scan, it obstinately continues to show my tethering WiFi when I *know* it's turned off. This rather reduces my confidence in other signals it shows. I have played with using wpa_gui which seems to be more able to do what I want but I don't really understand how it interacts (or not) with Network Manager. Could I uninstall Network Manager and use wpa_gui exclusively? (However then I don't have a way to configure a hard-wired ethernet connection if there is one) E.g. does the 'Connect' button in wpa_gui do all that's necessary or would I have to do the DHCP client, routing, etc., in adddition? Are there any good tutorials about this sort of stuff, or even books? I don't want anything *too* basic, I can get our domestic WiFi working fine without a problem, in that sort of situation Network Manager does a pretty good job. It's when things get a bit more difficult with weaker signals (and sometimes *lots* of them) that I need some help. Oh, and another problem I'm having. I have a Raspberry Pi with an external USB WiFi (long wire with a WiFi with aerial on the end of it) and I'm using some direct manipulation of wpa_supplicant (i.e. built a custom configuration with details found on the 'net) to get it to connect to a WiFi hotspot that uses EAP-SIM authentication. This also involves reading a key from a USB SIM card reader. Much to my surprise I actually got this to work, however my attempts to automate it at system power-up have not worked at all well. I can repeatedly get it to work manually, i.e. by entering commands but I suspect some of the commands fire off background processes and thus automating it is harder than just doing the same thing from rc.local. I have done quite a lot of stuff with rc.local in the past and also with cron jobs and I think I know most of the normal wrinkles. There's just something more going on here, particularly with the wpa_supplicant stuff. Any/all help would be very welcome. -- Chris Green

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Shorewall messages
by Chris Walker 19 Sep '15

19 Sep '15

Hello, If I run dmesg, it scrolls away with loads of this type of message :- [ 9958.682112] Shorewall:net-fw:DROP:IN=enp6s0 OUT= MAC=40:61:86:05:f9:31:00:24:a5:bd:b4:dc:08:00 SRC=192.168.1.1 DST=192.168.1.11 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=53299 DF PROTO=TCP SPT=43075 DPT=80 WINDOW=5840 RES=0x00 SYN URGP=0 In an effort to fix this, I've looked at the installed packages and I see that not only do I have shorewall installed, but also shorewall6. Should I have both? I've looked online at this page to start with - http://www.shorewall.net/manpages6/shorewall6-zones.html - but I can't see which bits of the system are causing the error and hence which bits I should change. So, what can I do to suppress these messages as they're filling up the disc? Any help appreciated. -- __ __| |_ __ __ .----------------------------------------------. / _/ _` \ V V / | mailto:alug_cdw@the-walker-household.co.uk | \__\__,_|\_/\_/ |______________________________________________|

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mailman/apache2.4/cgi-bin issues
by Jenny Hopkins 09 Sep '15

09 Sep '15

Hullo, I'm struggling to get mailman up and running again after changing a virtual server to a new platform, upgrading to debian jessie in the process. I've made the permissions on the new platform for /usr/lib/cgi-bin/mailman identical: (e.g.):-rwxr-sr-x 1 root list 10K Apr 6 16:45 admin I've altered /etc/group to match the old server like this: list:x:38:lurker lurker:x:109:list,www-data /etc/mailman/apache.conf contains these lines: ScriptAlias /cgi-bin/mailman/ /usr/lib/cgi-bin/mailman/ Alias /pipermail/ /var/lib/mailman/archives/public/ Alias /images/mailman/ /usr/share/images/mailman/ <Directory /usr/lib/cgi-bin/mailman/> AllowOverride None Options ExecCGI AddHandler cgi-script .cgi Require all granted </Directory> <Directory /var/lib/mailman/archives/public/> Options FollowSymlinks AllowOverride None Require all granted </Directory> <Directory /usr/share/images/mailman/> AllowOverride None Require all granted </Directory> My first issue is that all site links point to {server}/cgi-bin/mailman/{file}, which gives a "You don't have permission to access /cgi-bin/mailman/create on this server." warning, but if I manually change that to {server}/mailman/{file}, it works. The second issue is that although the link to the archives displays the messages fine, the overview mailman doesn't seem to think I have any existing lists, although /var/lib/mailman is fully synced from the old server. I can't seem to find any file that holds this information. (There is a third that in when I click on one of the mailing list titles, the actual message can't be found, but that's probably moving on to lurker issues). Any ideas welcome! Thanks, Jenny

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LVM /home partition not mounting at boot
by Richard Lewis 08 Sep '15

08 Sep '15

Hello ALUG, For a couple of weeks now I've been getting this problem on my Debian "unstable" laptop. I use LVM for the partitions on my HDD and I'm finding that, maybe three out of four boots, the partition where /home is mounted doesn't get activated. It uses systemd for booting. The boot sequence continues as normal (AFACT) until after [ OK ] Mounted /boot Then it waits for a bit, then I see: [****] A start job is running for dev-mapper-slab/x2dhome.device (42s / 1min 30s) Then after the alloted time, it drops me into "emergency mode". I enter the root password and I can then get the logical volume for /home to mount: # vgchange -ay slab i.e. I set the slab volume group as active and all its logical volumes become active. I can also see from here that, while the other two logical volumes in my volume group are both LV status available (these are /dev/slab/root, where / is mounted, and /dev/slab/swap_1 which is where swap is), the /dev/slab/home logical volume is: LV status NOT available After I issue the vgchange command, I see the kernel message: EXT4-fs (dm-2): mounted filesystem with ordered data mode. Opts: (null) I can then exit "emergency mode" and booting proceeds to the login prompt. From then onwards everything is normal. I've been looking for possible solutions to this and I've tried: * adding lvmwait=/dev/mapper/slab-home to the kernel boot options. This didn't make any difference. * checking the auto_activation_volume_list. At the moment it's undefined, which apparently means that any (all?) volumes can be auto-activated which sounds fine. Any ideas what's going on here? I've been using this LVM set up since the laptop was new (so for 2.5 years) and I've not had this problem before. I tend to keep my packages fairly up-to-date by upgrading every week or so. I guess it's possible some recent upgrade has changed something, but I can't think what. And if it was something that affected lots of people, you'd expect the Web to have some evidence of that, and for there to be some fix on the way. I'm also slightly concerned by the intermittent nature of this (about three in four boots) that it could be a hardware fault. Any thoughts? Richard -- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Richard Lewis j: ironchicken(a)jabber.earth.li @: lewisrichard http://www.richardlewis.me.uk/ -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

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[ALUG Announce] ALUG Norwich Pub Meet Thursday 10th September
by Viperfang 07 Sep '15

07 Sep '15

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, 10th September 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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Coding a script
by Chris Walker 07 Sep '15

07 Sep '15

Hello, Can anybody help me please with some coding of a script? I regularly download mp3 files using get_iplayer which I then play in my Humax set top box. I find the Humax will display an image for the file if the image is embedded within the mp3 file. So I wrote a script to go through a folder and add the relevant image file. Here's my script :- for FILE in *.mp3 do bname=$(basename "$FILE") extension="${bname##*.}" filenamewoext="${bname%.*}" imagefile="${filenamewoext}.png" echo adding cover image ... eyeD3 --add-image $imagefile:FRONT_COVER:Picture "$FILE" echo Stripping any version 1 tags id3v2 --delete-v1 "$FILE" # Now for a tidy up and delete the original image file # search and add image img=$(id3v2 -l "$FILE" | grep -i "APIC") if $img =""; then echo "Adding the image failed" exit 1 else rm -f $imagefile fi done The problem comes in the tidy up section. I don't want to delete the image file if adding it has failed but even though I'm getting an error "mp3image.sh: line 47: APIC: command not found", the image is still being deleted. I've tried various ways of writing this code and all have failed. Writing code is far from my strong point so would appreciate some pointers as to where I'm going wrong particularly since if I type out the img=.. command in a console, it seems to work and produces a line like this :- APIC (Attached picture): (Picture)[, 3]: image/png, 58900 bytes so adding the image did work. -- __ __| |_ __ __ .----------------------------------------------. / _/ _` \ V V / | mailto:alug_cdw@the-walker-household.co.uk | \__\__,_|\_/\_/ |______________________________________________|

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Anyone know how to change user on Raspberry Pi GUI login?
by Chris Green 06 Sep '15

06 Sep '15

As per the subject. I have a Raspberry Pi with the latest raspbian installed. I've told it to run the GUI at boot. I want to change the user that it boots into, i.e. I don't want it to boot into the default user 'pi'. How does one do this? Google searching brought up all sorts of things about changing the pi login but not what I wanted to do. -- Chris Green

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hosts.deny
by steve-ALUG＠hst.me.uk 05 Sep '15

05 Sep '15

Hi y’all! Could someone enlighten me about hosts.allow & hosts.deny please? I was reading up on linux networking, and it said I should consider the contents of these files. So networking aside, I've read up a bit and am a lot confused. As far as I can find, 1) if there's an match in hosts.allow an address is allowed to contact the machine. 2) if no match in 1), then if there's a match in hosts.deny, then the address is not allowed to contact the machine 3) if no match in 1 or 2, then the address is allowed to contact the machine. Is this right so far? If so, what's typically in hosts.deny? I ask because I've obviously edited this in the past - I have a vague recollection of doing it because I couldn't get anything working and I just stripped it all out - I know - a very very bad idea. All I've got in there is: ALL: ALL: ::1 As far as I can figure out, the first line, ALL: would do nothing. ALL: ::1 I think would block all IPV6 addresses from contacting. Is my interpretation of the above right? What's typically in the hosts.deny for a server? If it's set up to block by default, then what should I enable? Is it sufficient to use netstat to work out what's listening for a conversation and just allow these things if I think they should be allowed. If so what's the correct use of netstat to find out? If I have things running as cron jobs rather than as a daemon to check things, do I have to specifically allow these to contact the outside world, or is hosts.allow/deny just for daemons? Lastly, does this work like a firewall? As I have firewall already set up, is it a good idea to spend time on hosts.allow/deny as well? Any advice appreciated muchly! Steve

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