Fresh linux install not booting? Don’t get mad, get googling. February 24, 2009
Posted by andrewgdotcom in Linux.add a comment
The main hard drive in my shitebox HP media centre PC died over the weekend, taking with it a significant collection of TV episodes. That didn’t bother me too much, as I rarely rewatch old TV, but it also meant that I couldn’t download any new TV, and that’s just intolerable when BSG, Dollhouse and Terminator are all airing in the States on the same night. My first reaction was to install Linux on a semi-spare USB-connected hard disk. One copy of the Lenny installer on a USB key later, and a base system was up and configured on an unclean partition.*
First problem: the bios won’t boot from USB hard drives, even though it boots from flash drives without a second thought. And no, it won’t boot from FireWire either. So, out with the screwdriver and the disk is transplanted into the main machine where the dead HD had been futilely spinning and radiating heat.
Second problem: the replacement drive is PATA, not SATA, and the mobo only has one PATA port. Not a problem, I wasn’t using the LightScribe DVDR for anything anyway…
Third problem (and this was the killer): GRUB hangs at
GRUB Loading stage 1.5
GRUB loading, please wait...
No amount of reinstalling or reconfiguring seemed to help, and I spent quite some time on google trying to track down possible reasons. I even installed grub on a USB key to see what happened; it got as far as the boot menu, but hung immediately afterwards.
Thinking it may have been something to do with installing on an unclean filesystem, I partitioned out some free space on the same drive and started from scratch. This ended up exactly the same way, but with an added “Error 22″. Much swearing was done, some of it on Twitter, and I went to bed really late and really angry two nights in a row, because I had two fresh yet broken installs of Linux and still no Galactica.
Maybe the disk wasn’t LBA? I didn’t think it was that old, but anything was worth a shot. Firing up parted, I tried to move the big partition out of the first 1024 cylinders to make space for a tiny boot partition. Parted gave me “Unable to satisfy all constraints on the partition”, which I had never seen before. When googling for this error, I stumbled across the following:
Error: Unable to satisfy all constraints on the pa: msg#00059 gnu.parted.bugs
The line about cylinder boundary alignment tickled something in the back of my brain. So, I booted up once more using the trusty usb key, ran fdisk and sure enough the old unclean partition didn’t end on a cylinder boundary. Deleting it and recreating it with the same parameters jiggled it a few kb larger and lo! both copies of Linux were magically fixed.
* Can’t be deleting the old photographs now, can we?
How to manage mailman list membership using LDAP or Active Directory February 20, 2009
Posted by andrewgdotcom in Linux, email.add a comment
Run this perl script on your mailman server once an hour using cron. Replace MY_LDAP_SERVER etc. with your own configuration. Also, depending on your LDAP implementation you may need to use group or groupOfNames instead of posixGroup.
For each list you wish to manage, create an LDAP/AD group with the email attribute set to the full address of the mailing list. The script scans all groups under the BASE_DN for any with an email address ending in @MY.LIST.SERVER. It overwrites each list’s membership with that of the corresponding LDAP group (if such a group exists, otherwise it does nothing). Make sure there is only one group for each mailing list! Multiple domain names are not supported, but could be with only a little hacking.
#!/usr/bin/perl -w
use Net::LDAP;
# Connect to LDAP proxy and authenticate
$ldap = Net::LDAP->new('ldaps://MY_LDAP_SERVER') || die "Can't connect to server\n";
$mesg = $ldap->bind(
'MY_DN',
password => 'MY_PASSWORD'
) || die "Connected to server, but couldn't bind\n";
# search for interesting AD groups
$mesg = $ldap->search(
base => "MY_BASE_DN",
filter => "(&(objectClass=posixGroup))"
);
die "Search returned no interesting security groups\n" unless $mesg;
foreach $group ($mesg->entries) {
$list_email = $group->get_value("mail");
# For groups with emails of the form "*@MY.LIST.SERVER"
# Try to chop off the name of our list server. If we fail, it wasn't meant to be.
if($list_email && $list_email=~s/\@MY\.LIST\.SERVER$//) {
# get the membership list
@member_list = $group->get_value("uniqueMember");
die "Security group for list $list_email looks empty - PANIC!\n" unless @member_list;
# make a list of emails to pass to mailman
$member_emails = "";
foreach $member_dn (@member_list) {
$mesg2 = $ldap->search(
base => $member_dn,
filter => "(&(cn=*))",
scope => "base"
);
die "Couldn't locate entry $member_dn - PANIC!\n" unless $mesg2;
$member = $mesg2->entry(0);
$member_emails .= $member->get_value("cn") . " get_value("mail") . ">\n";
};
# now update the mailman list membership
# be verbose!
print "\nchanging $list_email\n";
open( PIPE, "|/var/mailman/bin/sync_members -w=yes -g=yes -a=yes -f - $list_email" )
|| die "Couldn't fork process! $!\n";
print PIPE $member_emails;
close PIPE;
};
};
Vuze+feedmytorrents.com, a match made in…? February 7, 2009
Posted by andrewgdotcom in A/V, Software, Web.Tags: feedmytorrents, rss, vuze
3 comments
Despite having played with Democracy Miro, I’m still rather attached to Azureus Vuze for one or two of its useful features*.
Being an addict of US scifi TV, I was excited to discover feedmytorrents.com, which provides vodcast RSS feeds for most current popular US shows, such as my current favourites BSG and Lost. The killer advantage over other RSS sources (such as the excellent EZTV) is that one can subscribe to a particular feed in Miro or Vuze and get precisely one copy of every episode of that show. No more remembering to search mininova to see if the new episode was up yet! This was exactly what I had been waiting for since discovering Democracy Miro’s channels system.**
Of course, it didn’t take long for the system to break. Vuze’s RSS FeedScanner plugin would display a new episode in the list but not start downloading, instead giving a constantly shifting error message: “Init” > “Scanning 1/64…” >>> “Scanning 39/64…” > “Init” (it never seemed to get past 39). This would eventually time out saying “No data”. This affliction would only affect those particular episodes that feedmytorrents had sourced from mininova, but not those from the pirate bay (easily distinguished by the torrent URL). There was nothing wrong with the torrent file itself, as I could right-click > copy link URL and paste it into firefox, which would happily download the torrent and open it in Vuze, the default application. But of course this completely defeated the seamless experience.
I searched on the Vuze forums and found several similar problems reported but few solutions. One suggestion was that the setting “Use URL as referer” might need to be turned off. Sure enough, this worked. For whatever reason, it seems that mininova doesn’t like the HTTP referer field to be set to the “URL”, whichever URL that may be (itself?). Turning this option off (thus sending no referer) didn’t seem to break piratebay torrents (and why should it: this is the behaviour when one types in a URL by hand), so I disabled it on all my feeds. This makes me ask two questions. 1: why isn’t this option off by default and 2: what the hell does the HTTP referer field have to do with it anyway?
* coughcoughtorcoughcough! Interestingly, the latest version (4.1) of Vuze has reskinned itself to look almost exactly like Miro…
** sorry guys, I don’t watch Rocketboom…
Do what I mean, dammit. Or, why being silently “helpful” is evil. January 8, 2009
Posted by andrewgdotcom in Mac, Ranting.3 comments
For the last three years (i.e. before Time Machine), I have been using rsync to make incremental backups to an external FireWire disk from my trusty iBook. Now, rsync does this by backing up into a fresh location each time and referring to the previous backup to check if any data can be de-duplicated, which it does by creating hard links.
rsync -a --link-dest=$PREVIOUS_BACKUP $SOURCE $NEW_BACKUP
A wrapper script is needed because rsync doesn’t do any rotation of the backup paths (mine preserves six previous backups, which is quite enough), but overall the solution is elegant – restoration from any given backup is just a cp -pR away, due to the transparent nature of hard links. However (and this is the important bit) rsync only de-duplicates when the source file is identical to its previous backup in every way, including metadata.
As time went on and my laptop drive started getting full, I found that the backup window was getting suspiciously long for an 80GB disk. But it was the lack of space that finally drove me to buy a bigger external drive (admittedly, backups aren’t the only thing taking up GB on my FireWire farm).
Finally I ripped apart the wrapper script and dug through the previous backups. Turns out that rsync wasn’t preserving all the metadata, specifically file ownership. Google, as ever, gave me the answer:
Official Google Mac Blog: User 99, Unknown
By default, OS X silently maps all file ownership on external HFS+ disks to a special user “unknown”, while pretending to the user that he still owns the files. This is a “feature” to prevent weird permissions problems when swapping external drives between machines. It is so low-level that not even root can override it – if you try as root to chown a file on an external HFS+ filesystem, it will silently do nothing.
The upshot is that rsync didn’t believe that any backed-up files were identical to their originals, and so didn’t de-duplicate anything. Instead of six lean incrementals, I have six wasteful bulk backups, some of them incomplete because I ran out of backup window. And all the file ownerships have been lost, so a system restore would have failed spectacularly – if I had been foolish enough to try.
You can turn off this behaviour for any given disk (Finder>Drive>right-click>Get Info>uncheck “Ignore ownership…”), but it’s a bit late now.
The history meme April 16, 2008
Posted by andrewgdotcom in Linux, Mac, Software.add a comment
Spreading the meme…
serenity:~ andrewg$ history | awk ‘{a[$2]++} END {for(i in a)print a[i] ” ” i}’ | sort -rn | head -10
108 telnet
63 rscreen
43 ping
24 sudo
24 ssh
20 host
16 scp
16 more
14 ls
13 xdvi
Hm. I seem to be using the command line mainly as a gateway into remote systems – which reflects my average working day. The stray ‘xdvi’ is due to my recent heavy use of TextMate to write a paper in LaTeX. Not sure why I’ve been using sudo so much on my Mac though.
Similarly, on my work Linux laptop:
andgal@nbgal185:~$ history | awk ‘{a[$2]++} END {for(i in a)print a[i] ” ” i}’ | sort -rn | head -10
68 rscreen
52 ping
45 host
36 sudo
35 rdesktop
32 xrandr
21 startmenu
20 ssh
18 ifconfig
15 telnet
rscreen is merely a wrapper for ssh:
function rscreen() { /usr/bin/ssh -t $1 ’screen -dr || /usr/bin/screen || /bin/bash’; }
and startmenu is a cool but dodgy hack to get into my windows virtual machine:
alias startmenu=’nohup rdesktop -A -s “c:\program files\seamlessrdp\seamlessrdpshell.exe explorer.exe” 192.168.185.128 -u andgal -p xxxxxxxx&
xrandr reflects the fact that I have to configure my dual-screen setup by hand after each boot under Ubuntu 7.10, as the GUI configurator just Doesn’t Work. I had to test this many many times. Apparently the latest Ubuntu beta fixes most of these problems.
Widefox April 1, 2008
Posted by andrewgdotcom in Software, Web.Tags: google maps, mozilla, tabs
1 comment so far
I’m a Firefox user, but I used to like Opera back in the days before Firefox was available. I changed over once I discovered TabMixPlus and All-In-One Gestures, which collectively replicated most of Opera’s cool features – all except side-docked tabs, which doesn’t seem to be available in Opera any more either.
There are far too many things which like to dock with the top or bottom of my screen. Given that I use a Mac, I already have an extra menu bar to start with anyway. Computer screens are increasingly in widescreen aspect ratio, but documents read best in portrait mode. This is why most blog software (including this one) puts links and metadata at the side of the page rather than at the top, but there are still webapps out there (Google Maps being one of the worst offenders) that have a huge, wasteful banner across the top of the page.
So imagine my joy today when I found this Firefox chrome CSS hack:
The dropdown menu placement doesn’t match the tab bar location, but that’s a minor problem. I can now see Google Maps in a slightly less letterboxy format. Woohoo.
Particle smasher ‘not a threat to the Earth’ – opinion – 28 March 2008 – New Scientist March 29, 2008
Posted by andrewgdotcom in Ranting.add a comment
A group in the US has taken out a lawsuit to try to prevent the Large Hadron Collider starting up. Why? Because it might destroy the earth, of course.
Particle smasher ‘not a threat to the Earth’ – opinion – 28 March 2008 – New Scientist
I hate to say it, but that’s what happens when popular science magazines blindly give credence to any old nonsense wittered by someone with a science degree. Planet-eating particles, my arse.
The ActiveX effect February 18, 2008
Posted by andrewgdotcom in Microsoft, Ranting, Web.4 comments
In my current job, Microsoft Sharepoint rules. The decision was made long before my time to employ it as the common document repository, and for most people it works reasonably well. I have to force myself to use it though, and I can distil the reasons down to one root cause: ActiveX controls.
In its vanilla, static-page form, Sharepoint is barely functional. It takes a minimum of four clicks (open, edit, modify, save) to change a radio-button option. Checking files in and out is a pain – it’s easier to just overwrite. And I’ve never managed to attach a file to a list entry. To make it really useable, you need to run IE.
Oh wait, you’re using a Mac. Well you can just piss off then.
It’s interesting that Microsoft poured thousands of programmer-hours into developing an alternative to JavaScript and not one of the other browsers makes any attempt to support the resulting spec – this in a world of Mono, Samba, Moonlight and OpenOffice. MS dropped IE support on the Mac but keep pushing ActiveX in their server products. I’m no expert, but the only thing I see ActiveX doing that JS can’t is installing software updates without bothering the user with dialog boxes. Which is a good indication of why nobody else will touch it with a barge pole.
The problem is not confined to Sharepoint. The motivation for this post was finding that Microsoft’s certificate management server requires scripting to be turned on (it doesn’t say what sort of scripting, but it isn’t JS) in order to process a simple form that could have been written in 1995. In this case there was no option but to boot up the VM and use IE.
So what to do? Struggle manfully with Sharepoint’s prehistoric static interface or retreat into the VM, cut off from my usual editing suite – Office X for Mac. Somebody somewhere is no doubt enjoying this juicy irony. But it’s not me.
Topology November 27, 2007
Posted by andrewgdotcom in Maths.add a comment
I was reading up on some of the background to Garrett Lisi’s interesting new paper when I came across this gem via Sabine Hossenfelder’s blog.
Outside In – how to turn a sphere inside out
If that makes your brain melt, Bee also has some more frivolous stuff.
Galway Linux installfest, Sat 17th Nov November 13, 2007
Posted by andrewgdotcom in Linux.1 comment so far
Galway LUG is organising a Linux installfest on Saturday 17th from 10am-noon in the DERI building, Lower Dangan (map). This is a chance for you to bring along your old laptop/desktop and give it new purpose in life! If you have thought about trying Linux, but haven’t yet summoned up the courage, here is your chance to get some hands-on help. We will have several experienced users on hand to help you select, install and configure your first Linux.
A word of warning: if you have data on your hard drive, please BACK IT UP before bringing your machine. Galway LUG and its volunteers cannot be held responsible for loss of data. It is your responsibility to have current backups.
See you there!
