Mar 292018
 

For some reason when I look at RADIUS packet captures using Wireshark, the attribute Operator_Name is instead interpreted as Multi-Link-Flag (an integer rather than a string). I’m not sure what this is, but it is much more useful to me to be able to see the Operator_Name properly – and for example, filter on it.

It turns out this is easy to “fix” (if it is a fix) :-

  1. Find the file radius/dictionary.usr (mine was /usr/share/wireshark/radius/dictionary.usr)
  2. Edit that file, and comment out three lines containing “Multi-Link-Flag” which in my case appeared like :-
    1. ATTRIBUTE Multi-Link-Flag 126 integer
    2. VALUE Multi-Link-Flag True 1
    3. VALUE Multi-Link-Flag False 0
  3. Save the modified file.

After a restart, Wireshark now understands it.

It is possible that later versions of Wireshark have fixed this, or not – it is possible that the bug is down to whoever assigned RADIUS attribute codes!

Mar 252018
 

It seems likely that the company Cambridge Analytica paid Facebook for access to data and using it’s access, downloaded as much data as possible for nefarious purposes. Nobody should be that surprised at this.

Facebook does not host an enormously expensive social network just because it is fun; it does it to make money. It probably does this primarily through advertising, but selling access to social network data is always going to take place.

And from time to time, scandals when companies like Cambridge Analytica are going to take place. At which point Facebook will protest saying that it didn’t realise that the associated firm was doing such naughty things. And once the story drops out of the news, Facebook will carry on leaking data.

As the saying goes: “If you are not paying for it, you are the product.”

In the end, the only solution to something like this, is to produce some kind of peer-to-peer application that is as easy to use as Facebook, uses strong end-to-end encryption, and keeps our data private to those people and groups we choose to share it with.

The Hole

Mar 092018
 

One of the things that annoys me about pagers such as lessmore, most, etc. is that they are dumb in the sense that they cannot detect the format of the text file they are displaying. For example, all of a sudden I find myself reading lots of markdown-formatted files, and I find myself using most to display it – never remembering that it is mdv I want.

As it happens, when I invoke a pager at the shell prompt, I typically use an alias (page or pg) to invoke a preferred pager, and by extending this functionality into a function I can start to approach what I want :-

function extension {
  printf "%s\n" ${${argv/*\./}:l}
}

function page {
 if [[ -z $argv ]]
 then
   $PAGER
 else
   case $(extension $argv) in
     "md")
       mdv -A $argv | $PAGER
       ;;
     "man")
       groff -m mandoc -Tutf8 $argv | $PAGER
       ;;
     *)
       $PAGER $argv
       ;;
     esac
   fi
}

(the function “extension” has had a quick bug fix applied to smash the filename extension to lowercase)

Of course there are undoubtedly umpteen errors in that, and probably better ways to do it too. And it won’t work properly on its own ($PAGER hasn’t been set).

But it’s the start of something I can use to display all sorts of text files in a terminal window without having to remember all those commands. But as for ‘intelligent’, nope it’s not that – just a bit smarter than the average pager.

Feb 082018
 

Some time ago, I wrote about using new (for the time) partition tables to create a memory stick with 100 partitions; each with a mountable file system on. And decided the time was right to have another look to see if things have improved … or degraded. After all, things have moved on, and everything has been updated.

I also improved the creation script slightly :-

#!/bin/zsh

disk=/dev/sdb

parted $disk mklabel gpt
for x in {1..99}     
do
  echo Partition: $x
  parted -s $disk mkpart FAT $(($x * 100)) $((x * 100 + 99))
  sleep 0.2
  mkfs -t vfat -n DOOM${x} ${disk}${x} 
  sleep 0.2
done

And I used a zsh-ism – so shoot me.

The script ran fairly well, but :-

  1. The load average shot up through the roof as copies of systemd-udevd started, worked, and closed.
  2. Strangely the links in /dev/disk/by-label (and presumably elsewhere) kept disappearing and re-appearing. As if on each partition change to the disk, all of the disk’s devices were removed and re-created. This is probably not dangerous, but harmful to performance.
  3. Given that I used sleep within my script, it is hard to criticise performance, but it did seem slow. However this is not an area worth optimising for.
  4. Unlike last time, Linux did not refuse to create any file systems.

Now onto trying to stick the memory stick of doom into various systems…

Ubuntu 17.10

This was of course the machine I ran the script on initially.

This did not go so well, with the machine initially freezing momentarily (although it is a cheap and nasty laptop), apparently silently refusing to mount half the file systems, and “Files” (or Nautilus) getting wedged at 100% processor usage.

After some 10 minutes, Nautilus was still stuck with no signs of making any progress.

After I lost patience and restarted “Files”, it came up okay showing the mounted file systems and showing the file systems it had failed to mount. On one occasion the additional file systems were shown as unmounted (and could be mounted) and on another they were shown as mounted (even though they weren’t).

So both “Files” gets a thumb down for getting stuck, and whatever else gets a thumb down for trying and failing (silently) to mount all the file systems.

This is definitely a serious degradation from the previous try, although probably GNOME-specific rather than Linux-specific. Especially as a later mounted all the file systems from the command-line on a different system without an issue.

Windows 10

Windows 10 became unusually sluggish, although it may have been in the mysterious “we’ll run Windows update at the most inconvenient time possible” mode. It did attempt to mount the file systems, and failed miserably – it mounted the first set until it ran out of drive letters.

Which is just about understandable, as there aren’t 100 drive letters. However :-

  1. Where was the message saying “There are 100 partitions in this silly USB stick. You can see the first 22; additional ones can be mounted within folders if there is important data on them.”.
  2. Why is Windows still limiting itself with single letter device names? Okay it is what we’re used to, but when you run out of drive letters, start using the file system label – “DOOM99:”. Hell, I’d like all my removable disks treated that way under Windows.

As for the whole “ran out of drive letters, so don’t bother with the rest”, how many people are aware that drives can be mounted (as Unix does) in directories?

macOS 10.13 (OSX)

Oddly enough (but perhaps sensibly), macOS refused to have anything to do with the memory stick. Indeed it popped up a dialog suggesting initialising the disk, which is perhaps not particularly sensible with a disk that could contain data.

The “Disk Utility” happily showed the disk – increasing the size of the window inconveniently wide in the process – and happily indicated 99 partitions.

At the Terminal prompt, it was apparent that the operating system had created device files for each of the partitions, but for some reason wouldn’t mount them.

Summary

Inserting a “stick of doom” with 100 partitions on it into any machine is still a risky thing to do. It’s also a dumb thing to do, but something operating system developers should be doing.

Linux (or rather GNOME) performs significant worse this time around than previously, and my suspicions are that systemd is to blame.

But however bad Linux does, none of the operating systems actually do sensible things with the “stick of doom”. macOS arguably comes closest with refusing to have anything to do with the disk, but it also encourages you to reformat the disk without saying that it could be erasing data.

Ideally, a gooey would pop up a window listing the file system labels and ask you which you want to mount. That’s not even a bad idea for a more sensibly set up memory stick.

Pebble On Steel

Feb 022018
 

On occasions, I have run into issues where mounting a filesystem from /etc/fstab fails on a reboot because it depends on something else happening first. The easiest example to recall is when mounting a conventional filesystem constructed from a ZPool block device – the block device isn’t ready until ZFS has finished starting which often occurs after the filesystem mounts are attempted.

The fix is dead simple; just add the option “_netdev” to the options field in /etc/fstab and the problem is sorted :-

/dev/zvol/pool1/vol-splunk      /opt/splunk     ext2    noatime,_netdev         0 2

Yes the reason I am using a block device is that Splunk doesn’t support being installed on a ZFS filesystem.