Wurmd move from Google code to Github

Just in case anyone besides me would actually be using it: I've moved wurmd from Google Code, which has been deprecated for quite some time, to Github. https://github.com/timdingo/wurmd.

On ecryptfs and ssh public key authentication.

I'm using an Ubuntu (not by choice, mind you) box to compile stuff on, which I've set up with ecryptfs to encrypt my user's home directory.
It's a headless box so most of the stuff I do on it is over SSH and I've been really annoyed to learn ecryptfs, by default,  auto-unmounts the user's home directly every time the SSH session disconnects.
Why, you ask? Because it breaks public key authentication aka 'passwordless login'.
Turns out ecryptfs, by default, needs the user's login password to decrypt the volume, which it then mounts so all is good as long as one's using a password based login procedure.
Anyways: a reasonable workaround (as there's no fixing this design issue), as long as the box doesn't shutdown too often, that is, is to not allow the volume to unmount every time the working session is closed:

• Supply the password once over SSH, which auto-mounts the volume
• Remove the ~/.ecryptfs/auto-umount file
• Done

On Debian's init process

Are you tired of badly written, complex, buggy and generally shitty init systems on Debian based systems?
Do you wonder what certain Debian developers have been smoking lately?
Do you think upstart, systemd and the likes need to stay the fuck away from your otherwise pretty stable Debian systems and do you long for the simpler SysV days?
Yeh, me too.

apt-get install sysvinit systemd-

or

apt-get install sysvinit upstart-

takes care of it.
That's all.

Bancontact mobile application with a Belgian Keytrade account

It took some time to get it working; if the 'activation' step in the mobile application keeps failing, do this:
Log into the Keytrade web site and go to 'Cards' -> 'Card Security' -> 'Activate Card for Online Payments'.
That's it.

Screenshot because it's fancy:

Unsetting a trap

Quick one: catching a trap in bash is fairly easy with bash' trap command (search for 'trap \[' in bash' man page) but how to clear a set one?
It's in the man page, of course, but who reads those, right? I'm betting the answer is bound to be found on some blog through Google in 0.76 seconds flat ;)

"If arg is absent (and there is a single sigspec) or -, each specified signal is reset to its original disposition (the value it had upon entrance to the shell)."

So it turns out it's fairly simple and this demonstrates it:

root@mgmtsrv:~# cat test.sh
#!/bin/bash
trap 'echo TRAPPED!; break' SIGINT
while [ True ]; do
        sleep 1
done
echo 'end of script'
exit 0
root@mgmtsrv:~# ./test.sh
^CTRAPPED!
end of script
root@mgmtsrv:~#

Now, let's unset the trap:

root@mgmtsrv:~# cat test.sh
#!/bin/bash
trap 'echo TRAPPED!; break' SIGINT
while [ True ]; do
        sleep 1
done
trap - SIGINT
while [ True ]; do
        sleep 1
done
echo 'end of script'
exit 0
root@mgmtsrv:~# ./test.sh
^CTRAPPED!
^C
root@mgmtsrv:~#

So, in short: the 'trap - SIGINT' line clears the set trap :)

On loopback device creation

I was having some problems with loop back device creating & almost immediately detaching; it seems sometimes a kernel thread holds on to the device and the detach fails.
I decided to have a look what's going on so I created a script which automates the creation, attaching and detaching of loopback devices:

# ./test.sh

Creating sparse 4TB file: Done
----START----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
----NEXT PASS----
Loopback devices currently in use:
/dev/loop0
Checking for free loopback device: /dev/loop1
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
----NEXT PASS----
Loopback devices currently in use:
/dev/loop0
/dev/loop1
Checking for free loopback device: /dev/loop2
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
----NEXT PASS----
Loopback devices currently in use:
/dev/loop0
/dev/loop1
/dev/loop2
Checking for free loopback device: /dev/loop3
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
----NEXT PASS----
Loopback devices currently in use:
/dev/loop0
/dev/loop1
/dev/loop2
/dev/loop3
Checking for free loopback device: /dev/loop4
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
----NEXT PASS----
Loopback devices currently in use:
/dev/loop0
/dev/loop1
/dev/loop2
/dev/loop3
/dev/loop4
Checking for free loopback device: /dev/loop5
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
----NEXT PASS----
Loopback devices currently in use:
/dev/loop0
/dev/loop1
/dev/loop2
/dev/loop3
/dev/loop4
/dev/loop5
Checking for free loopback device: /dev/loop6
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
----NEXT PASS----
Loopback devices currently in use:
/dev/loop0
/dev/loop1
/dev/loop2
/dev/loop3
/dev/loop4
/dev/loop5
/dev/loop6
Checking for free loopback device: /dev/loop7
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
----NEXT PASS----
Loopback devices currently in use:
/dev/loop0
/dev/loop1
/dev/loop2
/dev/loop3
/dev/loop4
/dev/loop5
/dev/loop6
/dev/loop7
Checking for free loopback device: losetup: could not find any free loop device
Exiting, couldn't find any free device any more.

So if done fast enough the pool quickly gets depleted as giving back (detaching) the device fails. A second or so later it might work, though. But let's test how much time exactly is needed to free the device? I modified the script to keep trying to detach/free the loopback device and see what happens:

Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 4 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 2 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 6 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 1 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 3 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 3 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.

Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 2 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 3 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 2 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 4 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 4 tries.
----NEXT PASS----
Loopback devices currently in use:

Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 1 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 5 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 10 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 2 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 4 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 4 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 3 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
Loopback device broken down after 0 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 4 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 3 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 2 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
Loopback device broken down after 0 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 1 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 3 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 2 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 1 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 2 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 1 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
Loopback device broken down after 1 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: ^C

So it varies. The device might get released instantaneously, but that doesn't happen too often, or it might take 10 consecutive tries. Let's see if allowing half a second's worth of pause in between creating and detaching fix the problem,

# ./test.sh
Creating sparse 4TB file: Done
----START----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0.5 seconds.
Breaking down loopback device:
Loopback device broken down after 0 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0.5 seconds.
Breaking down loopback device:
Loopback device broken down after 0 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0.5 seconds.
Breaking down loopback device:
Loopback device broken down after 0 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0.5 seconds.
Breaking down loopback device:
Loopback device broken down after 0 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0.5 seconds.

^C

It does, but what's holding on to the device exactly? I modified the script again to look up the did in the process table. This takes time of course, so the detaching phase took less tries to complete:

# ./test.sh
Creating sparse 4TB file: Done
----START----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
root     25417  0.0  0.0      0     0 ?        S<   13:25   0:00 [loop0]
Loopback device broken down after 1 tries.
----NEXT PASS----
Loopback devices currently in use:
Checking for free loopback device: /dev/loop0
Setting up loopback device: Done
Sleeping for 0 seconds.
Breaking down loopback device:
loop: can't delete device /dev/loop0: Device or resource busy
root     25437  0.0  0.0      0     0 ?        S<   13:25   0:00 [loop0]
Loopback device broken down after 1 tries.
----NEXT PASS----
Loopback devices currently in use:
^C

Right, so it's Linux that's holding on to it and I'm not sure if I like this behavior. I realize losetup can only request Linux to free up the device and it does cleanly report a 'Device or resource busy' but I don't understand why it just doesn't wait a bit until the resource is cleared from the kernel, or at least provides the option to the user to do so. I thought about pathing losetup but now I can't be bothered anymore, so I'm just putting it out there :)

On bypassing mdadm's interactive mode

So I wanted mdadm to not go interactive, ever, but instead just bail out whenever something happens it doesn't understand; you'd think the developers would have thought of that, right? Turns out they haven't.
The 'fix' is easy enough though: pipe /bin/false through mdadm by default so it'll get a 'false' every time it would be looking for user input; effectively making it bail out whenever something's off:

alias mdadm="/bin/false | /sbin/mdadm"