Why Won’t My GIMP Python Plug-in Show Up Under Filters?

tl;dr: Did you put it in ~/.gimp-2.8/plug-ins and set the executable bit ?

It’s been a while since I developed a script to automate tasks in GIMP. I figured I would do one for the repetitive tasks for creating a custom YouTube Thumbnail (more on that later perhaps). But my script wasn’t showing up in the Filters menu.

I had found the preference for setting the directory: Edit ? Preferences ? Folders ? Plug-Ins (not that GIMP treats python as plug-ins, not scripts); with the default user folder being ~/.gimp-2.8/plug-ins. But the plug-in dind’t show up.

Restart GIMP. Still nothing.

Ask on IRC. Double check the documentation (always a good idea). Aha!

Scheme and Python plug-ins are readable text files. C-language and Python plug-in files must have permissions set to allow execution.

chmod +x myscript.py later, and it registered!

Hope this saves someone the twenty or thirty minutes it took me to find this out!

Invalid Security Token Issues

tl;dr: Having both AntiSpam Bee and Jetpack Comments causes this, disable one or other

While trying to leave a comment on here on a previous post, I got an error:

Invalid security token

Apparently, AntiSpam Bee and Jetpack Comments are not compatible. I’m not sure when Jetpack comments were enabled as I’ve had relatively recent comments/ I will see if I can find an antispam plugin that is compatible with Jetpack comments, or disable those.

My sincere apologies to anyone who has tried to comment and not been able to as a result!

[Fixed] No LED light on Logitech K750 Keyboard

K750 charging under a lamp

tl;dr: Use a combination of a bright light and the reset technique (off ? CAPSLOCK + some keys ? on)


A few years ago while on holiday in sunny SC — a lovely place to visit, incidentally — I took the opportunity to purchase a Logitech K750 keyboard. The K750 was is a ‘solar’ keyboard- no changeable batteries, only solar cells to power it. I had been frustrated by other keyboards which needed battery changes timetabled in accordance with Sod’s Law.

They keyboard got passed on to my folks and all was well. However, since my dad passed away my mum has not used the computer as much, and so the lights in that room haven’t been on. When I went to use the computer there recently the keyboard was completely dead. Not even the red ‘sad face’ LED would light even if held close to a light source, which would normally elicit some response.

Leaving the keyboard in a decent amount of ambient light for a few days seemed to do very little to help.

Revivifying a K750

Enter Nut and his Tech, wherein they describe the reset procedure:

1. Turn off the keyboard.
2. While holding onto CAPS lock, keep pressing a few keys for the next 5 or more seconds.
3. Turn on the keyboard.

I did the above and held the K750 very close to a fairly bright bulb, and the LEDs sprang to life!

First the green happy face when still next to the light, then the red unhappy face when I took it out of full illumination.

So it works, for now. I was even able to type from the next room over where it sits charging beneath a mini anglepoise-type lamp.

Rescuing a Truncated Recording Using ffmpeg

tl;dr: Well, it’s cheating because it’s not ‘rescuing’ what isn’t recorded, just retrieving and appending

Last night I played a few rounds of some cooperative gameplay with some good friends, and as usual I recorded the session for posterity.

Hans Volter's on fire and about to die
“Oh man, oh god!”, Hans is about to croak.

However, when looking over the file created, neither VLC nor ffmpeg could determine a duration. I used ffmpeg to create a new file (ffmpeg -i old.mkv -c copy new.mkv), and when it got to about the 1 hour 50 minute mark in the stream copy, it printed the following error:

invalid return value 0 for stream protocol
[matroska,webm @ 0x55eb60b609c0] Read error
Invalid return value 0 for stream protocol

It’s possible that I ran out of space during recording, so it behoves me to make sure my disks are more clear — hopefully the process of migrating to a combined fileserver will help there! — before I start recording.

Fortunately, I also stream to Twitch and so I could create a ‘highlight’ of the latter part of gameplay- about 45 minutes’ worth. The quality isn’t as good (max bitrate 3500kbit), but it’s better than nothing. So that it can be seamlessly appended, I decided to upscale the size from 720p to 1080p using ffmpeg:

$ ffmpeg -i ~/downloads/211006613-69819912-48eb80ad-009f-42d5-83aa-f68dda7b7612.mp4 -vf scale=1920x1080:flags=lanczos
-c:a copy -crf 20 -preset slow ~/mounts/storage/video/2017-12-19\ 22-04-59b.mkv

frame=105361 fps= 24 q=28.0 size= 2402802kB time=00:29:16.20 bitrate=11208.1kbits/s speed=0.408x

(Conversion in progress! Using -vf scale=1920x1080:flags=lanczos to scale and -crf 20 to ensure quality stays reasonable)

After that, it should be a simple matter of using the concat demuxer, assuming the files are similar enough (both are pixel format yuvj420p)– I previously had issues when trying to create an auto-highlighter/clip creator that minimised re-encoding.

For posterity!

[Fixed] MySQL: Table is marked as crashed and last (automatic?) repair failed (+ WordPress)

tl;dr: run myisamchk on the problematic table

I’ve run into the following error in my Apache error.log recently:

Table 'database.tablename' is marked as crashed and last (automatic?) repair failed

Fortunately the fix is simple: run myisamchk on the table which is marked as crashed:

$ sudo su
# service mysql stop
# cd /var/lib/mysql/databasename
# myisamchk -r tablename
MyISAM-table 'tablename' is not fixed because of errors
Try fixing it by using the --safe-recover (-o), the --force (-f)
 option or by not using the --quick (-q) flag
# myisamchk -r -o -f tablename
Data records: 107435
Found block that points outside data file at 16166832
# service mysql start

I’ve run into these errors before due to running out of disk space on the (admittedly tiny) VPS I had.

I also had this problem with a WordPress database able, causing the often-seen and unhelpfully terse:

Error establishing a database connection

Interestingly, this wasn’t getting bounced to error.log, and I had to use the WordPress database repair screen to track down which one needed the fix (which was the same myisamchk).

All sorted now!

[Solved] “Logical volume is used by another device”

tl;dr: use dmsetup remove before trying lvremove

Note: Volume group and logical volume names have been substituted here. I’m not entirely sure it’s necessary, but better safe than sorry. If following this, please use the names of your volume group[s] and logical volume[s]

I am in the process of combining fileserver information, and so I have been touching parts of the system not usually looked at in the normal case of day-to-day operations. For some reason, on one of my logical volumes I had created a partition table and added a partition. Of course, that worked normally so there was no reason to be aware of this — clearly I had blanked the fact that I did it at all not long after doing so — until recently.

The Problem

Logical volume vg/lv-old is used by another device.

After copying the data over to a new logical volume, I wanted to remove the now-unnecessary original logical volume that contained the partition. Easy, right?

# lvremove -v /dev/vg/lv-old
    DEGRADED MODE. Incomplete RAID LVs will be processed.
    Using logical volume(s) on command line
  Logical volume vg/lv-old is used by another device.

Okay, what’s using it? cat /proc/mounts reports that it isn’t mounted. lsof and fuser return nothing. Maybe retrying the command will work*… nope.

There are a bunch of posts around this, mostly saying “make sure it is umounted first”, or “try using -f with lvremove“. And the old favourite: “a reboot fixed it”.

Find Out device-mapper’s Mapping

Well, the culprit in this case seemed to be device-mapper creating a mapping which counted as ‘in-use’. Check for the mapping via:

# dmsetup info -c | grep old
vg-lv--old       253   9 L--w    1    2      1 LVM-6O3jLvI6ZR3fg6ZpMgTlkqAudvgkfphCyPcP8AwpU2H57VjVBNmFBpL

Find Out Mapped Device

Then use that to find out what is holding it:

$ ls -la /sys/dev/block/253\:9/holders

drwxr-xr-x 2 root root 0 Dec 12 01:07 .
drwxr-xr-x 8 root root 0 Dec 12 01:07 ..
lrwxrwxrwx 1 root root 0 Dec 12 01:07 dm-18 -> ../../dm-18

Remove Device (via `dmsetup remove`)

Then do a dmsetup remove on that device-mapper device:

# dmsetup remove /dev/dm-18

Retry `lvremove`

And you’re good to go with lvremove:

# lvremove -v /dev/vgraid6/lv-old
    DEGRADED MODE. Incomplete RAID LVs will be processed.
    Using logical volume(s) on command line
Do you really want to remove active logical volume lv-old? [y/n]: y
    Archiving volume group "vg" metadata (seqno 35).
    Removing vg-lv--old (253:9)
    Releasing logical volume "lv-old"
    Creating volume group backup "/etc/lvm/backup/vg" (seqno 36).
  Logical volume "lv-old" successfully removed

Bish bash bosh!


*: I’m not sure of the thought process behind “just try it again”.

I’m reminded of a short bit of Darrell Hammond’s stand up (paraphrased):

“You know that message you get when you dial the wrong number that tells you to ‘check you have the right number and dial again’? Well, women will check the number and try again. Men will try the same number, but this time we’ll push the buttons a ******** harder…”

[Solved] “Filesystem is already n blocks long. Nothing to do!”

tl;dr: if you’re sure you did everything right, use lsblk or parted (etc) to see if a partition table is present on your logical volume.

So I am in the process of merging the content of two fileservers, and had the need to extend a logical volume to accommodate some additional data. No problem- that’s one of the benefits of using LVM!

Except after resizing, I ran into a problem:

$ lvextend +150G /dev/vg/lvinquestion
$ resize2fs /dev/vg/lvinquestion
> The filesystem is already 268435200 (4k) blocks long. Nothing to do!

Wait, what? Aside from the fact I could have combined the comments by including the --resizefs option to lvextend, why was resize2fs complaining that there was “Nothing to do!”?

Fortunately SE Arquade user ToxicFrog had the answer:

@bertieb parted reports the partition size, not the filesystem size
If it’s a partitioned LV you need to resize the partition after expanding the VL

Ah, whoops! I’m not sure why I partitioned the LV (it only had one partition) but I must have done so.

lsblk confirmed the partition:

sdh                                8:112  0   2.7T  0 disk
??sdh1                             8:113  0   2.7T  0 part
  ??md1                            9:1    0  10.9T  0 raid6
    ??vg-lv                      253:9    0   1.2T  0 lvm
    ? ??vg-lv1                   253:18   0   1.1T  0 part

So, then what? Well, I used dd to copy the filesystem to a new logical volume, then extended that, and finally removed the original:

# dd if=/dev/dm-18 bs=1M | pv -s 1T |  dd of=/dev/vg/lv-new bs=1M
# lvextend --resizefs -L 1.15T /dev/vg/lv-new
# lvremove /dev/vg/lv
# lvrename vg lv-new lv

(pv was included to give a nice progress indicator, rather than faffing around with SIGUSR1)

And that was that. There was a slight problem with removing the original logical volume, but more on that later…

Virtual Multiblog and .htaccess

TLDR: RTFM (http://striderweb.com/wp-content/multiblog/multiblog-readme.htm#permalinks)

I had problems with permalinks and Virtual Multiblog (yet another linky), basically that for every wordpress instance I added I would have to add another set of permalink-related Apache Rewrite rules to prevent individual entries 404-ing. This was fragile and prone to failure. Fortunately, there is a Proper Way To Do It:

RewriteEngine On
RewriteCond %{REQUESTURI} (/blog|/news)?/
RewriteCond %{REQUEST
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . %1/index.php [L]


From the readme. Lovely.

[Solved] sshd Does Not Run At System Startup (Ubuntu)


  • sshd does not appear to start on system boot, but runs fine when started from a terminal with /etc/init.d/ssh start

Update Dec 2010: Thanks to Jeremie here. Change the following in /etc/init.d./ssh to stop sshd starting before the network is ready:


# Required-Start:       $remote_fs $syslog 


# Required-Start:       $remote_fs $syslog $network

Merci Jeremie!

Cause and Solution:

  • A ListenServer directive in /etc/ssh/sshd_config is making sshd attempt to listen on a not-yet extant address. Change the directive to ListenServer

(NB: if you don’t have an /etc/init.d/ssh, you can get one from here)

I had a problem with a machine I am using as a samba fileserver. It would seem that the sshd process was not running at startup, so I would have to log into Gnome and run /etc/init.d/ssh start manually, which was a pain in the arse.

A quick search turned nothing up, except “make sure openssh-server is installed”, which in my case it was. I was about to post to the Ubuntu forums, but first I had a quick look at the syslog (which sshd prints to), where I saw entries like the following:

Jun 27 13:18:56 hermes init: ssh main process (802) terminated with status 255
Jun 27 13:18:56 hermes init: ssh main process ended, respawning
Jun 27 13:18:56 hermes init: ssh main process (806) terminated with status 255
Jun 27 13:18:56 hermes init: ssh main process ended, respawning
Jun 27 13:18:56 hermes init: ssh main process (810) terminated with status 255
Jun 27 13:18:56 hermes init: ssh main process ended, respawning
Jun 27 13:18:56 hermes init: ssh main process (814) terminated with status 255
Jun 27 13:18:56 hermes init: ssh main process ended, respawning
Jun 27 13:18:56 hermes init: ssh main process (818) terminated with status 255
Jun 27 13:18:56 hermes init: ssh main process ended, respawning
Jun 27 13:18:56 hermes init: ssh main process (822) terminated with status 255
Jun 27 13:18:56 hermes init: ssh main process ended, respawning
Jun 27 13:18:56 hermes init: ssh main process (826) terminated with status 255
Jun 27 13:18:56 hermes init: ssh respawning too fast, stopped

My thinking is that sshd was trying to start up before the network interfaces were configured, which was causing it to fail as it had a ListenAddress directive in /etc/ssh/sshd_config.

Commenting out the specific ListenAddress directive and adding ListenAddress to let sshd listen on any address solved the problem. The fileserver has only 1 IP address anyway.