Make PDF small with GS

With this trick you can make your PDF smaller even 10x with no noticable picture quality loss :-)

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/screen -dNOPAUSE -dBATCH  -dQUIET -dDownsampleColorImages=true -dColorImageResolution=200 -dColorImageDownsampleType=/Bicubic -sOutputFile=output.pdf input.pdf

Xilinx USB JTAG Platform Cable Vivado Linux

If you work with Xilnx Vivado Design Suite [1] for FPGA development using USB JTAG interface such as Xilinx USB Platform Cable [2] or its cheaper clone from WaveShare [3], everything seems to be connected properly, but it cannot find the Target for programming, you probably need to perform drivers setup manually [4]. Error message looks like this:

ERROR: [Labtoolstcl 44-494] There is no active target available for server at localhost.
Targets(s) ", jsn3" may be locked by another hw_server.

Error message may indicate that another instance of hw_server is running in the background but that is not the case. Check your drivers first [4]. Some hints:

  • Run as root and be careful as this will modify your OS.
  • Install script location is Vivado/2020.2/data/xicom/cable_drivers/lin64/install_script/install_drivers.
  • Platform Cable USB interface is pcusb.
  • Make sure UDEV rules are installed in /etc/udev/rules.d/ (i.e. 52-xilinx-pcusb.rules file).
  • After drivers are set up remember to restart UDEV with service udev restart command and re-attach your USB JTAG cable.


Why Linux Sux?

Imagine you have a disk full of your precious data that you want to mount to a new Ubuntu Linux system and add user to match the existing home directory.

# adduser user
Adding user `user' ...
Adding new group `user' (1000) ...
Adding new user `user' (1000) with group `user' ...
Creating home directory `/home/user' ...
Stopped: Couldn't create home directory `/home/user': File exists.

Removing directory `/home/user' ...
Removing user `user' ...
Removing group `user' ...
groupdel: group 'user' does not exist
adduser: `groupdel user' returned error code 6. Exiting.

Now you can say your all precious data goodbye. No questions asked. Core Linux utility adduser just found your existing data and erased them without even asking. The years is 2021 (30 years since Linux was created).

This is why for over 15 years I am only working with BSD Operating Systems [1] [2] [3] [4]. Its Open-Source with long-term maintenance and self-compatibility in mind.  BSD license is even more liberal than GPL for your products [5]. You should try BSD too :-)


Synaptics TouchPad on Panasonic CF-MX4

This wulf7 [1] is a really nice guy that helped me run full featured Synaptics TouchPad with FreeBSD on Panasonic Toughbook CF-MX4 [2][3]. Now it works for moused and libinput with all multitouch gestures like two or three finger scroll, scale, etc! The problem was in detection mechanism as device is connected over multiplexer with both PS/2 and SMBus but multitouch works only over SMBus. Although fix requires change and rebuild of FreeBSD Kernel I hope it gets quickly to the upstream [4]. I had a chance to exercise building whole FreeBSD distribution into the USB memstick image, so I could test driver fix on a target computer without even touching its hard drive contents :-)

/* psm has a special support for GenMouse + SynTouchpad combination */
if (active_ports_count >= 2) {
    for (port = 0; port < KBDC_AUX_MUX_NUM_PORTS; port++) {

That 2 above had to be changed into 1 in /usr/src/sys/dev/atkbdc/psm.c. Nice? That’s what I call a one-bit-fix :-)

In addition, when you work with Synaptics Touchpad in Xorg and you want to use its all features like tap-to-click, natural (swapped) two finger scroll, two and three finger gestures, don’t use moused,xmodmap, or xinput as this will produce inconsistent behavior in applications based on different toolkits (i.e. GTK will scroll up while Qt will scroll down etc), instead use the new way of input based on libinput and modify MatchIsTouchpad section of /usr/local/share/X11/xorg.conf.d/40-libinput.conf like:

Section "InputClass"
        Identifier "libinput touchpad catchall"
        MatchIsTouchpad "on"
        MatchDevicePath "/dev/input/event5"
        Option "NaturalScrolling" "on"
        Option "Tapping" "on"
        Option "ClickMethod" "clickfinger"
        Driver "libinput"


Disable Comments in WordPress

You can disable comments for existing posts using Bulk Edit, but this is not possible for existing media files. You can do both with a single SQL command :

UPDATE wp_your_table_with_posts SET comment_status = 'closed';

You can disable comments for all new posts either by hand as administrator unchecking Settings / Discussion / Allow people to submit comments on new posts, or using SQL command:

UPDATE wp_your_table_with_options SET option_value = NULL WHERE option_name = 'default_comment_status';

LimeSuite on FreeBSD

I have ported LimeSuite [1] to FreeBSD [2]. You can now work with LimeSDR [3] / LimeSDR-Mini [4] and others on my favourite OS. Please visit MyriadRF [5] for various radio inspirations. Have fun! :-)


Mounting external ZFS volume

If you need to perform a data recovery from an external ZFS [zfs] volume you may find those hinds helpful:

  1. Attach encrypted partition where ZFS pool resides with:
    geli attach /dev/your_device_partition
  2. Import ZFS pool at given mountpoint (/mnt/zfs):
    zpool import -af -R /mnt/zfs
  3. Modify mount point location for a given dataset that may have mountpoint set to none what marks it as no mount (note this mountpoint will append to parent mount point location):
    zfs set mountpoint=ROOT zroot/ROOT/default
  4. Mount and mount all pool datasets:
    zfs mount -a
    zfs umount -a
  5. Mount/umount given dataset:
    zfs mount zroot/ROOT/default
  6. You can verify if your ZFS pool is active with:
    zpool status
  7. You can see what ZFS datasets are available with mount points with:
    zfs list


macOS Virtual Audio SoundFlower Loopback

SoundFlower [1] is amazing Free and Open-Source extension to macOS BSD that allows you to create Virtual Audio Device in order to Route and Record Applications Audio. This is especially important for activities like Online Streaming and Presentation/Lectures Recording.

If you need more advanced Audio Routing with a nice GUI and lots of options try Loopback [2] from RogueAmoeba [3].

Thank you for this amazing fork and keeping it Open-Source! :-)


Blender Player Python

If you encounter a problem with running Python [python] scripts on a “bare” Blender Player [blender], make sure that both PYTHONHOME and PYTHONPATH are set correctly to match your needs. You can also use native Blender python with a simple shell script:

export PYTHONHOME="/path/to/blender/python/"
/path/to/your/blenderplayer $@


Apple macOS 10.13 High Sierra Fail

Guys at Apple are either stoned or really working hard to make macOS as bad as Windows. macOS High Sierra (10.13) was probably designed by people that were really “high”. They removed TELNET utility that is second most valuable network testing utility after PING. Except for noticeable performance degradation glitches during video modeswitch and other failures macOS really gets close to Windows in its poor design decisions and obvious quality degradation for professional applications.. now I will hardly consider buying another overpriced MacMookPro..

Added GOBI2000 support to FreeBSD U3G

I have added support for Panasonic ToughBook CF-F9 U3G GOBI2000 to FreeBSD U3G kernel module [1]. I have added firmware for Panasonic CF-F9 and HP EliteBook 2740p along with gobi_loader updates [2] that are required for 3G modems to work.

At first U3G module will create /dev/cuaU0 interface for QDL firmware load, then after successful firmware load device will reload itself to a modem mode and U3G module will provide additional /dev/cuaU0.* nodes for operations (/dev/cuaU0.2 is the AT command intarface).

In order for this modem to work on FreeBSD you also need to tune some configutation files:

  • /etc/devd.conf:
    attach 100 {
     match "vendor" "0x04da";  #adjust your device VID
     match "product" "0x250e"; #adjust your device PID
     action "/usr/local/sbin/gobi_loader -2000 /dev/cuaU0 /boot/firmware/gobi/";
  • /etc/ppp/ppp.conf:
     set log Phase Chat LCP IPCP CCP tun command
     ident user-ppp VERSION
     set device /dev/cuaU0.2
     set phone *99\#
     set redial 5 10
     set speed 115200
               \"\" AT AT-OK-AT ATH OK ATZ OK ATE1Q0 OK \
               AT+CFUN=1 OK-AT-OK \
               AT+CPIN? READY-AT+CPIN=\"YOUR_PIN_HERE\"-OK \
               AT+CGDCONT=1,\\\"ip\\\",\\\"internet\\\" OK \
               \\dATDT\\T TIMEOUT 40 CONNECT"
     set timeout 20
     enable dns
     set ifaddr
     add default HISADDR

You now should be able to use your 3G modem connection with ppp -ddial, after you add your local user to the dialer group with pw groupmod dialer -m your_user_name. Remember to have U3G compiled in. Enjoy the Internets! :-)