Remote Desktop to Linux Box in Shop

 Using XRDP, I am able to do all my development from my office now:

Once temperatures rise, this will be much nicer than doing this in the garage.

Why Linux is not Replacing Windows Anytime Soon

I s pent most of my career using Unix for software development or being sys admin for a herdof Sun workstationx. Unix/Linux has many virtues.

A friend who is not technical has just switched from Windows 7 (don't laugh, he is moving his email from AOL after 36 years).. He wanted a regular backup of his files to a USB hard drive.

Okay, how hard can this be? Somewhere there is a program either GUI or shell-based that does this, right?  Not that I could find. After a lot steps that brought back memories:

1. Set up mount of USB drive in /etc/mount. What? HNo atomount or autodiscovery? You run lsblk to see what devices are attached, determine which is the USB drive, copy its 8 hexadecimal digit UUID and several other close to magic fields. (I started to remember what UID and GID mean as I fiddled.)

You rediscover that mount is a very picky program. How many spaces between parameters, Running sudo mount -a may not identify errors, just silently fail. How would it be to make a mount editor that prompts you for the parameters ands adds them to /etc/mount?

3. The backup script using rsync was fairly straightforward.

#!/bin/bash

# Mirror backup to USB drive (vfat friendly)




BACKUP_BASE="/mnt/usb-backup/Backups"

LOGFILE="$HOME/backup.log"




echo "$(date '+%Y-%m-%d %H:%M:%S') - Backup started" >> "$LOGFILE"




# Check if USB is mounted

if ! mount | grep -q " /mnt/usb-backup "; then

echo "$(date) - ERROR: USB not mounted at /mnt/usb-backup" >> "$LOGFILE"

echo "ERROR: Please run: sudo mount /mnt/usb-backup"

exit 1

fi




mkdir -p "$BACKUP_BASE"




# === Directories to mirror - Add more here if needed ===

declare -A DIRS=(

["/home/$(whoami)/Documents"]="$BACKUP_BASE/Documents"

["/home/$(whoami)/Pictures"]="$BACKUP_BASE/Pictures"

)




echo "$(date '+%Y-%m-%d %H:%M:%S') - Starting rsync mirror..." >> "$LOGFILE"




for src in "${!DIRS[@]}"; do

dest="${DIRS[$src]}"

if [ -d "$src" ]; then

echo "→ Mirroring $src" | tee -a "$LOGFILE"

mkdir -p "$dest"

rsync -aAX --delete --info=progress2,stats2 "$src/" "$dest/" >> "$LOGFILE" 2>&1

else

echo "Warning: $src not found" >> "$LOGFILE"

fi

done




echo "$(date '+%Y-%m-%d %H:%M:%S') - Backup completed successfully" >> "$LOGFILE"

echo "✅ Backup finished successfully!"

echo "Log saved to: $LOGFILE" 

Adding an entry to crontab was simpler than mount but it still screams for a tool to help you add an entry. Some of why Linux remains user-indifferent is that for a lot of geeks it is the same theory as stick shifts: "It keeps the riff-raff out." 

The Weirdness With LinuxCNC

I was was eventually able to install version 2.7.14.  I think the ISO was not written correctly first time.  Upgrading to latest version seems too hard. 2.7.14 is ancient history but it works.

I had saved my .emacs, .ddd, and .bashrc files along with all my programs and then restored them.  But lots of things stopped working.  The lisp commands in my .emacs file are not running.  make no longer works.

gcc  - -g -o mkcircle mkcircle.c -lm
gcc: error: -E or -x required when input is from standard input
make: *** [mkcircle] Error 1

Since when did gcc require these flags?

UPDATE: the compile problem was that I accidentally changed CFLAGS=-g to CFLAGS= -g.  That space confused accidentally pretty badly.

My emacs lisp commands are still confused.   The binding to compile command is not using directory from which emacs started.  I am getting close.

And linuxCNC has some setting for maximum Z wrong.

Frustrating

Yesterday, linuxCNC stopped running on the Dell Optiplex 960 desktop.   It hung the OC when I opened a file that has never previously caused problems.  After reboot, I tried to debug the program that created that file.  The ddd debugger (which is really cool) started failing to find C libraries.

Next, I attempted to use the Ubuntu Package Manager to reinstall linuxCNC.  This may have been a bit optimistic: this Debiab-based build has some odd real time kernel components in it.  It would no reinstall.  Nor could it uninstall and remove linuxCNC.

.

Next, I decided to start with the linuxCNC 2.9.2 ISO DVD to do a full reinstall.  No luck.  Even though that DVD turned out to be bad, the BIOS Diagnostics reported Spindle Error for the drive.  I found that a Dell brand DVD drive is available.   It should be here tomorrow  

Next: i burned a fresh linuxCNC 2.9.4 ISO and used a USB DVD drive.  It at least booted but failed part way through copying files as part of installation. 

Next: i found an antique version of linuxCNC (back when it was called EMC2) that came with the mill 15? years ago.  That booted and installed.  Alas it is a version so ancient that Package Manager told me to go away and look for something that did not use Roman numerals.   (I am exaggerating slightly.)

So next, linuxCNC 2.7.14 ISO, which i have installed on this PC back when the DVD drive still worked.  This DVD boots, but stops copying installation files part way through.   No useful error messages and it leaves the hard disk non-bootable. 

What a day!

WiFi LinuxCNC

 I have battled a little with my LinuxCNC PC somewhat randomly changing its IP address, even without a reboot.  This is odd because DHCP usually reserves the association for some period of time based on the original DHCP request.  (This is my memory of porting a DHCP server at a startup for which I worked.)

I finally broke down and fiddled with /etc/network/interfaces/ to tell it to go static.  No more fiddling with IP address in FileZilla!

Also, LinuxCNC is notoriously picky about WiFi cards and there is no  practical way to run Ethernet to the shop.  I finally found a 1300AC WiFi card that is plug'n'play a while back.  The data rate has never been impressive.  I suspect because line of sight from tower to router goes through the refrigerator.  I typically have been seeing 5.5 Mbps.  This is adequate for my needs but it seems absurdly slow.  So this afternoon, I thought, "What if I move it from the front of tower to the USB port at the rear.?  11 Mbps.  The WiFi came with an extension USB cable.  Using that and raising in the air gave a slight hint that performance might improve a few feet higher or east of the fridge.  I think I have a male USB-A to USB-A cable here somewhere.  If it a few feet longer, I may try it.

My cellphone in the same location gives 90 Mbps.  This WiFi adapter may just be a bit limited. 

Obscure Bash Question

 It has been almost 20 years since I made heavy use of Unix, but I vaguely recall a construct in some shell where you could 

ls {circle*|mkcircle*} 

and have it match every file of those two wildcard matches.  I cannot find that in any reference work.  Was that just an imagined capacity because I wanted it?

SMB

 I see no point battering my head against OpenSSH.  However, I have reached the point where:

 smbclient //192.168.4.42/linuxcnc -U clayton%mypassword

gives me access to the Windows directory. But

sudo mount -t cifs -o claytoncramer@192.168.4.42 /mnt/linuxcnc

 asks for the same password and rejects it.

Several syntax errors in the mount command.   Solved. I wish Linux utilities were a little more specific about where and what is the error. 

Then I discovered that I could not write in linuxcnc from Linux.   I verified permissions were wide open on Windows and 777 on linuxcnc.  It turns out the /etc/fstab entry needed file_mode=0777,dir_mode=0777 as well.  Before I forget all this, I need to reboot Linux and make sure it still works.

My Frustration With ChatGPT Continues

I have given it several programming problems that it asked me enough questions to solve. I requested a program to produce gCode to produce a particular hole pattern in a 6" high hexagon.  Itctook a couple tries to understand what I needed, but it managed.

Attempting to get it to make Windows 11 provided sftp server support remains beyond it.  After four hours fighting OPENSSH,  going in the same circles repeatedly,  I asked if there were any commercial or free sftp servers for Windows 11.  There were.  None of them actually work.  Each time one failed, it would suggest another that does not work.

I really cannot fault it with respect to Microsoft OpenSSH.  It is a very complex disaster with more layers of permission requirements for file access and user name and group than makes sense.   The previous way it kept trying to find some sftp server was very gratifying, but at some point, it needs to recognize that there seems to be no Windows 11 solution.  (Even attempting to run aside under Windows Subsystem for Linux was a failure.)

Two Hours With CHATGPT Trying to Get OpenSSH Server Working

No closer than when I started.   If you want to do something utterly vanilla with Windows 11, on your local PC, it works well. Anything even slightly unusual, such as using sftp to transfer files from Linux and it turns into a steaming pile at about Linux levels of knowledge.   At least getting an ftp server working under Linux is easy (or builtin?).

I wish Linux were adequately supported for various hardware and with adequate self-repair capabilities. 

Microsoft Cannot Leave Anything Alone That Works

The last I set up FileZilla to sftp files from Linux in the shop and Windows 11 PC, it was painless and symmetrical.   I could download from Windows to Linux and Linux to Windows.   

This time trying to set it up has been a pain.  FileZilla copies from Windows 11 to Linux without problems.   From Windows 11 to Linux, not so easy this time. 

I have to install OpenSSH in Windows.  I do not remember doing this.  If I did, the rest of the process (configuring OpenSSH, using whoami to get Microsoft user name and Microsoft password, we're not part of the process.   And it still does not open an sftp connection from the command line in Linux.

Strictly speaking,  I can live with only a one-way connection.   It is just annoying.  If only Linux were as well supported as Windows.

RCS Question

 Yes, I know, RCS is obsolete.  I should burn the time learning to use git.  But I am a single user and git is already lookimg daunting.  I spent much of my career using and maintaining RCS.

All the documents say that RCS's repository is in the RCS directory below current directory.  rcs ci -i filename puts nothing in RCS directory.  What am I doing wrong?

Never mind.  I found a simple git tutorial.

A Pleasant Surprise

 Windows Subsystem for Linux (WSL) is actually sufficiently Linux to run and install many linux commands such as gcc, make, and ddd.  This is not a port of Unix tools to Windows but apparently genuine Ubuntu Linux.

I battled endlessly trying to get VMWare and Oracle VirtualBox to run linuxCNC on my PC, so that I code stuff in the cool of the house before ftping it to the shop.  

This is sufficient.   I can code and debug in the house.  It would be nice to run linuxCNC for testing operation in the linuxCNC GUi, but this is good enough. 

Virtual Machines

I run linuxCNC (a Debian variant) in the shop.  There are times especially when it very hot out there thst I would prefer to debug programs inside.  At one time, under Windows 10, I used the VMWare virtual machine software to run linuxcnc on my Windows PC.

At some point this stopped working.  I was never able to get Oracle VirtualBox to do this.  The Windows 11 Hyper-V feature seemed to not work either.

I now see that Windows Subsystem for Linux gives this ability to run Linux variants under Windows 11.  This is good.   I can write software and run the CNC part as a simulation.   (There are some real-time aspects of linuxCNC that make it not work under any Windows VM.)  I can then use FileZilla to move the needed files to the shop PC.

 

UPDATE: Attempting to install linuxCNC under WSL was not easy.  This may require more help.

bash Number Comparison is Confusing

A program rel compares two numbers and returns -1 0 or 1 depending on less than, equal, or greater than compare of the two floating point numbers.

I am trying to use the resulting exit code to make a decision.   -1 turns into 255 as $?.

What is the if statement to see if $? Is 1?

UPDATE: It is simpler to write a C program.   Fortunately bash is similar enough to C that I was able to copy and do some replaces to change it to C.  It should also be easier to debug.

I have changed my strategy.   I am going to write of these in C from now on.

My first job (and what I did most of the time I was there) was maintaining a 6000 line csh script that did automated testing of the LaserJet firmware.  If there is any stronger argument for limiting scripts to 200 lines. I cannot imagine it.

Today's Bash Question

This should not be this hard. I want to do a while loop on the condition "$xstart  < $xend"

while [ "$xstart < $xend" ]

do

...

done

I know that to do a float compare, I need something like 

echo "$xstart > $xend" | bc -l 

returning a boolean.

Found it:

    while [ "$(bc <<< "$xstart < $xend")" == 1 ];

Bash Question

There seem to be no simple explanations that I can find.  All add more brackets and parentheses to accomplish what?

    if [[ ($yremaining+$millradius \> $yend) ]]; then

I want to see if yremaining + millradius is greater than yend.\

Conditional binary operator expected.

The answer seems to be

Corrected version (as text):

if (( yremaining + millradius > yend )); then

    echo "Condition met"

fi

I cannot believe how much I have forgotten.   My first three years at HP was maintaining, optimizing, and then factoring a 6000 line bash script.

If 6000 lines in one script sounds stupid,  yes it was. It was test tool that verified the functionality of the LaserJet firmware before we loaded into test mules.  Eventually, I factored it into several scripts each of which was still too large, but were at least comprehensible as to function.

This should not have been so hard.  Many good suggestions.  I decided to make a bash script that accepts two strings and returns an exit code (-1, 0, 1 for <,==,>).

 Of course, when you echo $?, because the exit code is returned as an unsigned byte it is 255.  This lets me do this test in multiple places with little pain.

#!/bin/bash
# rel: calculate <,==,> for two float strings
calculatedx=`echo $1 | bc -l`
calculatedy=`echo $2 | bc -l`
value=`echo "$1 < $2" | bc -l`
if [[ $value -eq 1 ]]; then
exit -1
fi
value=`echo "$1 > $2" | bc -l`
if [[ $value -eq 1 ]]; then
exit 1
fi
value=`echo "$1 ==  $2" | bc -l`
if [[ $value -eq 1 ]]; then
exit 0
fi

 

rel '20+.1' 21

echo $?

1

My efforts to get this working reliably in either bash or perl being unavailing, I wrote a program in C:

#include <stdio.h>
#include <float.h>
#include <stdlib.h>

int main (int argc, char* argv[])
{
  if ((argc >= 4) || (argc < 2))
{
  fprintf(stderr, "rel needs two arguments, both float\n");
  exit (4);
}
float arg1;
 if (1 != sscanf(argv[1], "%f", &arg1)) {
   printf("invalid argument %s\n",
      argv[1]);
  exit(4);
    };
float arg2;
 if (1 != sscanf(argv[2], "%f", &arg2)) {
  printf("invalid argument %s\n",
      argv[2]);
  exit(4);
  }
if (arg1 < arg2)
  {
    fprintf(stderr, "<\n");
    exit(-1);
  }
 else if (arg1 == arg2)
   {
   fprintf(stderr, "==\n");
   exit(0);
   }
 else
   {
     fprintf(stderr, ">\n");
     exit(1);
   }
}

Okay, the writes to stderr produce a flood of useless messages but I wanted to see what was happening.

Interesting Linux Discovery Over the Weekend

Yeah, I know, I am not the cool kid cause I use Windows 11 for almost everything.  But I do run the CNC version of Linux (based on what Linux?  I am not sure).  For some weeks now, it seemed as though my WiFi had stopped working.

The CNC machine is in the garage.  Range?  My cell phone can see it.  The icon shows bars but fast.com says that the servers cannot be reached.  I pulled the USB WiFi device, plugged it back in, rebooted, and in general took the obvious steps.

The other day, I tried Google and I received a date problem.  The PC thinks it is 2009, and Google disagreed.  After a few minutes reacquainting myself with the date command, everything runs again.

I had seen a message during boot about the system battery failed.  This is what keeps the system clock up to date when the machine is off.  At boot, the OS interrogates the system clock.  Linux and likely Windows then use NNTP (or NTP?  too long since I had to read RFCs for employment) to get a more accurate time to store in the system clock.  If that battery somewhere on the motherboard has failed the system clock defaults to its birthdate at the next boot.

Those of you who remember having to set the date and time each time you rebooted your PC appreciate this little complexity.

There is no urgency.  I do not reboot that PC very often.  I just need to pick a morning to find out where and what that battery is for this HP Optiplex and open it up.

Why Linux Does Not Replace Windows

 I just installed Linux Cinnamon dual boot on my old laptop and indeed it is very speedy compared to Windows 10.  But the TP-Link USB WiFi adapter is not recognized.  Okay, it is a year or two old, so I should not expect Linux to recognize it but searching the web for how to install drivers for it has been so far fruitless.  I am blogging through an Ethernet cable.  I understand sudo apt update etc. and roughly understand git's purpose, but I would not expect any non-techie to have a clue how to get WiFi working.

This seems to indicate that they are not available.

I had another clunkier TP-Link USB adapter which came right up.  It is not AC1300 but it works.

The AC1300 does not work in the Linux box in the workshop either.  LinuxCNC recognizes it as WiFi but that is as far as it goes.  It does not appear as though a/b/g/n work, much less ac.

Gcode Arcs

 I think that I am getting this, finally.

I started with th example and some graph paper.

%
g1 g20 g40 f500
g0 x0 y0 f500
g0 y1 f500
g0 y0 f500
g0 x-1 f500
g1 x1 f500
g1 x0
g1 y-1 f500
g0 x0 y1 f500

g2 x1 y0 i0 j-1 f500
g2 x0 y-1 i-1 j0 f500
g1 x0 y0 f250
m2
%

No, I am not cutting 2500 ipm.  That might work on air, who knows?  But the backplot feature of linuxCNC was taking forever.  I altered MAX_VELOCITY in the config file.  I am running linuxCNC in VirtualBox.

The first G2 made a 90 degree arc; the two g2 made another 90 degree arc.  If this does not seem that hard that it should have taken hours to figure out, you have more working brain cells than me.  The next step is making an arc that is only part of a 10" circle.

I am sure there is a way to do a screenshot in linux, but I am not even sure what GUI this is:

VMWare Stopped Working With linuxCNC a While Back

 But VirtualBox seems to work.  Of course, I screwed up enough to reinstall.  I had some memory of the install on the PC in the shop asking me to create a username and password.  It does not seem to under VirtualBox.

I see why now.  I was running Live not Install.  It is not terribly reliable on boot.

It looks like I need to reinstall and then: 

sudo useradd -m clayton

sudo passwd clayton