Going down

The problem with this part of the city is the slopes. You need to be familiar with them or you will always end up going up instead of down, or down instead of up. And it very annoying, of course, specially if you are completely wasted.

The guys didn’t complain at all, they followed me out of our building to the street while mumbling something about the decoration of the flat. I was actually concentrated on going down properly and getting quickly the main stream to Hedgehogs’ corner. First steps were always crucial: if one diverges just 5 meters to the left, one can end up climbing a crazy mountain instead of softly sliding down away, enjoying the gravity of your own weights. I told the brothers.

– Hear me out, please – they immediately stopped discussing what I assumed was the decoration they wanted for the flat – probably as you previously observed the space-time geometry locally has a “z” instability. You can deduce the consequences of it, if you didn’t experience before. If you’re so kind to follow me, we’re going to use the minimum energy path to go all the way down to Hedgehogs’ corner.

– Thanks for guiding us man. You know how difficult it is for newcomers to work out how to move here. – Paper man was definitely the leader of the couple. By the way, I need to remember to find the right moment to ask them for their names. Or did they already told me? – I really miss my handy. And the social networks. And the internet, all together.

– You don’t miss that. – I stop going down and turn back, to look into their eyes. – We were slaves, you know? We were working for the profit of an oligarchy that only wanted to show up to be adored, to be said how cool they were that they had 500 billions more than the other guy. That they had enough money to buy a school for this or that, an university, of for all that matters, a country. They were, all together, owning the fucking planet. – I take one of my precious cigarettes and I light it. –  So yeah, don’t miss it. Here in the city we value you for what you’re able to do, not for what you own, or for who are you related with. You can get a reward corresponding to your abilities, not to the economy you happen to be embroiled in. – They now stare at me with a weird face. I give a puff and throw the smoke to them, despectively, forcing an answer.

– What the hell are you talking about? – Pasta Glasses is trying to be friendly and he looks genuinely shocked due to my little speech. – After the war, nobody was even able to say he was owning a fucking potato… because there were no potatoes! – Pasta Glasses was not angry, just obviously enjoying a lot lecturing me. – That was like a hundred years ago. – I throw my burning butt, maybe a little bit more violently that I should have. The war. When I left, there was no war. The menace was there, right, but nobody thought that as a real possibility. – I see. – Now Paper Man is back with the leading voice. – Sorry sensei, but you’re outdated. The System may not be the best form of government, but we were getting close to achieve something new. We were. Now we’re here. And with no easy way back, as far as I understood. So let’s assume it and be a part of it, be the best on it.

– A pragmatic approach. But it’s OK, provided you know where you stand.- I manage to add.- This way, please. – I point the on direction of the speed line to the Hedgehogs’. We walk in silence until reaching it. Then, to the left, until we’re in. The road looks curved around us, like a water channel or a half pipe. I start walking.  The building move out of my sight at a constant speed that I estimate of around 30 Km/h while I’m just walking… so in a couple of minutes we’re there. Hedgehogs’ corner.  I step out of the speed way, to reach the small square. – Now guys, time to test your mathematical abilities.

Posted in aliens, bits, fantasy, friends, new dreams, unpublished, yellow earth | Leave a comment

A very complex integral

– Could you please help us solving this integral?
I could’t believe my ears. I opened the door because they looked innocuous thought the sight glass. There they were, two nerd-looking teenagers, one of them practically rubbing in my face a paper with a complicated triple integral. The second one adjusted his glasses over his nose, while trying not to drop his pile of books. Some of the titles were readable from my vantage point of view.  Advanced Calculus. Numerical Recipes. Numerical Methods. All the classics. As for instinct, I reached my pocket, but my mobile phone was missing. Of course it was. Why should not be?

– Guys, calm down. Please elaborate. What’s going on?
– We were asked to to this …math …to be allowed to stay in. Aren’t you the famous physicist? – I’m flattered, but I try not to show it. I am just good visualising the solution to the problems. – We were thinking… that you will teach us. – The one with the glasses finished the sentence his friend with the paper started. So cute.

– Right. Don’t panic. Let me see. – I have a look. Damn, it’s not easy: maybe it requires a double substitution. It’s far, far more difficult than the ones I was asked to solve up to now. I wonder for what is going to be used… – Sorry to disappoint you, but it has no easy solution. Are you in hurry?
– Yes we are! – Paper Man practically shouted. On the other hand, Pasta Glasses was trying to make a sad face. – We really want to stay here. We’re no artists, neither entertainers, this is definitely our building. Of course we could try to go to a lower level… maybe school’s level will be better for us? – I look into the eyes of my future neighbours, trying to evaluate if they’re just playing with me.

– OK, ok. Don’t worry. I will speak to the building manager to delay your payment. – I realised I was feeling pity for the couple, but this is me, I’m a piteous person. I see a stray cat, I give him milk. I find a problem, I try to solve it. It’s the Curse of the Physicist. – Let me see those books. Yes, leave your calculations over the table. – They smile to me. I wonder how old are they, twenty, thirty? Here we don’t age, so they can be sixty as far as I know. But it’s OK, no stress allowed. We’re living the American Dream.  – Are you familiar with the neighbourhood already? – They nod. I look out, dusk is coming, and I’m a little bit hungry. Or I will say thirsty. – How good are you on basic calculus?

– We passed the basic education… -Paper Man seems to be the leader of the pack. Pasta Glasses continues. – We just started Math at the University before… arriving here… so we thought we could apply for a flat on this building…
– Boys, calm down. Of course you did right. This is the best place to challenge your mind. Why are we here? What is this city? Where is the rest of the world? – They look at me like if they were drinking my words. – We can speak about the future of mankind as we know it, and similar issues, at the Hedgehogs’ corner. But you probably will need to perform some basic math there before getting your drinks. Are you ready? Will you join me?

– Of course we will! – They both smile. What are those two? Brothers? I take my dusty raincoat, a pack of cigarettes, I check that I have my lighter and I push them downstairs.
– Then let’s go!

Posted in aliens, fantasy, fragments, new dreams, unpublished, yellow earth | Leave a comment

OSX su versus sudo

I had this weird problem. I need to run some commands with sudo. But I have a root password, why should I sudo something? The answer is simple: the SU password is not the same than the sudo one. So, as real root, supposing you have the root account enabled, you have more control than the sudo user. And you can give sudo rights to a local Admin account (sudo su will be work with that user’s password) without compromising your root account password. Now the problem will be to teach the user so that he doesn’t mess up with the system functions 😛 …I can’t help you there. Or can I?

Posted in bits, mac, osx | Leave a comment

CONFIG_RETPOLINE=y error on CentOS 7

We need to update our systems. We don’t do it regularly, but when requested by the authority, and this time they requested it due to Specter & Meltdown. So there I am trying to get my rpm for the newest version of GPFS when I stumble upon this error:

make[1]: Entering directory `/usr/lpp/mmfs/src/gpl-linux'
Pre-kbuild step 1...
/usr/bin/make -C /usr/src/kernels/
3.10.0-693.21.1.el7.x86_64 M=/usr/lpp/mmfs/src/gpl-linux clean
make[2]: Entering directory 
arch/x86/Makefile:166: *** CONFIG_RETPOLINE=y, 
but not supported by the compiler. 
Toolchain update recommended.. Stop.
make[2]: Leaving directory 
make[1]: *** [Clean] Error 2
make[1]: Leaving directory `/usr/lpp/mmfs/src/gpl-linux'
make: *** [Clean] Error 1

Technically, I’m compiling the drivers as in this post. Now what? I have two options. I try to update the Toolchain (compiler and so on) or I can have a look to my Makefile. I tend not to alter the systems, but the code, so I go for the second option.  The Makefile lines around the 166 are indeed related with Specter.

# Avoid indirect branches in kernel to deal with Spectre
$(call cc-option,-mindirect-branch=thunk-extern \
# ifneq ($(RETPOLINE_CFLAGS),)
# else
# $(error CONFIG_RETPOLINE=y, but not supported by the compiler. \
Toolchain update recommended.)
# endif

So I simply comment them out and try again. Surprise! It works. Note that it is exactly the same group of line that in the already mentioned post. Can I leave it like this? If I do so, I will be leaving a security hole open, but I’m not the security expert, so I will report it and continue. For the records, we have a firewall between us and the internet, so it will not be a big deal to leave this hole. And, luckily, it turns out that the RPM compiled with a more modern gcc, on an updated machine, can be used. I just wanted to keep a record of the issue. Just in case. Juuuust in case 🙂

Posted in bits, centos, filesystems, GPFS, hardware, linux, programming | Leave a comment

A MATLAB Runtime module

First we download the chosen package from the MATLAB site. Then we unzip it on a test folder and run the provided install script. 5081690_1_4The procedure is quite easy, no programming knowledge is needed. We choose the path to our run time software in a way we  can easily reach it from everywhere: a network folder. On this example, we install it on /net/local/MCR_R2017b/.

The installation takes in my case around 4 minutes. After it we have a sub-folder on MCR_R2017b called v93. That will be our “topdir”. The module that calls this software is like follows.

## modules MCR_R2017b
## MCR_R2017bmodule
proc ModulesHelp { } {
 global version modroot

puts stderr "MCR_R2017b - 
 sets the Environment for using MCR_R2017b"

module-whatis "Sets the environment for using MCR_R2017b "

# for Tcl script use only
set topdir /net/local/MCR_R2017b/v93
set version R2017b
set sys linux86

prepend-path PATH $topdir/bin

# Location in the distribution expected to have an MCR
setenv MCR_ROOT $topdir

prepend-path LD_LIBRARY_PATH 

Now we test it. We’re going to compile a helloworld.m. The file content is below.

function helloworld
 fprintf('\nHello, World!\n')

We go to a client with a MATLAB license to compile it. We use the simplest compilation.

me@matlab-client $ > mcc -m helloworld.m
me@matlab-client $ > ls
helloworld* helloworld.m 
mccExcludedFiles.log readme.txt 
requiredMCRProducts.txt run_helloworld.sh*

As you see, it works, but a lot of other files are generated. To test our executable is independent of MATLAB, we go to another client (normal-client), load the MCR module and run the compile code.

me@normal-client $ > module load MCR_R2017b 
me@normal-client $ > ./run_helloworld.sh 
./run_helloworld.sh <deployedMCRroot> args
me@normal-client $ > ./helloworld

Hello, World!

So it seems to be OK. If you want to check the basics of matlab compilation you can go to this link. We will see now for real, big stuff…

Posted in bits, linux, matlab, modules, slurm | Leave a comment

Sharemouse, a Keyboard Video Mouse sharing solution for Windows and macOS

I have now 3 computers, real ones. And 4 monitors. But OK, let’s say I need them. What I don’t need is to have 3 keyboards and 3 mice. So I looked for a KVM (Keyboard-Video-Mouse) to make my life simpler. If you google KVM, the first entry is usually Synergy. I tried synergy before, and I must say it’s a killer: you have a configuration GUI, where you can input the IP’s and names of the clients, and what you want to share and what not. I saw it gets crazy when there are more than one network address available. I frequently had disconnections and errors, but maybe that’s not your case.

So I decided to follow the geek stuff guide about how to install it. My synergy server is my CentOS 7 test machine. There, I simply do

 yum install synergy

And I end up with synergy. For my mac (High Sierra 10.13.3) is more complicated. First I need to install MacPorts, then I can run

sudo port install synergy

The output on my mac terminal is very long to copy it here. MacPorts installed like 30 packages before going to synergy. Fortunately, you’re asked if you want them. Like this:

The following dependencies will be installed: 
Continue? [Y/n]: y

I assume the installation is not harmful for my brand new mac. I create my synergy.conf as suggested and I launch the server on my CentOS:

synergy-core --server -f -c synergy.conf

I need to write the computer name instead of the IP on the configuration so that it starts without complains. The I go to my mac and I start the client.

synergy -f IP.OF.THE.SERVER
[SOME-DATE] WARNING: failed to connect to server: Connection refused

I wait a little in case the problem is sorted out without further errors, but no, it doesn’t seem to work. Vice versa (server on my mac, client on the CentOS 7) I had no better luck. The problem seems to be linked with the fact that I’m connecting my mac via WiFi, and my CentOS via cable.

You realised that synergy is not the title of the post. It’s because it was not my solution. I simply went to the sharemouse wepbage, downloaded the windows version, the mac version, run the windows exe, then the mac dmg (note you need to give it permissions, but the very program is telling you what to do the first time you run it) and add the mac IP to the windows server. Now I can  move my mouse around and type in my mac with my windows keyboard.

Where’s the catch? If you don’t buy it, you will be reminded you need to buy a license, and you will need to restart it from time to time. That is a minor annoyance, if you ask me. But we will see… at this moment I’m very happy with it 🙂

Posted in centos, hardware, linux, mac, osx, software, windows | Leave a comment

Speed test with iperf on CentOS 7

We’re now having more than one GPFS client hooked up to a 10 GB line. The fact we have a 10 GB network available is not, unfortunately, meaning that we can have that speed, so we need some tool to test the up speed and down speed. This tool is iperf. On this example, we run it between two 10 GB clients. We can install it via yum.

yum install iperf iperf3

I assume you do that on two clients, that I will call master and slave. Once done, I start the server on the master like this.

@master ~ ## > iperf3 -s -i 10
Server listening on 5201

Then I start the client. I copy also the output, that is clearly telling us the down speed.

@client ~ ## > iperf3 -t 10000 -c master
Connecting to host master, port OTHER
[ 4] local X.XX.XX.XXX port SOME-PORT connected 
[ ID] Interval Transfer Bandwidth Retr Cwnd
[ 4] 0.00-1.00 sec 1.09 GBytes 9.35 Gbits/sec 41 911 KBytes 
[ 4] 1.00-2.00 sec 1.09 GBytes 9.40 Gbits/sec 4 1.22 MBytes

Once the client is started, there should be a message on the master. Something like this:

Accepted connection from X.XX.XX.XX, port SOME-PORT
[ 5] local Y.Y.Y.Y port OTHER connected to X.X.X.X port SOME-PORT

To measure the up speed, we simply run it viceversa:

@client ~ ## > iperf3 -s -i 10

@master ~ ## > iperf3 -t 10000 -c client

Thank you very much iperf, you are my only tool!

Posted in bits, centos, GPFS, linux, software, yum | Leave a comment