In this case , it will simply print the line, but if you need to do an operation on the text , just insert your code into the while loop.
The version 5 is particularly desirable since a new layout engine for the dashboard has been developed, and is quite powerfull !
So to update your install of Grafana from 4 to 5 you need to launch several command with root or a privileged user.
The service should automaticly restart when the update is done , but check that it is running with :
service grafana-server status
You should see something like this
? grafana-server.service – Grafana instance
Loaded: loaded (/usr/lib/systemd/system/grafana-server.service; disabled)
Active: active (running) since ven. 2018-04-20 17:47:41 CEST; 1 day 22h ago
If you use a Linux box to display some infos in a public space , you might not have the possibility to connect a mouse and keyboard every time you need to click on the page.
For example, at work we use a TV to display some metrics with grafana,
Sometime, when we reboot the machine , the identification cookie will be outdated and the browser will land on the authentication page instead.
Since the machine has no keyboard and mousse attached this cause some issues , .
So I’ve used the tool xdotool that allow a privileged ssh user or a script to interact with the mouse and keyboard
An important step is to select the screen on witch you want to send mouses clicks and keystrokes.
After that lets say your screen is displaying a full-screen browser with a login page ,
By default the cursor is already in the login form.
for the example , the login/password are going to be admin/admin
you are now logged and you dashboard will display
When you are spending your day in the terminal , you will find that navigating using only the arrows keys although fine at the the start will frustrate you because it’s quite slow.
Bash come with a lot of keyboard shortcuts design to gain precious time.
CTRL+A # will move the cursour to the beginning of the line
CTRL+E # moves to end of line
CTRL+C # halts the current command and back to prompt
CTRL+D # deletes one character backward or logs out of current session, similar to exit
CTRL+K # deletes all the text forward to the end of the line
CTRL+L # clears screen and redisplay the line
CTRL+R # searches history entering keyword ,
CTRL+T # transposes two characters
CTRL+U # kills backward from point to the beginning of line
CTRL+W # kills the word behind the cursor
i’ve put in bold the shortcuts that i use every day , i don’t use CTRL+A and CTRL+E because the keyboard has keys that are foing the same thing.
In bash , it is common to have to do some action on a numéric serie of files , like deleting or renaming ,
Using brace expansion you will be able to générate a single line that will act on multiple targets ,
For our example , let’s think about a list of ten files
in the simple case where i want to delete the complete list of files, i just have to run de command,
The 10 files will be deleted, but , this is not practical if you want to keep the last file , and delete the other nine,
In that case we can use a usefull tool called brace expansion,
To delete the files 1 to 9 , i just have to run in my bash terminal!
This last one is extremely practical , I use it very often in a lot of different uses cases.
But in other cases , you may want to delete even on odd files , or one every three files,
This is also doable with braces expansions
il you need to run a script unattended and wish to log the output of that script you must already know that you can simply do
the problem with that is you will not log the error messages , only the output messages ,
the error are going to be displayed on the terminal but , not logged
and the error message are often as important as the output message , we do not want to dismiss them from the log ,
the solution to that issue is to run the script using this
With this , both the output will be logged in to the log file.
As you know if you own the orange pi zero, the board run very hot. Running it without an heat sink is not really possible if your board is doing anything other than idling
and even with an heatsink you will encounter throttling if your application is a little intensive.
In an other article I managed to get a fan running controlled by the gpio’s.
A cron check every minute the cpu temperature, if it’s above a set temperature, the fan turn on.
If it’s under, the fan turns off.
The first time I did that project it was on my first orange pi zero. I made some mistakes in my wiring and, because of that, the fan only received 2.5v, it was spinning very slowly, and I was obliged to do some bash trickery to get the fan to start.
My original orangepi zero was lost during an apartment change.
I decided to order a new one and this time, I wanted to do the best work I could to integrate the fan and heatsink.
I found an acrylic case for the orange pi zero on aliexpress.
And after receiving my orange pi zero, I saw the board was a new revision, it was running even hotter than my previous orange pi zero.
Few days after receiving the board, the case arrived. It was very pretty but it was blocking any air circulation. And the heatsink had no medium to dissipate the heat since the air was hot and not circulating around the metal.
The CPU temperature rapidly ascended to 80°c.
I own several old fans disassembled from old graphics card, and one of the small fans was just the perfect size. I cut a circular hole in the top acrylic plate so the air from the fan could enter and go trough the radiator fins. The air should after exit from a void in a face of the case were optional usb port are placed.
How to use that fan?
The problem with gpio’s is that they only push very weak current and volts (3.3v). You cannot run a fan directly from a gpio.
But you can use a gpio to control an electronic switch (a transistor) that will be able to run the fan
You should use a npn transistor. They are the most common and cost next to nothing. You will find them for free when you tear down old broken power supply.
To turn on and off your switch, you just have to send 1 or 0 on it’s base.
A great way to control the gpio’s of the opi zero is with the help of that library called WiringPI
you will find instructions on how to install the library on the github page.
after installation lauch the command gpio readall
i chose the gpio.7 to control my fan ,
conveniently the gpio 7 is placed in the 7th place on the board , and his wPi alias is also 7
as you can see in the attached capture it’s not always the case !
i then solder my fan and transistor following this diagram :
To continue , i must write a script that check for the cpu temperature , and activate the fan if the cpu temperature is above a certain set threshold.
then , using crontab , set this script to launch every minutes.
add the line * * * * * /root/fan-control.sh to your cron jobs , using the command crontab -e
thanks to this script your fan should automatically launch when your Orange is charged , and stop when it’s return to idling.
When installing grafana and influxDB. I encountered the folowing issue
The service of grafana and influxDB where not starting .
I checked using rcconf that my service where enabled , and they where !
I then tried sysv-rc-conf and my service where correctly configured !
the services had absolutely no issue starting when called manually and started fine !
this line was telling me that the service startup was disabled !
after seaching a bit on the web ,the solution to this issue is using systemctl to enables the services.
If you have to insert multiples values in an influxdb database. You can use curl and insert the values one at the time.
But there is a better way like in this example
Let’s say you want to insert your tree loadaverage values in you influxdb database.
First put them into variables using these 3 lines.
Then using this curl line, insert them all at once in your influxdb database
if you follow what’s new in the SBC world. You must know Xunglong Orange pi, they are a Chinese manufacturer known for making very cheap sbc’s based on Allwinner chip’s.
One of their most interesting sbc’s was the orange pi zero. It was small, powerful, and was ideal for a small headless server. (still available)
It was extremely cheap: less than 10€ but was plagued with some issues like very poor wifi stability, and poor software support from the manufacturer and, only 100mbps on the Ethernet port.
Now Xunlong has come up with an improved version of this board.
- The wifi chip is now a well supported Realtek RTL8189FTV
- The Ethernet port is now capable of 1Gb/s transfer rate
- The cpu is improved with an Allwinner H5
- The layout stay exactly the same so case are compatible.
I’ve already ordered one of these boards. At 16,02€ including shipping
It’s available at Aliexpress