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I prepared all the physical parts of my new Air Gapped PC. I want the best recommendation for the software side, should I install tails (which one?) or install any Linux open source OS, download electrum on online device, use USB to instill it

It doesn't matter which trusted unix OS you are going to install.
For ease, stay with the most used/reputable ones (Debian, Ubuntu, Tails, Manjaro, ...). But you can use whatever you want as long as you verify its authenticity and trust its developers (no hannah montana linux or other meme OS).

Then install electrum via an USB downloaded from your online device, yes. But make sure to verify its authenticity (on the offline PC) before installing it.

Since you are using it airgapped I think that tails is best: it has Electrum on it and a couple of other tools too and you don't have to to much (maybe persistent storage if you don't want to enter the seed every time).
The only cases you should use another distro would be:
* if you have another distro you prefer/you are more comfortable with
* if at some point Tails doesn't update in time to "new enough" Electrum (it has happened at some point before Electrum 3.3.4)

This being said, I'd use the newest Tails to have the chance to a new enough Electrum.

Whatever you do, make sure that:
1. The cold storage stays offline (no wifi and no utp cable either)
2. The seed stays safe, on paper, steel, whatever...

If there is some new feature in a newer version of Electrum you are desperate to use, or we see a repeat where older version of Electrum are prevented from connecting to any servers, you can still use Electrum on Tails prior to it being updated in the Tails package by downloading the Linux Appimage from https://electrum.org/#download.

If you are using persistent storage with your Tails, then it should be as easy as opening your old wallet files with the Appimage version of Electrum. If you are not using persistent storage, then you would just recover from your seed phrase as you normally would.

More details here: https://electrum.readthedocs.io/en/latest/tails.html

You're right. I was so focused on convenience I've missed this. (Also the truth is that I've used Tails mostly without persistent storage on.)
Thanks for the completion/fix.

Thanks to everyone. As I mentioned in a previous topic Is Fomat OS and reinstalling it safe? Electrum Cold storage (https://bitcointalk.org/index.php?topic=5312870.msg56209614#msg56209614), I cannot buy a hardware wallet and now this is what I got so far:


Hardware:

• Physically Remove Wi-Fi, ethernet, hard disk and keep two USB port.
• USB Flash Drive 32 GB.
• Another 8 GB USB Flash.

Software:

• Ubuntu OS last verison PGP verified
• Electrum wallet PGP verified

I will boot from USB and try Ubuntu.
Insert 8 GB USB install Electrum.
Extracting the public key.
Sign the transaction.
Broadcast the transaction.

Remove Boot flash and back to normal parts.


Is this plan safe?

I think that you either wrote it wrong, either I'm understanding it wrong.
The "cold storage" Electrum should never go online, still you seem to broadcast tx from it.

So if possible, I'd put Electrum onto the Ubuntu stick too and keep the smaller stick for transport (if that's not possible, consider a 3rd stick for transport).
After the offline Electrum is running, copy onto the transport stick the Master Public Key and shut down Ubuntu.

On your usual OS you make a watch only wallet from that Master Public Key, that's where you create transactions, that are exported to the transport stick.
Ubuntu is loaded up again, tx is loaded from transport, signed and saved back to transport and Ubuntu down again.
On your usual OS you load from transport the signed tx and broadcast it.

I wrote as the "airgapped pc" is the same as the normal pc and you switch between them. If there are 2 different physical PCs it is much easier.

Sorry for that. I summarized the stages of cold storage, but I will mention them in detail:

• Booting from flash (because i removed hard drive)
• click on try Ubunutu
• Install electrum wallet from other USB.
• Extracting the public key and using the phone to conduct the transaction. Hot wallet
• Sign the transaction (I will export the file using QR code or save it to my 8 GB USB flash)
• Return the file to the hot wallet to broadcast it.

After finishing, I will remove the two USB and put the hardware back ( wifi, ethernet and hard disk) on again.

I will repeat it every time I need to send coins.

Now it looks good to me too.

Just be aware that if you aren't using persistent storage, and are going to reinstall Electrum from scratch every time you use it, then you will need to recover from your seed phrase every time you want to make a transaction. In my experience, people who do this tend to have their seed phrase stored on site, somewhere easily accessible, and usually in a raw unencrypted format. The physical security of your seed phrase at this point becomes your weakest link. Your other option is to save your Electrum wallet file on the same USB as your Electrum download, but make sure your wallet file is encrypted if you do this.

If using cameras to transfer QR codes, for extra paranoia unplug/disable/cover them when not in use, especially when entering your seed phrase.