Linux - Convert Putty private key to OpenSSH keys

If you are migrating your keys from Putty Windows to linux it won't work with the OpenSSH client and you will be able to convert them with the steps below :

tiago@linux-desktop ~/D/s/T/H/p/SSH> sudo apt install putty
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
  putty-tools
Suggested packages:
  putty-doc
The following NEW packages will be installed
  putty putty-tools
0 to upgrade, 2 to newly install, 0 to remove and 0 not to upgrade.

use the command below to convert the key :

tiago@linux-desktop ~/D/s/T/H/p/SSH> puttygen hv2-ssh_private_key.ppk -O private-openssh -o hv2-ssh-openssh.key
Enter passphrase to load key: 
tiago@linux-desktop ~/D/s/T/H/p/SSH> ll
total 16K
-rwxr-xr-- 1 tiago tiago  732 May 24  2020 authorized_keys
-rw------- 1 tiago tiago 3.3K Jun  2 14:41 hv2-ssh-openssh.key
-rwxr-xr-- 1 tiago tiago 2.7K May 24  2020 hv2-ssh_private_key.ppk
-rwxr-xr-- 1 tiago tiago  829 May 24  2020 pub.key

-O - specify output type:
          private             output PuTTY private key format
          private-openssh     export OpenSSH private key
          private-openssh-new export OpenSSH private key (force new format)
          private-sshcom      export ssh.com private key
          public              RFC 4716 / ssh.com public key
          public-openssh      OpenSSH public key
          fingerprint         output the key fingerprint

-o - specify output file