airspy_spiflash: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/airspy_spiflash - from package: airspy

You may install the required package with command apt-get install {package}
Error in other languages:
airspy_spiflash: bevel nie gevind nie
airspy_spiflash: comandă negăsită
airspy_spiflash: comando não encontrado
airspy_spiflash: commande introuvable
airspy_spiflash: command not found
airspy_spiflash: käsku ei ole
airspy_spiflash: không tìm thấy lệnh
airspy_spiflash: komanda nerasta
airspy_spiflash: Kommando nicht gefunden.
airspy_spiflash: kommandot finns inte
airspy_spiflash: komut yok
airspy_spiflash: nie znaleziono polecenia
airspy_spiflash: níor aimsíodh an t-ordú
airspy_spiflash: no se encontró la orden
airspy_spiflash: no s'ha trobat l'ordre
airspy_spiflash: opdracht niet gevonden
airspy_spiflash: parancs nem található
airspy_spiflash: perintah tidak ditemukan
airspy_spiflash: príkaz nenájdený
airspy_spiflash: příkaz nenalezen
airspy_spiflash: команда не найдена
airspy_spiflash: командата не е открита
airspy_spiflash: 命令找不到
airspy_spiflash: コマンドが見つかりません