fa2htgs: 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
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

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/fa2htgs - from package: ncbi-tools-bin

You may install the required package with command apt-get install {package}
Error in other languages:
fa2htgs: bevel nie gevind nie
fa2htgs: comandă negăsită
fa2htgs: comando não encontrado
fa2htgs: commande introuvable
fa2htgs: command not found
fa2htgs: käsku ei ole
fa2htgs: không tìm thấy lệnh
fa2htgs: komanda nerasta
fa2htgs: Kommando nicht gefunden.
fa2htgs: kommandot finns inte
fa2htgs: komut yok
fa2htgs: nie znaleziono polecenia
fa2htgs: níor aimsíodh an t-ordú
fa2htgs: no se encontró la orden
fa2htgs: no s'ha trobat l'ordre
fa2htgs: opdracht niet gevonden
fa2htgs: parancs nem található
fa2htgs: perintah tidak ditemukan
fa2htgs: príkaz nenájdený
fa2htgs: příkaz nenalezen
fa2htgs: команда не найдена
fa2htgs: командата не е открита
fa2htgs: 命令找不到
fa2htgs: コマンドが見つかりません