unihex2png: command not found

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/unihex2png - from package: unifont-bin

You may install the required package with command apt-get install {package}

Error in other languages:
unihex2png: bevel nie gevind nie
unihex2png: comandă negăsită
unihex2png: comando não encontrado
unihex2png: commande introuvable
unihex2png: command not found
unihex2png: käsku ei ole
unihex2png: không tìm thấy lệnh
unihex2png: komanda nerasta
unihex2png: Kommando nicht gefunden.
unihex2png: kommandot finns inte
unihex2png: komut yok
unihex2png: nie znaleziono polecenia
unihex2png: níor aimsíodh an t-ordú
unihex2png: no se encontró la orden
unihex2png: no s'ha trobat l'ordre
unihex2png: opdracht niet gevonden
unihex2png: parancs nem található
unihex2png: perintah tidak ditemukan
unihex2png: príkaz nenájdený
unihex2png: příkaz nenalezen
unihex2png: команда не найдена
unihex2png: командата не е открита
unihex2png: 命令找不到
unihex2png: コマンドが見つかりません