unihexgen: 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/unihexgen - from package: unifont-bin

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