apertium-rehtml: 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/apertium-rehtml - from package: apertium

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

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