units-filter: 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/units-filter - from package: units-filter
/var/lib/wims/public_html/bin/units-filter - from package: wims

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

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