cyr_df: 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/lib/cyrus/bin/cyr_df - from package: cyrus-common

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

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