cleandb.sh: 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 CentOS possible default full paths are:

/usr/share/roundcubemail/bin/cleandb.sh - from package: roundcubemail

You may install the required package with command yum install {package}

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