rsyncusers: 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/bin/rsyncusers - from package: mirrorbrain-tools

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

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