sessionStats: command not found

Have You tried accessing the binary with the full path?

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/sessionStats - from package: cjdns-tools

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