dogtail-detect-session: 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/dogtail-detect-session - from package: dogtail

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

On Debian possible default full paths are:

/usr/bin/dogtail-detect-session - from package: python-dogtail

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

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