exo-open: 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/exo-open - from package: exo

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

On Debian possible default full paths are:

/usr/bin/exo-open - from package: exo-utils

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

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