sushell: 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

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:

/sbin/sushell - from package: initscripts

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