condor_restart: 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/sbin/condor_restart - from package: condor

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

On Debian possible default full paths are:

/usr/sbin/condor_restart - from package: htcondor

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

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