readproctitle: 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 Debian possible default full paths are:

/usr/bin/readproctitle - from package: daemontools

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

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