devhelp: 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/devhelp - from package: devhelp

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

On Debian possible default full paths are:

/usr/bin/devhelp - from package: devhelp

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

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