ppmdmkfont: 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/ppmdmkfont - from package: netpbm-progs

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

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