atktopbm: 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/atktopbm - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/atktopbm - from package: netpbm

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

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