pgmtopbm: 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/pgmtopbm - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/pgmtopbm - from package: netpbm

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

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