pbmtoepsi: 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/pbmtoepsi - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/pbmtoepsi - from package: netpbm

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

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