thinkjettopbm: command not found

Have You tried accessing the binary with the full path?

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/thinkjettopbm - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/thinkjettopbm - from package: netpbm

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