tkjpeg: 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/tkjpeg - from package: perl-Tk

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

On Debian possible default full paths are:

/usr/bin/tkjpeg - from package: perl-Tk

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

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