tiffmedian: 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/tiffmedian - from package: libtiff

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

On Debian possible default full paths are:

/usr/bin/tiffmedian - from package: libtiff-tools

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

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