imjoin: 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 Debian possible default full paths are:

/usr/bin/imjoin - from package: im

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

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