sdoc-merge: 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 Debian possible default full paths are:

/usr/bin/sdoc-merge - from package: ruby-sdoc

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