ssid: 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/ssid - from package: suckless-tools

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

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