join: 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/join - from package: coreutils

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

On Debian possible default full paths are:

/usr/bin/join - from package: coreutils
/usr/lib/plan9/bin/join - from package: 9base
/usr/lib/seqan/bin/join - from package: seqan-apps

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

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