pg_receivexlog: 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/lib/postgresql/9.4/bin/pg_receivexlog - from package: postgresql-client-9.4
/usr/bin/pg_receivexlog - from package: postgresql-client-common

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

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