reindexdb: 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/reindexdb - from package: postgresql

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

On Debian possible default full paths are:

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

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

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