i3bar: 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/lib/debug/usr/bin/i3bar - from package: i3-wm-dbg
/usr/bin/i3bar - from package: i3-wm

You may install the required package with command apt-get install {package}
Error in other languages:
i3bar: bevel nie gevind nie
i3bar: comandă negăsită
i3bar: comando não encontrado
i3bar: commande introuvable
i3bar: command not found
i3bar: käsku ei ole
i3bar: không tìm thấy lệnh
i3bar: komanda nerasta
i3bar: Kommando nicht gefunden.
i3bar: kommandot finns inte
i3bar: komut yok
i3bar: nie znaleziono polecenia
i3bar: níor aimsíodh an t-ordú
i3bar: no se encontró la orden
i3bar: no s'ha trobat l'ordre
i3bar: opdracht niet gevonden
i3bar: parancs nem található
i3bar: perintah tidak ditemukan
i3bar: príkaz nenájdený
i3bar: příkaz nenalezen
i3bar: команда не найдена
i3bar: командата не е открита
i3bar: 命令找不到
i3bar: コマンドが見つかりません