sxiv: 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/bin/sxiv - from package: sxiv

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