Upslug2 is a command line program intended to allow the upgrade of a Linksys NSLU2 (Network Storage Link for USB 2.0 Disk Drives) firmware to new or different versions. When a NSLU2 in the local network is put in upgrade mode, upslug2 can connect to it and upload a new firmware.

upslug2 will accept a full firmware image but it can also upgrade the flash from individual files holding the kernel, ramdisk and root filesystem. upslug2 provides status information during the upgrade process and verifies the written image after the upgrade.