Use a terminal or comm server
Risk of solution: Non-risk operation

A terminal server, for example an AR router with 8AS, 1SA, or 2SA boards, can connect directly to the device Console using asynchronous serial ports and the Reverse Telnet function.
This will provide access to the BootROM menu where the user can delete the startup system software and download a new software package from a network FTP server.
A terminal server will also allow access to the device in case the upgrade fails and remote troubleshooting is required.

Delete redundant files
Risk of solution: Non-risk operation

In many situations it is possible to ensure sufficient free space by simply deleting files that are not required for normal device operation.
- Delete all patch files; use patch deactive all to disable any loaded patches and patch delete all should delete patch files from the system.
- Delete web portal files  (for example S5300EI-V200R003C00.001.web.7z)
- Delete logs from logfile or syslogfile and resetinfo folders
It is recommended to make backups on an FTP server and make note of the device name and SN in case the logs are needed for any future troubleshooting
- Use the command reset recycle-bin to permanently delete files from the recycle bin

Tip: use delete /unreserved to bypass the recycle-bin

Delete the current system software
Risk of solution: Risky operation

Most devices do not allow the user to delete the next startup system software.
The following diagnostic command can be used to unload the system software, which will allow the user to delete the software file remotely:
[Huawei] diagnose
[Huawei-diagnose] undo startup system-software
[Huawei-diagnose] return
<Huawei> delete /unreserved S5300EI-V200R003C00SPC300.cc

The device will continue to run with the software loaded in RAM, and the user can proceed to upload a new version.
Warning: if the upgrade fails or there is a power outage or if the device is rebooted accidentally without a new software package installed, it will become inoperable.