The following error may occur while attempting to upgrade JunOS with newer version.
In this particular case, it occurred on a EX4300 running 18.4R3-S1.3 (and the target version was 19.4R3-S14.1).
Due to limited flash memory size and constantly increasing size of newer software version, this issue may become increasingly common on some more entry level devices.
I recall a known “bug” report claming that this is fixed in newer versions, but this also happened on the same device upgrading to v21.4R3-S11.3 as well.
Here is the full console output of the issue :
root> ... add jinstall-ex-4300-19.4R3-S14.1-signed.tgz no-copy NOTICE: Validating configuration against incoming-package.tgz. NOTICE: Use the 'no-validate' option to skip this if desired. The /var/tmp filesystem on JUNOS is low on free disk space. This package requires 3MB more space free. ERROR: Please use the request system storage cleanup command to delete old files from /var/tmp
Running the suggested “request system storage cleanup” may not fix the issue (it did not in my case), there was still not enough space.
Deleting the hidden folder “.schema-cache” under /var/tmp was the solution for me. There is no risk deleting this folder as JunOS will automatically re-create it. Simply delete it as followed :
rm -rf /var/tmp/.schema-cache
Then attempt the upgrade again.