Below error observed while pushing the image to upgrade the EX3400 switch
labroot@root> request system software add /var/tmp/"junos-arm-32-21.4R3-S7.6.1.tgz"
Removing /var/log/wtmp.0.gz
Removing /var/log/messages.0.gz
Removing /var/log/interactive-commands.0.gz
setting unlink by default.
contents/jail-runtime.tgz: truncated gzip input
tar: Error exit delayed from previous errors.
/usr/libexec/ui/package: /var/tmp/junos-arm-32-21.4R3-S7.6.1.tgz: invalid file
ERROR: No packages added
Copied file name to switch was incorrect and hence while pushing the image to switch, image name was enclosed within the brackets.
>request system software add /var/tmp/"junos-arm-32-21.4R3-S7.6.1.tgz"
1. Checked the JUNOS file name copied in /var/tmp directory.
2. Validated the file and re-downloaded the correct image form support portal : https://support.juniper.net/support/downloads/