This article explains what must be done when a Junos OS upgrade in SRX devices fail with the following warning message:

This base version of JUNOS will not properly support this package

SRX320 upgrade fails with the following messages:

Installing package '/altroot/cf/packages/install-tmp/junos-15.1X49-D190.2-domestic' ...
Verified junos-boot-srxsme-15.1X49-D190.2.tgz signed by PackageProductionEc_2019 method ECDSA256+SHA256
Verified junos-srxsme-15.1X49-D190.2-domestic signed by PackageProductionEc_2019 method ECDSA256+SHA256
sed: /etc/db/pkg/junos/+COMMENT: No such file or directory
 
WARNING: This base version of JUNOS will not properly
WARNING: support this package. Please install base OS
WARNING: JUNOS 6.4 or newer first. You can do this via
WARNING: a jinstall package or install-media.

This is because a soft link is missing.

root@SRX320-r010-A17_35% ls -l /etc/db/pkg/junos
ls: /etc/db/pkg/junos: No such file or directory

To resolve the issue, create the soft link as follows:

root@SRX320-r010-A17_35%ln -s /pkg/junos /etc/db/pkg/junos

root@SRX320-r010-A17_35% ls -l /etc/db/pkg/junos
lrwxrwxrwx  1 root  wheel  10 Sep 16 16:03 /etc/db/pkg/junos -> /pkg/junos

2021-04-14: Corrected the command to create softlink ( From ls -s /pkg/junos /etc/db/pkg/junos to ln -s /pkg/junos /etc/db/pkg/junos)