This can be accomplished with the ch_admin_passwd binary.
[root@plesklinux root]# cd /usr/local/psa/admin/bin/
[root@plesklinux bin]# ./ch_admin_passwd --help./ch_admin_passwd: Utility to set Plesk adminstrator’s password
Gets password from the environment variable PSA_PASSWORD
Password should be from 5 to 16 symbols and should not contain login name,
whitespace, quotes or national characters
Usage: ./ch_admin_passwd
-h, –help
display this help and exit
We must export the variable before running the binary. We will unset the variable when we are done.
[root@plesklinux bin]# export PSA_PASSWORD='newpass'
[root@plesklinux bin]# echo $PSA_PASSWORD
newpass
[root@plesklinux bin]# ./ch_admin_passwd
[root@plesklinux bin]# export PSA_PASSWORD=
[root@plesklinux bin]# cat /etc/psa/.psa.shadow
newpass
[root@plesklinux bin]#