SSH into legacy.pmc.ucsc.edu or any other managed Linux machine on the PMC network
e.g. from a Mac or Linux terminal type: ssh your_user_name@legacy.pmc.ucsc.edu
At the command prompt type the command: passwd
You will be prompted for your old or temporary password once and for your new password twice.
Note- while typing the passwords, no visual indications will be shown. This is done for security purposes so that someone peaking over your shoulder won't be able to tell how long your password is.