User names with leading underscore

[pbw]

Some of the system-type accounts have been created with a leading underscore, e.g. _mysql, while others have been created without one, e.g. postgres.

What is the significance of the _NAME user names? Are these users normally identified in applications with as NAME, that is, without the underscore?

 

[toMACsh]

Created by whom? Ask that person...

Maybe to get them to appear out of order in an alphabetical list?

 

[pbw]

They're pretty common.
_uucp
_lp
_postfix
_mcxalr
_pcastagent
_pcastserver
_serialnumberd
_devdocs
_sandbox
_mdnsresponder
_ard
_www
_eppc
_cvs
_svn
_mysql
_sshd
_qtss
_cyrus
_mailman
_appserver
_clamav
_amavisd
_jabber
_xgridcontroller
_xgridagent
_appowner
_windowserver
_spotlight
_tokend
_securityagent
_calendar
_teamsserver
_update_sharing
_installer
_atsserver
_ftp
_unknown
_softwareupdate
_coreaudiod
_screensaver
_locationd
_carddav
_trustevaluationagent
_timezone
_lda
_cvmsroot
_usbmuxd
_dovecot

 

[toMACsh]

Some of the system-type accounts have been created with a leading underscore,

Do you mean user accounts, as in System Preferences > System > Accounts ?

Again,

Created by whom?

If not the above, where do you see these?

 

[pbw]

In a terminal
$ cat /etc/passwd

That shows all of the accounts known at system startup.