From The Free On-line Dictionary of Computing (19 January 2023):
system administration
admin
sysadmin
system administrator
<job> Activities performed by a system administrator (or
"admin", "sysadmin", "site admin") such as monitoring security
configuration, managing allocation of user names and
passwords, monitoring disk space and other resource use,
performing backups, and setting up new hardware and
software.
system administrators often also help users, though in a large
organisation this may be a separate job.
Compare postmaster, sysop, system management, systems
programmer.
[Other tasks?]
(1999-05-02)