Ethiopia, nicknamed the Walyas after a native antelope, dismissed Yohannes Sahile last week after conceding 10 goals in two consecutive qualifiers against Algeria. They lie second in Group J, five points behind Algeria.
Gebremedhin, previously manager of Ethiopian Premier League side Defence Forces, signed a five-month deal on Tuesday and needs to ensure maximum points against Lesotho and Seychelles in June and September to hold on to what the Ethiopian Football Federation described as a "mathematical chance" of qualifying.
Besides hosts Gabon, 15 other teams will go through to the finals from 13 groups.
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As a forward, Gebremedhin led the Walyas in 1987 to their first victory in the CECAFA Cup of east and central African nations.
After sealing a spot in the 2013 Nations Cup, their first in three decades, Ethiopia came within two matches of a first-ever World Cup appearance in Brazil two years ago, but their form has since slumped.
(Reporting by Aaron Maasho; Editing by George Obulutsa and Mark Trevelyan)
