President Jacob Zuma says he is willing to testify at an inquiry into the multi-billion rand arms deal.

"Of course, anybody called will have to go to the commission to testify whatever you know and whatever you don't know," Zuma said at a question-and-answer breakfast hosted by The New Age newspaper in Cape Town on Tuesday.

He told his audience many people had the impression that "you know a lot when you know nothing".

In September, Zuma announced a commission of inquiry into the arms deal.

Zuma himself was once charged with corruption after his financial adviser Schabir Shaik, who had a tender to supply part of the arms requirements, was found to have facilitated a bribe for Zuma from a French arms company which was part of the deal.

Shaik is on medical parole after being sentenced to jail for 15 years.

The charges against Zuma were withdrawn shortly before he became president due to alleged interference in the investigation.

Zuma was on Tuesday also asked about his sacking of senior public officials, renovations to the presidential residence and his thoughts on the execution of former Libyan leader Muammar Gaddafi.

On his firing of officials, Zuma said it was impossible to know how people would perform when they were appointed to public office.

"Once a person is in the job then the reality comes. You can't say that because I made a choice I better stick to it. You want to see things happen," he said.

Last week, Zuma fired Cooperative Governance and Traditional Affairs Minister Sicelo Shiceka and Public Works Minister Gwen Mahlangu-Nkabinde, and suspended police chief General Bheki Cele.

Shiceka was alleged to have spent about R600 000 of taxpayers' money on un-sanctioned luxury travel, including overseas visits to a girlfriend imprisoned in Switzerland for drug smuggling.

Mahlangu-Nkabinde was found guilty by the Public Protector of wrongdoing for her role in a South African Police Service lease deal.

Cele was suspended with full pay, also in connection with his role in the leasing case.

On his official residences, Zuma said if he could, he would override decisions about multi-million rand renovations made to presidential houses.

"I wish I was the one who took decisions about renovations of presidential residences," Zuma said.

"Those are taken by specific departments without consulting with me. You don't even know how much it is. You only see it in newspapers.

"I have no problem as president to live in my own simple house."

Last month, the public works ministry gave Parliament supposedly incorrect information about the R170-million cost of renovating Zuma's official residence in Pretoria.

However, it emerged that the proposed renovations had been cancelled in March.

Zuma said he was often frustrated at the slowness of the government.

"Government is very slow in doing things," he said.

"If there is a form to be signed, they will do it tomorrow. If I could change that I would be very happy."

When asked about Libya, he said the execution of Gaddafi had created an uneasy feeling.

It would have been better for Libyans if Gaddafi had been arrested and tried so that questions could be answered about how he had run the country for 41 years.

"In [the] world of human rights today there are courts to try those who are committing certain kinds of crime," Zuma said.

"It has created an uneasy feeling about the situation in Libya."

Zuma had words of praise for Lindiwe Mazibuko, who was elected as the Democratic Alliances' parliamentary leader.

"I think it is an indication that our democracy works, as well as empowerment of women works, regardless of the background they come from."

Mazibuko was elected to the position last week, trouncing incumbent and highly experienced Athol Trollip.

"I think the fact that you have an experienced male person who was a contender being defeated by a young lady goes a long way to show that democracy works in this country," Zuma said.